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1.
J Med Virol ; 95(5): e28767, 2023 05.
Article in English | MEDLINE | ID: covidwho-2327255

ABSTRACT

This study aimed to evaluate the effects of different vaccine regimens on mild and asymptomatic infections with SARS-CoV-2 Omicron BA.2 variant in Shanghai. All asymptomatic patients and those with mild symptoms of Omicron infections were recruited from three major Fangcang shelter hospitals between March 26, 2022 and May 20, 2022. Nucleic acid for SARS-CoV-2 by real-time reverse-transcription polymerase chain reaction methods in nasopharyngeal swabs was assessed every day during the hospitalization. The value of cycle threshold lower than 35 was considered as positive result of SARS-CoV-2. A total of 214 592 cases were included in this study. The proportion of the asymptomatic patients was 76.90% and 23.10% of the recruited patients had mild symptoms. The median (interquartile range [IQR]: 25-75) duration of viral shedding (DVS) was 7 (5-10) days among all participants. The DVS varied greatly among different age groups. Children and the elderly had longer DVS compared with the adults. The booster shot of inactivated vaccine contributed to the shorter DVS in patients aged ≥70 years compared with the unvaccinated patients (8 [6-11] vs. 9 [6-12] days, p = 0.002]. Full inactivated vaccine regimen contributed to the shorter DVS in patients aged 3-6 years (7 [5-9] vs. 8 [5-10] days, p = 0.001]. In conclusion, the full inactivated vaccine regimen on children aged 3-6 years and booster inactivated vaccine regimen on the elderly aged ≥70 years appeared to be effective in reducing DVS. The booster vaccine regimen should be rigorously promoted and implemented.


Subject(s)
Asymptomatic Infections , COVID-19 , Adult , Child , Aged , Humans , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , COVID-19/prevention & control , SARS-CoV-2/genetics , China/epidemiology , Vaccination
2.
Zhonghua Yu Fang Yi Xue Za Zhi ; 57(5): 659-666, 2023 May 06.
Article in Chinese | MEDLINE | ID: covidwho-2323871

ABSTRACT

Objective: To estimate the latent period and incubation period of Omicron variant infections and analyze associated factors. Methods: From January 1 to June 30, 2022, 467 infections and 335 symptomatic infections in five local Omicron variant outbreaks in China were selected as the study subjects. The latent period and incubation period were estimated by using log-normal distribution and gamma distribution models, and the associated factors were analyzed by using the accelerated failure time model (AFT). Results: The median (Q1, Q3) age of 467 Omicron infections including 253 males (54.18%) was 26 (20, 39) years old. There were 132 asymptomatic infections (28.27%) and 335 (71.73%) symptomatic infections. The mean latent period of 467 Omicron infections was 2.65 (95%CI: 2.53-2.78) days, and 98% of infections were positive for nucleic acid test within 6.37 (95%CI: 5.86-6.82) days after infection. The mean incubation period of 335 symptomatic infections was 3.40 (95%CI: 3.25-3.57) days, and 97% of them developed clinical symptoms within 6.80 (95%CI: 6.34-7.22) days after infection. The results of the AFT model analysis showed that compared with the group aged 18-49 years old, the latent period [exp(ß)=1.36 (95%CI: 1.16-1.60), P<0.001] and incubation period [exp(ß)=1.24 (95%CI: 1.07-1.45), P=0.006] of infections aged 0-17 years old were prolonged. The latent period [exp(ß)=1.38 (95%CI: 1.17-1.63), P<0.001] and the incubation period [exp(ß)=1.26 (95%CI: 1.06-1.48), P=0.007] of infections aged 50 years old and above were also prolonged. Conclusion: The latent period and incubation period of most Omicron infections are within 7 days, and age may be a influencing factor of the latent period and incubation period.


Subject(s)
COVID-19 , Male , Humans , Adult , Adolescent , Young Adult , Middle Aged , Infant, Newborn , Infant , Child, Preschool , Child , SARS-CoV-2 , Infectious Disease Incubation Period , Asymptomatic Infections
3.
Zhonghua Wei Zhong Bing Ji Jiu Yi Xue ; 34(12): 1342-1344, 2022 12.
Article in Chinese | MEDLINE | ID: covidwho-2316787

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been infected rapidly and is generally susceptible to population. Moreover, it has become the most serious public health problem in the world. In the process of coronavirus disease 2019 (COVID-19) treatment, the traditional Chinese medicine (TCM) intervention has achieved positive efficacy and which is widely recognized. However, the COVID-19 epidemic is still very serious, especially due to the characteristics of asymptomatic infection such as concealment, limitations and subjective symptoms, which has increased the difficulty of prevention and control. In view of asymptomatic infection, isolation is the main management. There is little mention of specific treatment options in each version of COVID-19 treatment plan. Through systematic study of TCM theory, we explored the way of diagnosis and treatment of asymptomatic infections. Based on the theory of latent evil, clearing away latent pathogens to truncate the course of disease and reduce the incidence. Based on the theory of prevention of disease, strengthen the lung and stomach to protect the place from pathogen and prevent the transmission of disease evil. It is supplemented by accurate treatment according to individual, timing and local conditions, in order to provide reference for the treatment of asymptomatic infection.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Asymptomatic Infections , COVID-19 Drug Treatment , East Asian People , Medicine, Chinese Traditional
4.
J Math Biol ; 86(5): 82, 2023 04 25.
Article in English | MEDLINE | ID: covidwho-2312809

ABSTRACT

We formulate a general age-of-infection epidemic model with two pathways: the symptomatic infections and the asymptomatic infections. We then calculate the basic reproduction number [Formula: see text] and establish the final size relation. It is shown that the ratio of accumulated counts of symptomatic patients and asymptomatic patients is determined by the symptomatic ratio f which is defined as the probability of eventually becoming symptomatic after being infected. We also formulate and study a general age-of-infection model with disease deaths and with two infection pathways. The final size relation is investigated, and the upper and lower bounds for final epidemic size are given. Several numerical simulations are performed to verify the analytical results.


Subject(s)
Asymptomatic Infections , Epidemics , Humans , Asymptomatic Infections/epidemiology , Basic Reproduction Number , Probability , Models, Biological
5.
EBioMedicine ; 92: 104599, 2023 Jun.
Article in English | MEDLINE | ID: covidwho-2308362

ABSTRACT

BACKGROUND: The burden of COVID-19 in children and adolescents has increased during the delta and omicron waves, necessitating studies of long-term symptoms such as fatigue, dyspnoea and cognitive problems. Furthermore, immune responses in relation to persisting symptoms in younger people have not been well characterised. In this cohort study, we investigated the role of antibodies, vaccination and omicron reinfection upon persisting and long-term symptoms up to 8 months post-delta infection. METHODS: SARS-CoV-2 RT-PCR positive participants (n = 276, aged 10-20 years) were prospectively recruited in August 2021. We recorded the major symptoms of post COVID-19 condition and collected serum samples 3- and 8-months post delta infection. Binding antibodies were measured by spike IgG ELISA, and surrogate neutralising antibodies against Wuhan and delta variants by the hemagglutination test (HAT). FINDINGS: After delta infection, persisting symptoms at 3 months were significantly associated with higher delta antibody titres (OR 2.97, 95% CI 1.57-6.04, p = 0.001). Asymptomatic acute infection compared to symptomatic infection lowered the risk of persisting (OR 0.13, 95% CI 0.02-0.55, p = 0.013) and long-term (OR 0.28 95% CI 0.11-0.66, p = 0.005) symptoms at 3 and 8 months, respectively. Adolescents (16-20 years) were more likely to have long-term symptoms compared to children (10-15 years) (OR 2.44, 95% CI 1.37-4.41, p = 0.003). INTERPRETATION: This clinical and serological study compares long-term symptoms after delta infection between children and adolescents. The association between high antibody titres and persisting symptoms suggest the involvement of an immune mechanism. Similarly to adults, the dominant long-term symptoms in children are fatigue, dyspnoea and cognitive problems. FUNDING: This work was funded by the Ministry of Health and Care Services, Norway, the University of Bergen, Norway and Helse Vest, Norway (F-12621).


Subject(s)
COVID-19 , Hepatitis D , Adult , Humans , Adolescent , Child , Reinfection , Cohort Studies , SARS-CoV-2 , Antibodies , Asymptomatic Infections , Dyspnea , Fatigue
6.
Zhongguo Dang Dai Er Ke Za Zhi ; 25(1): 5-10, 2023 Jan 15.
Article in Chinese | MEDLINE | ID: covidwho-2306473

ABSTRACT

OBJECTIVES: To study the clinical features of children with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant infection. METHODS: A retrospective analysis was performed on the medical data of 201 children with coronavirus disease 2019 (COVID-19) who were hospitalized and diagnosed with SARS-CoV-2 Omicron variant infection in Quanzhou First Hospital from March 14 to April 7, 2022. Among the 201 children, there were 34 children with asymptomatic infection and 167 with symptomatic infection. The two groups were compared in terms of clinical features, results of experimental examinations, and outcome. RESULTS: Of all the 201 children, 161 (80.1%) had a history of exposure to COVID-19 patients and 132 (65.7%) had a history of COVID-19 vaccination. Among the 167 children with symptomatic infections, 151 had mild COVID-19 and 16 had common COVID-19, with no severe infection or death. Among the 101 children who underwent chest CT examination, 16 had ground glass changes and 20 had nodular or linear opacities. The mean time to nucleic acid clearance was (14±4) days for the 201 children with Omicron variant infection, and the symptomatic infection group had a significantly longer time than the asymptomatic infection group [(15±4) days vs (11±4) days, P<0.05]. The group vaccinated with one or two doses of COVID-19 vaccine had a significantly higher positive rate of IgG than the group without vaccination (P<0.05). The proportions of children with increased blood lymphocyte count in the symptomatic infection group was significantly lower than that in the asymptomatic infection group (P<0.05). Compared with the asymptomatic infection group, the symptomatic infection group had significantly higher proportions of children with increased interleukin-6, increased fibrinogen, and increased D-dimer (P<0.05). CONCLUSIONS: Most of the children with Omicron variant infection have clinical symptoms, which are generally mild. The children with symptomatic infection are often accompanied by decreased or normal blood lymphocyte count and increased levels of interleukin-6, fibrinogen, and D-dimer, with a relatively long time to nucleic acid clearance. Some of them had ground glass changes on chest CT.


Subject(s)
COVID-19 , Nucleic Acids , Child , Humans , Asymptomatic Infections , COVID-19/diagnosis , COVID-19/immunology , COVID-19/virology , COVID-19 Vaccines , Fibrinogen , Interleukin-6 , Retrospective Studies , SARS-CoV-2
7.
Nat Commun ; 14(1): 2235, 2023 04 19.
Article in English | MEDLINE | ID: covidwho-2295356

ABSTRACT

Reconstructing the incidence of SARS-CoV-2 infection is central to understanding the state of the pandemic. Seroprevalence studies are often used to assess cumulative infections as they can identify asymptomatic infection. Since July 2020, commercial laboratories have conducted nationwide serosurveys for the U.S. CDC. They employed three assays, with different sensitivities and specificities, potentially introducing biases in seroprevalence estimates. Using models, we show that accounting for assays explains some of the observed state-to-state variation in seroprevalence, and when integrating case and death surveillance data, we show that when using the Abbott assay, estimates of proportions infected can differ substantially from seroprevalence estimates. We also found that states with higher proportions infected (before or after vaccination) had lower vaccination coverages, a pattern corroborated using a separate dataset. Finally, to understand vaccination rates relative to the increase in cases, we estimated the proportions of the population that received a vaccine prior to infection.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , COVID-19/epidemiology , Seroepidemiologic Studies , Asymptomatic Infections , Biological Assay , Antibodies, Viral
8.
Viruses ; 15(4)2023 04 13.
Article in English | MEDLINE | ID: covidwho-2293664

ABSTRACT

BACKGROUND: The nucleocapsid protein of SARS-CoV-2 participates in viral replication, transcription, and assembly. Antibodies against this protein have been proposed for the epidemiological analysis of the seroprevalence of COVID-19 associated with natural infection by SARS-CoV-2. Health workers were one of the most exposed populations, and some had an asymptomatic form of the disease, so detecting IgG antibodies and subclasses against the N protein can help to reclassify their epidemiological status and obtain information about the effector mechanisms associated with viral elimination. METHODS: In this study, we analyzed 253 serum samples collected in 2021 and derived from health workers, and evaluated the presence of total IgG and subclasses against the N protein of SARS-CoV-2 by indirect ELISA. RESULTS: From the analyzed samples, 42.69% were positive to anti-N IgG antibodies. A correlation between COVID-19 asymptomatic infection and IgG antibodies was observed (p = 0.006). The detected subclasses were: IgG1 (82.4%), IgG2 (75.9%), IgG3 (42.6%), and IgG4 (72.6%). CONCLUSIONS: This work provides evidence about the high seroprevalence of total IgG and subclasses of anti-N and their relations with the asymptomatic infection of SARS-CoV-2 and related symptoms.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , COVID-19/epidemiology , Seroepidemiologic Studies , Asymptomatic Infections , Nucleocapsid , Immunoglobulin G , Antibodies, Viral
9.
Front Public Health ; 11: 1151038, 2023.
Article in English | MEDLINE | ID: covidwho-2305534

ABSTRACT

Background: In the early stage of COVID-19 epidemic, the Chinese mainland once effectively controlled the epidemic, but COVID-19 eventually spread faster and faster in the world. The purpose of this study is to clarify the differences in the epidemic data of COVID-19 in different areas and phases in Chinese mainland in 2020, and to analyze the possible factors affecting the occurrence and development of the epidemic. Methods: We divided the Chinese mainland into areas I, I and III, and divided the epidemic process into phases I to IV: limited cases, accelerated increase, decelerated increase and containment phases. We also combined phases II and III as outbreak phase. The epidemic data included the duration of different phases, the numbers of confirmed cases, asymptomatic infections, and the proportion of imported cases from abroad. Results: In area I, II and III, only area I has a Phase I, and the Phase II and III of area I are longer. In Phase IV, there is a 17-day case clearing period in area I, while that in area II and III are 2 and 0 days, respectively. In phase III or the whole outbreak phase, the average daily increase of confirmed cases in area I was higher than that in areas II and III (P = 0.009 and P = 0.001 in phase III; P = 0.034 and P = 0.002 in the whole outbreak phase), and the average daily in-hospital cases were most in area I and least in area III (P = 0.000, P = 0.000, and P = 0.000 in phase III; P = 0.000, P = 0.000, and P = 0.009 in the whole outbreak phase). The average number of daily in-hospital COVID-19 cases in phase III was more than that in phase II in each area (P = 0.000, P = 0.000, and P = 0.001). In phase IV, from March 18, 2020 to January 1, 2021, the increase of confirmed cases in area III was higher than areas I and II (both P = 0.000), and the imported cases from abroad in Chinese mainland accounted for more than 55-61%. From June 16 to July 2, 2020, the number of new asymptomatic infections in area III was higher than that in area II (P = 0.000), while there was zero in area I. From July 3, 2020 to January 1, 2021, the increased COVID-19 cases in area III were 3534, while only 14 and 0, respectively, in areas I and II. Conclusions: The worst epidemic areas in Chinese mainland before March 18, 2020 and after June 15, 2020 were area I and area III, respectively, and area III had become the main battlefield for Chinese mainland to fight against imported epidemic since March 18, 2020. In Wuhan, human COVID-19 infection might occur before December 8, 2019, while the outbreak might occur before January 16 or even 10, 2020. Insufficient understanding of COVID-19 hindered the implementation of early effective isolation measures, leading to COVID-19 outbreak in Wuhan, and strict isolation measures were effective in controlling the epidemic. The import of foreign COVID-19 cases has made it difficult to control the epidemic of area III. When humans are once again faced with potentially infectious new diseases, it is appropriate to first and foremost take strict quarantine measures as soon as possible, and mutual cooperation between regions should be explored to combat the epidemic.


Subject(s)
COVID-19 , Epidemics , SARS-CoV-2 , Humans , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19/transmission , Morbidity , Epidemics/prevention & control , Epidemics/statistics & numerical data , China/epidemiology , Disease Outbreaks/prevention & control , Disease Outbreaks/statistics & numerical data , Communicable Disease Control/methods
10.
Medicina (B Aires) ; 83(2): 185-189, 2023.
Article in English | MEDLINE | ID: covidwho-2302486

ABSTRACT

Asymptomatic infections with SARS-CoV-2 are associated with viral transmission and have a key role in the propagation of the pandemic. Understanding viral shedding during asymptomatic infections is critical. Unfortunately, data on asymptomatic SARS-CoV-2 infection in children is extremely limited. To determine the presence of viral viable shedding, we prospectively followed two healthy children of a family where both parents developed mild COVID-19 (April 2021). SARS-CoV-2 detection was made by RT-PCR and virus isolation by cell culture from saliva samples. Positive samples were sequenced to identify variants of SARS-CoV-2. Serum samples were evaluated to determine the presence of antibodies using a single enzyme-linked immunosorbent assay (ELISA, COVIDAR IgG). Both children were SARS-CoV-2 positive and asymptomatic. In addition, the virus grew in cell culture from saliva samples. Furthermore, one child showed viable SARS-CoV-2 for at least 17 days after the onset symptoms from his father. The recommended isolation period for asymptomatic contacts during the acquisition of data had been established for 10 days; however, this child remained with viable virus beyond that period. The positive samples from both children were consistent with B.1.1.28.1 lineage (Gamma). In both asymptomatic children, anti-Spike IgG was detected. Asymptomatic children may represent a source of infection that should not be underestimated during this pandemic.


Las infecciones asintomáticas por SARS-CoV-2 están asociadas a la transmisión viral y tienen un papel clave en la propagación de la pandemia. Comprender la excreción viral durante las infecciones asintomáticas es fundamental. Desafortunadamente, los datos sobre la infección asintomática por SARS-CoV-2 en niños son extremadamente limitados. Para determinar la presencia de excreción de virus viable, se siguió prospectivamente a dos niños sanos de una familia en la que ambos padres desarrollaron COVID-19 leve (abril 2021). La detección de SARS-CoV-2 se realizó por RT-PCR y el aislamiento del virus por cultivo celular a partir de muestras de saliva. Las muestras positivas se secuenciaron para identificar variantes de SARS-CoV-2. En las muestras de suero se determinó la presencia de anticuerpos utilizando un ensayo de ELISA (COVIDAR IgG). Ambos niños fueron positivos para SARS-CoV-2 y asintomáticos. Además, el virus creció en cultivos celulares a partir de muestras de saliva. Uno de los niños mantuvo SARS-CoV-2 viables durante al menos 17 días después de la aparición de los síntomas de su padre. El período de aislamiento recomendado para contactos asintomáticos durante la adquisición de datos se había establecido en 10 días, sin embargo, este niño permaneció con virus viable más allá de ese período. Las muestras positivas de estos niños correspondieron al linaje B.1.1.28.1 (Gamma). En ambos niños asintomáticos se detectó anticuerpos IgG anti-Spike. Concluimos que los niños asintomáticos pueden representar una fuente de infección que no debe subestimarse durante esta pandemia.


Subject(s)
COVID-19 , SARS-CoV-2 , Child , Humans , Asymptomatic Infections , Antibodies, Viral , Immunoglobulin G
11.
Swiss Med Wkly ; 151: w20487, 2021 04 26.
Article in English | MEDLINE | ID: covidwho-2261053

ABSTRACT

Relevant pandemic-spread scenario simulations can provide guiding principles for containment and mitigation policies. We devised a compartmental model to predict the effectiveness of different mitigation strategies with a main focus on mass testing. The model consists of a set of simple differential equations considering the population size, reported and unreported infections, reported and unreported recoveries, and the number of COVID-19-inflicted deaths. We assumed that COVID-19 survivors are immune (e.g., mutations are not considered) and that the virus is primarily passed on by asymptomatic and pre-symptomatic individuals. Moreover, the current version of the model does not account for age-dependent differences in the death rates, but considers higher mortality rates due to temporary shortage of intensive care units. The model parameters have been chosen in a plausible range based on information found in the literature, but it is easily adaptable, i.e., these values can be replaced by updated information any time. We compared infection rates, the total number of people getting infected and the number of deaths in different scenarios. Social distancing or mass testing can contain or drastically reduce the infections and the predicted number of deaths when compared with a situation without mitigation. We found that mass testing alone and subsequent isolation of detected cases can be an effective mitigation strategy, alone and in combination with social distancing. It is of high practical relevance that a relationship between testing frequency and the effective reproduction number of the virus can be provided. However, unless one assumes that the virus can be globally defeated by reducing the number of infected persons to zero, testing must be upheld, albeit at reduced intensity, to prevent subsequent waves of infection. The model suggests that testing strategies can be equally effective as social distancing, though at much lower economic costs. We discuss how our mathematical model may help to devise an optimal mix of mitigation strategies against the COVID-19 pandemic. Moreover, we quantify the theoretical limit of contact tracing and by how much the effect of testing is enhanced, if applied to sub-populations with increased exposure risk or prevalence.


Subject(s)
COVID-19/prevention & control , Models, Theoretical , Pandemics/prevention & control , Asymptomatic Infections , COVID-19/diagnosis , COVID-19/epidemiology , COVID-19 Testing , Humans , Mass Screening , Physical Distancing
12.
Clin Exp Immunol ; 209(3): 259-261, 2022 09 29.
Article in English | MEDLINE | ID: covidwho-2276438

ABSTRACT

During the last 2 years and a half, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide, causing about 6 million deaths. Clinical manifestations are highly variable, ranging from entirely asymptomatic infection to multiorgan failure and death. The outcome in immunocompromised patients is still a matter of debate, and so are the optimal strategies to prevent or treat the infection in these high-risk populations.


Subject(s)
COVID-19 , Asymptomatic Infections , COVID-19/prevention & control , Humans , SARS-CoV-2 , Vaccination
13.
JMIR Public Health Surveill ; 9: e43555, 2023 05 01.
Article in English | MEDLINE | ID: covidwho-2269839

ABSTRACT

BACKGROUND: SARS-CoV-2 rapid antigen testing (RAT) could be a useful supplementary test to diagnose larger numbers of acute asymptomatic infections and alleviate the limitations of polymerase chain reaction testing. However, hesitancy to undergo SARS-CoV-2 RAT may compromise its implementation. OBJECTIVE: We aimed to understand the prevalence and correlates of hesitancy to undergo RAT among adults not infected with SARS-CoV-2 in mainland China. METHODS: A nationwide cross-sectional survey on hesitancy to undergo SARS-CoV-2 RAT was conducted among adults not infected with SARS-CoV-2 in mainland China between April 29, 2022, and May 10, 2022. Participants completed an online questionnaire that covered the following COVID-19-related factors: sociodemographic characteristics, experiences of COVID-19 restrictions and knowledge of COVID-19, and attitude toward COVID-19 and its screening. This study was a secondary analysis of data from the survey. We compared the characteristics of participants by hesitancy to undergo SARS-CoV-2 RAT. Thereafter, logistic regression with a sparse group minimax concave penalty was used to identify correlates of hesitancy to undergo RAT. RESULTS: We recruited 8856 individuals with diverse demographic, socioeconomic, and geographic characteristics in China. Eventually, 5388 participants (valid response rate of 60.84%; 52.32% [2819/5388] women; median age 32 years) were included in the analysis. Among the 5388 participants, 687 (12.75%) expressed hesitancy to undergo RAT and 4701 (87.25%) were willing to undergo RAT. Notably, those who were from the central region (adjusted odds ratio [aOR] 1.815, 95% CI 1.441-2.278) and those who received COVID-19 information from traditional media (aOR 1.544, 95% CI 1.279-1.863) were significantly more likely to report hesitancy to undergo RAT (both P<.001). However, those who were women (aOR 0.720, 95% CI 0.599-0.864), were older (aOR 0.982, 95% CI 0.969-0.995), had postgraduate education (aOR 0.612, 95% CI 0.435-0.858), had children (<6 years old) and elders (>60 years old) in the family (aOR 0.685, 95% CI 0.510-0.911), had better knowledge about COVID-19 (aOR 0.942, 95% CI 0.916-0.970), and had mental health disorders (aOR 0.795, 95% CI 0.646-0.975) were less likely to report hesitancy to undergo RAT. CONCLUSIONS: Hesitancy to undergo SARS-CoV-2 RAT was low among individuals who were not yet infected with SARS-CoV-2. Efforts should be made to improve the awareness and acceptance of RAT among men, younger adults, individuals with a lower education or salary, families without children and elders, and individuals who access COVID-19 information via traditional media. In a reopening world, our study could inform the development of contextualized mass screening strategies in general and the scale-up of RAT in particular, which remains an indispensable option in emergency preparedness.


Subject(s)
COVID-19 , Female , Humans , Male , SARS-CoV-2 , Cross-Sectional Studies , China , Asymptomatic Infections
14.
Signal Transduct Target Ther ; 8(1): 123, 2023 03 15.
Article in English | MEDLINE | ID: covidwho-2277246

ABSTRACT

Persistent asymptomatic (PA) SARS-CoV-2 infections have been identified. The immune responses in these patients are unclear, and the development of effective treatments for these patients is needed. Here, we report a cohort of 23 PA cases carrying viral RNA for up to 191 days. PA cases displayed low levels of inflammatory and interferon response, weak antibody response, diminished circulating follicular helper T cells (cTfh), and inadequate specific CD4+ and CD8+ T-cell responses during infection, which is distinct from symptomatic infections and resembling impaired immune activation. Administration of a single dose of Ad5-nCoV vaccine to 10 of these PA cases elicited rapid and robust antibody responses as well as coordinated B-cell and cTfh responses, resulting in successful viral clearance. Vaccine-induced antibodies were able to neutralize various variants of concern and persisted for over 6 months, indicating long-term protection. Therefore, our study provides an insight into the immune status of PA infections and highlights vaccination as a potential treatment for prolonged SARS-CoV-2 infections.


Subject(s)
COVID-19 , Humans , SARS-CoV-2 , Asymptomatic Infections , Antibodies, Viral
15.
Lancet Microbe ; 4(4): e236-e246, 2023 04.
Article in English | MEDLINE | ID: covidwho-2287645

ABSTRACT

BACKGROUND: The efficacy of SARS-CoV-2 vaccines in preventing severe COVID-19 illness and death is uncertain due to the rarity of data in individual trials. How well the antibody concentrations can predict the efficacy is also uncertain. We aimed to assess the efficacy of these vaccines in preventing SARS-CoV-2 infections of different severities and the dose-response relationship between the antibody concentrations and efficacy. METHODS: We did a systematic review and meta-analysis of randomised controlled trials (RCTs). We searched PubMed, Embase, Scopus, Web of Science, Cochrane Library, WHO, bioRxiv, and medRxiv for papers published between Jan 1, 2020 and Sep 12, 2022. RCTs on the efficacy of SARS-CoV-2 vaccines were eligible. Risk of bias was assessed using the Cochrane tool. A frequentist, random-effects model was used to combine efficacy for common outcomes (ie, symptomatic and asymptomatic infections) and a Bayesian random-effects model was used for rare outcomes (ie, hospital admission, severe infection, and death). Potential sources of heterogeneity were investigated. The dose-response relationships of neutralising, spike-specific IgG and receptor binding domain-specific IgG antibody titres with efficacy in preventing SARS-CoV-2 symptomatic and severe infections were examined by meta-regression. This systematic review is registered with PROSPERO, CRD42021287238. FINDINGS: 28 RCTs (n=286 915 in vaccination groups and n=233 236 in placebo groups; median follow-up 1-6 months after last vaccination) across 32 publications were included in this review. The combined efficacy of full vaccination was 44·5% (95% CI 27·8-57·4) for preventing asymptomatic infections, 76·5% (69·8-81·7) for preventing symptomatic infections, 95·4% (95% credible interval 88·0-98·7) for preventing hospitalisation, 90·8% (85·5-95·1) for preventing severe infection, and 85·8% (68·7-94·6) for preventing death. There was heterogeneity in the efficacy of SARS-CoV-2 vaccines against asymptomatic and symptomatic infections but insufficient evidence to suggest whether the efficacy could differ according to the type of vaccine, age of the vaccinated individual, and between-dose interval (p>0·05 for all). Vaccine efficacy against symptomatic infection waned over time after full vaccination, with an average decrease of 13·6% (95% CI 5·5-22·3; p=0·0007) per month but can be enhanced by a booster. We found a significant non-linear relationship between each type of antibody and efficacy against symptomatic and severe infections (p<0·0001 for all), but there remained considerable heterogeneity in the efficacy, which cannot be explained by antibody concentrations. The risk of bias was low in most studies. INTERPRETATION: The efficacy of SARS-CoV-2 vaccines is higher for preventing severe infection and death than for preventing milder infection. Vaccine efficacy wanes over time but can be enhanced by a booster. Higher antibody titres are associated with higher estimates of efficacy but precise predictions are difficult due to large unexplained heterogeneity. These findings provide an important knowledge base for interpretation and application of future studies on these issues. FUNDING: Shenzhen Science and Technology Programs.


Subject(s)
COVID-19 Vaccines , COVID-19 , Humans , COVID-19 Vaccines/therapeutic use , Asymptomatic Infections , COVID-19/prevention & control , SARS-CoV-2 , Immunoglobulin G , Randomized Controlled Trials as Topic
16.
Front Public Health ; 11: 1107343, 2023.
Article in English | MEDLINE | ID: covidwho-2287561

ABSTRACT

Background: SARS-CoV-2 Omicron (BA.2) has stronger infectivity and more vaccine breakthrough capability than previous variants. Few studies have examined the impact of inactivated vaccines on the decrease of viral RNA levels in individuals with the Omicron variant, based on individuals' continuous daily cycle threshold (Ct) values and associated medical information from the infection to hospital discharge on a large population. Methods: We extracted 39,811 individuals from 174,371 Omicron-infected individuals according to data inclusion and exclusion criteria. We performed the survival data analysis and Generalized Estimating Equation to calculate the adjusted relative risk (aRR) to assess the effect of inactivated vaccines on the decrease of viral RNA levels. Results: Negative conversion was achieved in 54.7 and 94.3% of all infected individuals after one and 2 weeks, respectively. aRRs were shown weak effects on turning negative associated with vaccinations in asymptomatic infections and a little effect in mild diseases. Vaccinations had a protective effect on persistent positivity over 2 and 3 weeks. aRRs, attributed to full and booster vaccinations, were both around 0.7 and had no statistical significance in asymptomatic infections, but were both around 0.6 with statistical significance in mild diseases, respectively. Trends of viral RNA levels among vaccination groups were not significant in asymptomatic infections, but were significant between unvaccinated group and three vaccination groups in mild diseases. Conclusion: Inactivated vaccines accelerate the decrease of viral RNA levels in asymptomatic and mild Omicron-infected individuals. Vaccinated individuals have lower viral RNA levels, faster negative conversion, and fewer persisting positive proportions than unvaccinated individuals. The effects are more evident and significant in mild diseases than in asymptomatic infections.


Subject(s)
Asymptomatic Infections , COVID-19 , Humans , Vaccines, Inactivated , China/epidemiology , Retrospective Studies , SARS-CoV-2 , COVID-19/epidemiology , COVID-19/prevention & control , RNA, Viral
17.
Pediatr Infect Dis J ; 42(3): 232-239, 2023 03 01.
Article in English | MEDLINE | ID: covidwho-2285938

ABSTRACT

BACKGROUND: Asymptomatic SARS-CoV-2 infections have raised concerns for public health policies to manage epidemics. This systematic review and meta-analysis aimed to estimate the age-specific proportion of asymptomatic SARS-CoV-2 infected persons globally by year of age. METHODS: We searched PubMed, Embase, medRxiv and Google Scholar on September 10, 2020, and March 1, 2021. We included studies conducted during January to December 2020, before routine vaccination against COVID-19. Because we expected the relationship between the asymptomatic proportion and age to be nonlinear, multilevel mixed-effects logistic regression (QR decomposition) with a restricted cubic spline was used to model asymptomatic proportions as a function of age. RESULTS: A total of 38 studies were included in the meta-analysis. In total, 6556 of 14,850 cases were reported as asymptomatic. The overall estimate of the proportion of people who became infected with SARS-CoV-2 and remained asymptomatic throughout infection was 44.1% (6556/14,850, 95% CI: 43.3%-45.0%). The predicted asymptomatic proportion peaked in children (36.2%, 95% CI: 26.0%-46.5%) at 13.5 years, gradually decreased by age and was lowest at 90.5 years of age (8.1%, 95% CI: 3.4%-12.7%). CONCLUSIONS: Given the high rates of asymptomatic carriage in adolescents and young adults and their active role in virus transmission in the community, heightened vigilance and public health strategies are needed among these individuals to prevent disease transmission.


Subject(s)
COVID-19 , Epidemics , Child , Adolescent , Young Adult , Humans , COVID-19/epidemiology , SARS-CoV-2 , Public Health , Asymptomatic Infections/epidemiology
18.
Med Decis Making ; 43(4): 530-534, 2023 05.
Article in English | MEDLINE | ID: covidwho-2252506

ABSTRACT

BACKGROUND: It has been reported that a substantial number of COVID-19 infections are asymptomatic, with both symptomatic and asymptomatic infections contributing to transmission dynamics. Yet, the share of asymptomatic cases varies greatly across studies. One reason for this could be the measurement of symptoms in medical studies and surveys. DESIGN: In 2 experimental survey studies (total N > 3,000) with participants from Germany and the United Kingdom, respectively, we varied the inclusion of a filter question on whether participants who tested positive for COVID-19 had experienced symptoms prior to presenting a checklist of symptoms. We measured the reporting of asymptomatic (versus symptomatic) COVID-19 infections. RESULTS: The inclusion of a filter question increased the reporting of asymptomatic (versus symptomatic) COVID-19 infections. Particularly mild symptoms were underreported when using a filter question. CONCLUSIONS AND IMPLICATIONS: Filter questions affect the reporting of (a)symptomatic COVID-19 cases. To account for such differences in the estimation of population infection rates, future studies should transparently report the applied question format. HIGHLIGHTS: Both symptomatic and asymptomatic infections are important for COVID-19 transmission dynamics.In previous research, symptoms have been assessed either with or without a filter question prior to presenting a symptom list.We show that filter questions reduce the reporting of asymptomatic infections.Particularly mild symptoms are underreported when using a filter question.


Subject(s)
COVID-19 , Humans , COVID-19/epidemiology , SARS-CoV-2 , Asymptomatic Infections/epidemiology , Symptom Assessment , Prevalence
19.
J Correct Health Care ; 29(2): 143-149, 2023 04.
Article in English | MEDLINE | ID: covidwho-2265475

ABSTRACT

SARS-CoV-2 has spread quickly despite the implementation of various strategies to limit the spread of the disease. Current screening procedures are unable to detect asymptomatic infections. This study reports the prevalence of abnormal vital signs among incarcerated individuals with asymptomatic infections and proposes an enhanced screening algorithm that may detect asymptomatic infections. A case control study used a retrospective electronic chart review of COVID-19 infected people and matched controls housed in one Federal Bureau of Prisons institution. Data were collected on age, body mass index, medical history, temperature, blood oxygen saturation (SpO2), and symptoms. Fifty-seven laboratory-confirmed COVID-19 infections and 81 confirmed controls were identified. Asymptomatic infections were present in 35/57 people (61%) with a group minimum SpO2 94.4% (standard deviation [SD] 1.4) and a maximum oral temperature of 99.19°F (SD 0.36). An enhanced screening algorithm that uses pulse oximetry yields a sensitivity of 84.2%, 95% confidence interval [72.1-92.5]. Among asymptomatic people, there is a high prevalence of abnormal SpO2 and temperature measurements. A screening algorithm that uses both of these measures can detect asymptomatic infections with a low false positive rate.


Subject(s)
COVID-19 , Humans , COVID-19/diagnosis , Case-Control Studies , Retrospective Studies , Asymptomatic Infections/epidemiology , SARS-CoV-2 , Oximetry/methods
20.
Int J Infect Dis ; 130: 60-70, 2023 May.
Article in English | MEDLINE | ID: covidwho-2265428

ABSTRACT

OBJECTIVES: Asymptomatic infections and mild diseases were more common during the Omicron outbreak in Shanghai, China in 2022. This study aimed to assess the characteristics and viral RNA decay between patients with asymptomatic and mild infections. METHODS: A total of 55,111 patients infected with SARS-CoV-2 who were quarantined in the National Exhibition & Convention Center (Shanghai) Fangcang shelter hospital within 3 days after diagnosis from April 9 to May 23, 2022 were enrolled. The kinetics of cycle threshold (Ct) values of reverse transcription-polymerase chain reaction were assessed. The influencing factors for disease progression and the risk factors for the viral RNA shedding time (VST) were investigated. RESULTS: On admission, 79.6% (43,852/55,111) of the cases were diagnosed with asymptomatic infections, and 20.4% were mild diseases. However, 78.0% of initially asymptomatic subjects developed mild diseases at the follow-up. The final proportion of asymptomatic infections was 17.5%. The median time of symptom onset, the duration of symptoms, and the VST were 2 days, 5 days, and 7 days, respectively. Female, age 19-40 years, underlying comorbidities with hypertension and diabetes, and vaccination were associated with higher risks of progressing to mildly symptomatic infections. In addition, mildly symptomatic infections were found to be associated with prolonged VST compared with asymptomatic infections. However, the kinetics of viral RNA decay and dynamics of Ct values were similar among asymptomatic subjects, patients with asymptomatic-to-mild infection, and patients with mild infection. CONCLUSION: A large proportion of initially diagnosed asymptomatic Omicron infections is in the presymptomatic stage. The Omicron infection has a much shorter incubation period and VST than previous variants. The infectivity of asymptomatic infections and mildly symptomatic infections with Omicron is similar.


Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Female , Young Adult , Adult , SARS-CoV-2/genetics , COVID-19/diagnosis , COVID-19/epidemiology , RNA, Viral/genetics , Asymptomatic Infections/epidemiology , Retrospective Studies , Hospitals, Special , China/epidemiology , Mobile Health Units
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