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3.
PLoS One ; 16(12): e0261330, 2021.
Article in English | MEDLINE | ID: covidwho-1581751

ABSTRACT

Coronavirus disease 2019 (COVID-19) is an infectious disease of humans caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the first case was identified in China in December 2019 the disease has spread worldwide, leading to an ongoing pandemic. In this article, we present an agent-based model of COVID-19 in Luxembourg, and use it to estimate the impact, on cases and deaths, of interventions including testing, contact tracing, lockdown, curfew and vaccination. Our model is based on collation, with agents performing activities and moving between locations accordingly. The model is highly heterogeneous, featuring spatial clustering, over 2000 behavioural types and a 10 minute time resolution. The model is validated against COVID-19 clinical monitoring data collected in Luxembourg in 2020. Our model predicts far fewer cases and deaths than the equivalent equation-based SEIR model. In particular, with R0 = 2.45, the SEIR model infects 87% of the resident population while our agent-based model infects only around 23% of the resident population. Our simulations suggest that testing and contract tracing reduce cases substantially, but are less effective at reducing deaths. Lockdowns are very effective although costly, while the impact of an 11pm-6am curfew is relatively small. When vaccinating against a future outbreak, our results suggest that herd immunity can be achieved at relatively low coverage, with substantial levels of protection achieved with only 30% of the population fully immune. When vaccinating in the midst of an outbreak, the challenge is more difficult. In this context, we investigate the impact of vaccine efficacy, capacity, hesitancy and strategy. We conclude that, short of a permanent lockdown, vaccination is by far the most effective way to suppress and ultimately control the spread of COVID-19.


Subject(s)
COVID-19/epidemiology , Pandemics/prevention & control , Quarantine/statistics & numerical data , Vaccination/statistics & numerical data , Adolescent , Adult , Aged , Child , Child, Preschool , Contact Tracing/statistics & numerical data , Humans , Immunity, Herd , Infant , Infant, Newborn , Luxembourg/epidemiology , Masks/statistics & numerical data , Middle Aged , Young Adult
4.
Int Immunol ; 33(10): 507-513, 2021 09 25.
Article in English | MEDLINE | ID: covidwho-1575069

ABSTRACT

Understanding the precise nature and durability of protective immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential in order to gain insight into the pathophysiology of coronavirus disease 2019 (COVID-19) and to develop novel treatment strategies to this disease. Here, I succinctly summarize what is currently known and unknown about the immune response during COVID-19 and discuss whether natural infections can lead to herd immunity.


Subject(s)
COVID-19/immunology , Immunity, Herd/immunology , Immunity, Innate/immunology , Animals , Humans , SARS-CoV-2/immunology
6.
Vaccine ; 40(3): 403-405, 2022 01 24.
Article in English | MEDLINE | ID: covidwho-1569119

ABSTRACT

Mass COVID-19 vaccination, as the last resort to bring society to a new normal, has been rapidly rolled out in the US. However, because of the lifting of international travel restrictions, amid the many uncertainties induced by the emerging B.1.1.529 variant, it remains unclear about the timeline of reaching herd immunity and when our daily life will return to normalcy. Since access to a vaccine is an important predicate to the achievement of herd immunity, we articulate the vaccine access issue as the degree of fit between patients and the healthcare system in five dimensions: availability, accessibility, accommodation, affordability, and acceptability. These five dimensions can be adopted in existing health practice and policy to elucidate effective strategies for raising COVID-19 vaccination rates and improving vaccine equity in the fight against the new variant.


Subject(s)
COVID-19 , Vaccines , COVID-19 Vaccines , Humans , Immunity, Herd , SARS-CoV-2 , Vaccination
7.
J Med Virol ; 93(12): 6765-6777, 2021 Dec.
Article in English | MEDLINE | ID: covidwho-1544330

ABSTRACT

Avidity is defined as the binding strength of immunoglobulin G (IgG) toward its target epitope. Avidity is directly related to affinity, as both processes are determined by the best fit of IgG to epitopes. We confirm and extend data on incomplete avidity maturation of IgG toward severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein (NP), spike protein-1 (S1), and its receptor-binding domain (RBD) in coronavirus disease 2019 (COVID-19) patients. In SARS-CoV-2-infected individuals, an initial rise in avidity maturation was ending abruptly, leading to IgG of persistently low or intermediate avidity. Incomplete avidity maturation might facilitate secondary SARS-CoV-2 infections and thus prevent the establishment of herd immunity. Incomplete avidity maturation after infection with SARS-CoV-2 (with only 11.8% of cases showing finally IgG of high avidity, that is, an avidity index > 0.6) was contrasted by regular and rapid establishment of high avidity in SARS-CoV-2 naïve individuals after two vaccination steps with the BioNTech messenger RNA (mRNA) Vaccine (78% of cases with high avidity). One vaccination step was not sufficient for induction of complete avidity maturation in vaccinated SARS-CoV-2 naïve individuals, as it induced high avidity only in 2.9% of cases within 3 weeks. However, one vaccination step was sufficient to induce high avidity in individuals with previous SARS-CoV-2 infection.


Subject(s)
COVID-19/immunology , Immunoglobulin G/immunology , SARS-CoV-2/immunology , Antibodies, Viral/immunology , Antibody Formation/immunology , COVID-19/virology , COVID-19 Vaccines/immunology , Epitopes/immunology , Humans , Immunity, Herd/immunology , Immunologic Tests/methods , Spike Glycoprotein, Coronavirus/immunology , Vaccination/methods , Vaccines, Synthetic/immunology
8.
Front Public Health ; 9: 715931, 2021.
Article in English | MEDLINE | ID: covidwho-1526798

ABSTRACT

Widespread acceptance of COVID-19 vaccination is the next major step in fighting the pandemic. However, significant variations are observed in the willingness to take the vaccination by citizens across different countries. Arguably, differences in vaccination intentions will be influenced by beliefs around vaccines to influence health. Often perceptions of what others are doing and the information available guide individuals' behaviors for vaccination. This is more so in the digital age with the influence of the internet and media. This study aims to determine the factors that impact willingness to vaccinate for COVID-19. We examined factors associated with acceptance of vaccine based on (1) constructs of the Health Belief Model (HBM), (2) sources of information, (3) social media usage, (4) knowledge of COVID-19 treatment, and (5) perception of government's efforts for mitigation. Randomly sampled online survey data was collected by a global firm between December 2020 and January 2021 from 372 citizens (with a response rate of 96.6%) from multiple regions, including North America, the Middle East, Europe, and Asia. Ordered probit regression suggests that the health belief model constructs hold. Perceived severity of COVID-19 (P < 0.001) and action cues of others taking the vaccine positively influences a subject's vaccine intent (P < 0.001), perceived benefits and perceived efficacy of the vaccine positively influences a subject's vaccine intent (P < 0.001). Perceived barriers negatively influence vaccine intent (P < 0.001). Interestingly as for media usage, mainstream media (e.g., TV, newspaper) (P = 0.006) and social media (P = 0.013) both negatively influence a subject's vaccine intent. Social media platforms that are more entertainment and social-based, such as Whatsapp, Instagram, and YouTube, have a negative and significant influence on vaccine intent (P = 0.061), compared to other more information-based social media platforms (e.g., Twitter, LinkedIn). Knowledge of COVID-19 treatment positively influences vaccine intent (P = 0.023). Lastly, governmental efforts' perceived reliability in mitigation strategy (P = 0.028) and response efforts (P = 0.004) negatively influence vaccine intent. The study highlights the "wait-and-see" action cue from others and leaders in the community. It also informs the importance of shaping media information for vaccination through informative media and social media outlets to counteract any misinformation.


Subject(s)
COVID-19 , Social Media , Vaccines , COVID-19/drug therapy , COVID-19 Vaccines , Cross-Sectional Studies , Humans , Immunity, Herd , Reproducibility of Results , SARS-CoV-2 , Vaccination
9.
PLoS One ; 16(9): e0256889, 2021.
Article in English | MEDLINE | ID: covidwho-1523421

ABSTRACT

Vaccinating individuals with more exposure to others can be disproportionately effective, in theory, but identifying these individuals is difficult and has long prevented implementation of such strategies. Here, we propose how the technology underlying digital contact tracing could be harnessed to boost vaccine coverage among these individuals. In order to assess the impact of this "hot-spotting" proposal we model the spread of disease using percolation theory, a collection of analytical techniques from statistical physics. Furthermore, we introduce a novel measure which we call the efficiency, defined as the percentage decrease in the reproduction number per percentage of the population vaccinated. We find that optimal implementations of the proposal can achieve herd immunity with as little as half as many vaccine doses as a non-targeted strategy, and is attractive even for relatively low rates of app usage.


Subject(s)
COVID-19 Vaccines/administration & dosage , COVID-19/prevention & control , COVID-19/transmission , Contact Tracing/statistics & numerical data , Mass Vaccination/statistics & numerical data , COVID-19/immunology , Contact Tracing/instrumentation , Humans , Immunity, Herd , Mobile Applications , Models, Statistical , SARS-CoV-2/pathogenicity
10.
J Gen Virol ; 102(11)2021 11.
Article in English | MEDLINE | ID: covidwho-1522470

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread worldwide as a severe pandemic, and a significant portion of the infected population may remain asymptomatic. Given this, five surveys were carried out between May and September 2020 with a total of 3585 volunteers in the municipality of Foz do Iguaçu, State of Paraná, a triple border region between Brazil/Argentina/Paraguay. Five months after the first infection, volunteers were re-analysed for the production of IgG anti-Spike and anti-RBD-Spike, in addition to analyses of cellular immunity. Seroconversion rates ranged from 4.4 % to a peak of 37.21 % followed by a reduction in seroconversion to 21.1 % in September, indicating that 25 % of the population lost their circulating anti-SARS-CoV-2 antibodies 3 months after infection. Analyses after 5 months of infection showed that only 17.2 % of people still had anti-RBD-Spike antibodies, however, most volunteers had some degree of cellular immune response. The strategy of letting people become naturally infected with SARS-CoV-2 to achieve herd immunity is flawed, and the first contact with the virus may not generate enough immunogenic stimulus to prevent a possible second infection.


Subject(s)
COVID-19/immunology , Carrier State/immunology , Immunity, Herd , SARS-CoV-2/immunology , Antibodies, Viral/immunology , Argentina/epidemiology , Brazil/epidemiology , COVID-19/epidemiology , COVID-19/virology , Carrier State/epidemiology , Carrier State/virology , Humans , Immunity, Cellular , SARS-CoV-2/genetics , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/immunology
12.
PLoS One ; 16(10): e0258432, 2021.
Article in English | MEDLINE | ID: covidwho-1496509

ABSTRACT

Some people feel they are invincible to the novel coronavirus SARS-CoV-2 (COVID-19). They believe that being infected with COVID-19 would not be a serious threat to their health. While these people may or may not be correct in their personal risk assessment, we find that such perceived invincibility may undermine community efforts to achieve herd immunity. Multi-level analysis of survey respondents across 51 countries finds that perceived invincibility from COVID-19 is negatively associated with believing there is a need to prevent the spread of COVID-19 in one's community (n = 218,956) and one's willingness to inoculate against the disease (n = 71,148). These effects are most pronounced among individuals from countries lower in cultural collectivism (e.g., USA, UK, Canada) and highlight the need to consider the interplay of individual and cultural factors in our efforts to understand, predict, and promote preventative health behavior during a pandemic.


Subject(s)
COVID-19 , Pandemics , Vaccination , Health Behavior , Humans , Immunity, Herd , Surveys and Questionnaires
14.
Pan Afr Med J ; 39: 255, 2021.
Article in English | MEDLINE | ID: covidwho-1468748

ABSTRACT

In response to COVID-19 pandemic, the Zimbabwe government put in place various rigorous measures to curb the spread of the virus. Although roll-out and access to COVID-19 vaccines in Africa have been slow, the World Health Organization (WHO)-led COVID-19 Vaccines Global Access (COVAX) consortium and the African vaccine acquisition task team are striving to provide 720 million doses of COVID-19 vaccines to achieve 60% coverage in Africa by June, 2022. In line with this, the Zimbabwe vaccination programme commenced on the 26th February 2021 and as of 9th June 2021, approximately, 2.6% of the population have been fully vaccinated in the country. Although the COVID-19 pandemic has crippled the economy and caused significant strain on the public health system, much has been done in the country since the first case was recorded (20th March 2020). However, much more needs to be done to finally reach the expected 60% herd immunity by June 2022.


Subject(s)
COVID-19 Vaccines , COVID-19/prevention & control , Immunity, Herd , Pandemics/prevention & control , COVID-19/epidemiology , Humans , SARS-CoV-2 , Zimbabwe
15.
Epidemiol Health ; 43: e2021054, 2021.
Article in English | MEDLINE | ID: covidwho-1456422

ABSTRACT

Vaccination is considered to be the most effective measure for preventing the spread of coronavirus disease 2019 (COVID-19). Many countries, including of Korea, are focusing on achieving herd immunity with the goal of reaching a vaccination rate of 70-80%. However, achieving herd immunity does not mean eradicating COVID-19, and the following challenges can occur in the process of achieving herd immunity. First, as the vaccination rate is likely to slow down over time, it is necessary to promote the benefits of vaccination through risk communication strategies and provide incentives for those who have been vaccinated. Second, a booster dose may be required depending on future studies on vaccine-induced immunity. Third, since variants capable of evading immunity and with higher transmissibility can emerge, rapid contract tracing and regular community genomic surveillance could help mitigate the impact of new variants. When the impact of COVID-19 is controlled to the level of seasonal influenza, the current public health measures that have been strictly imposed on society since the beginning of the pandemic will no longer be needed. The overall response strategy to COVID-19 will need to change accordingly, based on evaluations of the level of population immunity. These changes will include more efficient and targeted contact tracing and eased quarantine measures for vaccinated close contacts and travelers. Mask wearing and a minimum of social distancing will still be required in the journey towards the end of the pandemic. The COVID-19 pandemic will end, but the virus will not disappear.


Subject(s)
COVID-19 Vaccines/administration & dosage , COVID-19/prevention & control , Immunity, Herd , Pandemics/prevention & control , Vaccination/statistics & numerical data , COVID-19/epidemiology , Contact Tracing , Humans , Quarantine , Republic of Korea/epidemiology
16.
J Korean Med Sci ; 36(38): e272, 2021 Oct 04.
Article in English | MEDLINE | ID: covidwho-1450797

ABSTRACT

The proportion of population vaccinated cannot be directly translated into the herd immunity. We have to account for the age-stratified contact patterns to calculate the population immunity level, since not every individual gathers evenly. Here, we calculated the contact-adjusted population immunity against severe acute respiratory syndrome coronavirus 2 in South Korea using age-specific incidence and vaccine uptake rate. We further explored options to achieve the theoretical herd immunity with age-varying immunity scenarios. As of June 21, 2021, when a quarter of the population received at least one dose of a coronavirus disease 2019 (COVID-19) vaccine, the contact-adjusted immunity level was 12.5% under the social distancing level 1. When 80% of individuals aged 10 years and over gained immunity, we could achieve a 58.2% contact-adjusted immunity level. The pros and cons of vaccinating children should be weighed since the risks of COVID-19 for the young are less than the elderly, and the long-term safety of vaccines is still obscure.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/immunology , Immunity, Herd/immunology , Mass Vaccination , SARS-CoV-2/immunology , COVID-19/prevention & control , Humans , Republic of Korea , Social Interaction
17.
Epidemiol Health ; 43: e2021071, 2021.
Article in English | MEDLINE | ID: covidwho-1450905

ABSTRACT

In Korea, where the successful control of the coronavirus disease 2019 (COVID-19) epidemic have been implemented by the follow-up survey management (containment) of COVID-19-infected persons, the number of infected persons has increased rapidly, and a re-epidemic trend is emerging. The Korean government is strengthening epidemic prevention activities, such as increasing the social distance in the metropolitan area to four levels and increasing the vaccination rate. The public has been complaining of dissatisfaction with the atrophy of socioeconomic activities and of distrust of epidemic prevention policies. Australia started with an incidence similar to that of Korea, but its social activities are more flexible than those of Korea, where the incidence is maintained at approximately 0.1 per 100,000 people. In comparing the differences between both countries in terms of the Oxford COVID-19 Government Response Tracker Stringency Index, it was found that Australia effectively regulates the number of infected cases by high-intensity intermittent mitigation and the subsequent allowance of social activities. Korea has also recommended a high-intensity intermittent mitigation policy as in Australia until community herd immunity via vaccination is formed.


Subject(s)
COVID-19 , Immunity, Herd , Disease Outbreaks/prevention & control , Humans , Public Health , SARS-CoV-2
18.
Indian J Public Health ; 65(3): 256-260, 2021.
Article in English | MEDLINE | ID: covidwho-1438804

ABSTRACT

Background: COVID-19 is a public health concern currently demanding continuous efforts to understand its epidemiology. Pimpri-Chinchwad township with a population of over 25 lakhs is located in Maharashtra, one of the worst affected states in India. After the incidence peaked in the township in mid-September 2020, cases started declining even as lockdown restrictions were eased. Objectives: A seroprevalence study was conducted to understand the transmission dynamics of the pandemic in this region. Methods: We carried out a population-based seroprevalence study for IgG antibodies for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) among 5000 residents 12 years and above selected by the cluster random sampling. We selected 50 clusters in slums, 80 clusters in tenements, and 70 clusters from housing societies. The field work for collection of samples was carried out from October 07 to October 17, 2020. We used kit from Abbott (SARS-CoV-2 IgG), which employs chemiluminescent microparticle immunoassay technology. The prevalence of IgG antibodies was expressed as point estimates with 95% confidence intervals (CIs). These were weighted for areas and cluster effect and further adjusted for test performance. Results: The overall seropositivity for IgG was 34.04% (95% CIl 31.3%-36.8%). Slum dwellers had 40.9% positivity rate (95% CI 37.0%-44.7%), those in tenements 41.2% (95% CI 37.7%-44.8%) and people living in housing societies had 29.8% positivity (95% CI 25.8%-33.8%). Conclusion: A considerable proportion of population had encountered the novel coronavirus approaching partial, if not complete, herd immunity, which may partly explain the declining trend in spite of easing of lockdown restrictions.


Subject(s)
Antibodies, Viral/blood , COVID-19/diagnosis , COVID-19/immunology , SARS-CoV-2 , Adolescent , Adult , Aged , COVID-19/epidemiology , Child , Communicable Disease Control , Humans , Immunity, Herd , Immunoglobulin G/blood , India/epidemiology , Middle Aged , Residence Characteristics , Seroepidemiologic Studies , Young Adult
19.
Vopr Virusol ; 66(4): 299-309, 2021 09 18.
Article in Russian | MEDLINE | ID: covidwho-1431288

ABSTRACT

AIM: To determine the level of SARS-CoV-2 seroprevalence among the Novosibirsk Region population against the background of the COVID-19 pandemic. MATERIAL AND METHODS: The work was carried out in 2 phases: 1) a cross-sectional cohort study performed 28.06- 15.07.2020; 2) longitudinal cohort 3-stage seromonitoring: 1st stage 28.06-15.07.2020; 2nd 14.09-04.10.2020; 3rd 10-30.12.2020 The work was carried out according to a unified methodology developed by Rospotrebnadzor with the participation of St-Petersburg Pasteur Institute, taking into account the recommendations of the WHO. IgG antibodies to the SARS-CoV-2 nucleocapsid protein were detected by ELISA using a kit of reagents produced by the SRCMSB (Obolensk) according to the manufacturer's instructions. Statistical analysis was performed using Microsoft Excel 2010 and other programs. RESULTS: The seroprevalence in the region's population was 9.1% (95% CI 8.0-10.2): maximum in children 14-17 years old (17.6%, 95% CI 12.3-23.9) and persons over 75 years (14.8%, 95% CI 11.4-18.8), minimum among persons 30-39 years old (4.9%, 95% CI 3.0-8.0). Increased rate was noted among the unemployed (15.4%, 95% CI 9.9-17.1) and other individuals (13.0%, 95% CI 8.6-18.5). Seroprevalence was 33.3% (95% CI 16.3-59.0) in COVID-19 convalescents and 19.0% (95% CI 13.9-25.0) in contact persons. More than 94.7% (95% CI 91.2-97.2) of seropositive individuals were asymptomatic. During the serological monitoring, seroprevalence increased from 7.4% (95% CI 6.2-8.9) at 1st stage 1 to 12.4% (95% CI 10.6-14.3) at 2nd , and 31% (95% CI 28.8-33.3) at 3rd stage. CONCLUSION: SARS-CoV-2 herd immunity has not reached the threshold level, this does not exclude exacerbation of the epidemic process.


Subject(s)
COVID-19/epidemiology , COVID-19/immunology , Immunity, Herd , Pandemics , SARS-CoV-2/immunology , Adolescent , Adult , Aged , Child , Female , Humans , Male , Middle Aged , Seroepidemiologic Studies , Siberia/epidemiology
20.
J Infect Dis ; 224(6): 931-933, 2021 09 17.
Article in English | MEDLINE | ID: covidwho-1426960
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