Humoral and cellular immunogenicity of homologous and heterologous booster vaccination in Ad26.COV2.S-primed individuals: Comparison by breakthrough infection.

Background: Whether or not a single-dose Ad26.COV2.S prime and boost vaccination induces sufficient immunity is unclear. Concerns about the increased risk of breakthrough infections in the Ad26.COV2.S-primed population have also been raised. Methods: A prospective cohort study was conducted. Participants included healthy adults who were Ad26.COV2.S primed and scheduled to receive a booster vaccination with BNT162b2, mRNA-1273, or Ad26.COV2.S. The IgG anti-receptor binding domain (RBD) antibody titers, neutralizing antibody (NAb) titers (against wild type [WT] and Omicron [BA.1 and BA.5]), and Spike-specific interferon-γ responses of the participants were estimated at baseline, 3-4 weeks, 3 months, and 6 months after booster vaccination. Results: A total of 89 participants were recruited (26 boosted with BNT162b2, 57 with mRNA-1273, and 7 with Ad26.COV2.S). The IgG anti-RBD antibody titers of all participants were significantly higher at 6 months post-vaccination than at baseline. The NAb titers against WT at 3 months post-vaccination were 359, 258, and 166 in the participants from the BNT162b2-, mRNA-1273-, and Ad26.COV2.S-boosted groups, respectively. Compared with those against WT, the NAb titers against BA.1/BA.5 were lower by 23.9/10.9-, 16.6/7.4-, and 13.8/7.2-fold in the participants from the BNT162b2-, mRNA-1273-, and Ad26.COV2.S-boosted groups, respectively, at 3 months post-vaccination. Notably, the NAb titers against BA.1 were not boosted after Ad26.COV2.S vaccination. Breakthrough infections occurred in 53.8%, 62.5%, and 42.9% of the participants from the BNT162b2-, mRNA-1273-, and Ad26.COV2.S-boosted groups, respectively. No significant difference in humoral and cellular immunity was found between individuals with and without SARS-CoV-2 breakthrough infections. Conclusion: Booster vaccination elicited acceptable humoral and cellular immune responses in Ad26.COV2.S-primed individuals. However, the neutralizing activities against Omicron subvariants were negligible, and breakthrough infection rates were remarkably high at 3 months post-booster vaccination, irrespective of the vaccine type. A booster dose of a vaccine containing the Omicron variant antigen would be required.

Comparison of culture-competent virus shedding duration of SARS-CoV-2 Omicron variant in regard to vaccination status: A prospective cohort study.

Previous studies have shown that fully vaccinated patients with SARS-CoV-2 Delta variants has shorter viable viral shedding period compared to unvaccinated or partially vaccinated patients. However, data about effects of vaccination against the viable viral shedding period in patients with SARS-CoV-2 Omicron variants were limited. We compared the viable viral shedding period of SARS-CoV-2 omicron variant regard to vaccination status. Saliva samples were obtained daily from patients with SARS-CoV-2 Omicron variant, and genomic assessments and virus culture was performed to those samples. We found no difference in viable viral shedding period between fully vaccinated and not or partially vaccinated, nor between 1st boostered vs non-boostered patients with SARS-CoV-2 Omicron variant.

Risk of transmission of COVID-19 from healthcare workers returning to work after a 5-day isolation, and kinetics of shedding of viable SARS-CoV-2 variant B.1.1.529 (Omicron).

OBJECTIVES: There have been limited data on the risk of onward transmission from individuals with Omicron variant infections who return to work after a 5-day isolation. We evaluated the risk of transmission from healthcare workers (HCWs) with Omicron variant who returned to work after a 5-day isolation and the viable virus shedding kinetics. METHODS: This investigation was performed in a tertiary care hospital, Seoul, South Korea. In a secondary transmission study, we retrospectively reviewed the data of HCWs confirmed as COVID-19 from March 14 to April 3, 2022 in units with 5 or more COVID-19-infected HCWs per week. In the viral shedding kinetics study, HCWs with Omicron variant infection who agreed with daily saliva sampling were enrolled between February and March, 2022. RESULTS: Of the 248 HCWs who were diagnosed with COVID-19 within 5 days of the return of an infected HCW, 18 (7%) had contact with the returned HCW within 1 to 5 days after their return. Of these, 9 (4%) had an epidemiologic link other than with the returning HCW, and 9 (4%) had contact with the returning HCW, without any other epidemiologic link. In the study of the kinetics of virus shedding (n=32), the median time from symptom onset to negative conversion of viable virus was 4 days (95% CI, 3 to 5 days). CONCLUSIONS: Our data suggest that the residual risk of virus transmission after 5 days of isolation following diagnosis or symptom onset is low.

Comparison of Secondary Attack Rate and Viable Virus Shedding between Patients with SARS-CoV-2 Delta and Omicron Variants: A Prospective Cohort Study.

BACKGROUNDS: There are limited data comparing the transmission rates and kinetics of viable virus shedding of the Omicron variant to those of the Delta variant. We compared these rates in hospitalized patients infected with Delta and Omicron variants. METHODS: We prospectively enrolled adult patients with COVID-19 admitted to a tertiary care hospital in South Korea between September 2021 and May 2022. Secondary attack rates were calculated by epidemiologic investigation, and daily saliva samples were collected to evaluate viral shedding kinetics. Genomic and subgenomic SARS-CoV-2 RNA was measured by PCR, and virus culture was performed from daily saliva samples. RESULTS: A total of 88 patients with COVID-19 who agreed to daily sampling and were interviewed, were included. Of the 88 patients, 48 (59%) were infected with Delta, and 34 (41%) with Omicron; a further five patients gave undetectable or inconclusive RNA PCR results and one was suspected of being co-infected with both variants. Omicron group had a higher secondary attack rate (31% [38/124]) versus 7% [34/456], p<0.001). Survival analysis revealed that shorter viable virus shedding period was observed in Omicron variant compared with Delta variant (median 4 days, IQR [1 -7], vs. 8.5 days, IQR [5 - 12 days], p<0.001). Multivariable analysis revealed that moderate-to-critical disease severity (HR 1.96), and immunocompromised status (HR 2.17) were independent predictors of prolonged viral shedding, whereas completion of initial vaccine series or 1st booster-vaccinated status (HR 0.49), and Omicron infection (HR 0.44) were independently associated with shorter viable virus shedding. CONCLUSION: Patients with Omicron infections had higher transmission rates but shorter periods of transmissible virus shedding than those with Delta infections. This article is protected by copyright. All rights reserved.

Clinical scoring system to predict viable viral shedding in patients with COVID-19.

BACKGROUND: The Centers for Disease Control and Prevention (CDC) recommends 5-10 days of isolation for patients with COVID-19, depending on symptom duration and severity. However, in clinical practice, an individualized approach is required. We thus developed a clinical scoring system to predict viable viral shedding. METHODS: We prospectively enrolled adult patients with SARS-CoV-2 infection admitted to a hospital or community isolation facility between February 2020 and January 2022. Daily dense respiratory samples were obtained, and genomic RNA viral load assessment and viral culture were performed. Clinical predictors of negative viral culture results were identified using survival analysis and multivariable analysis. RESULTS: Among 612 samples from 121 patients including 11 immunocompromised patients (5 organ transplant recipients, 5 with hematologic malignancy, and 1 receiving immunosuppressive agents) with varying severity, 154 (25%) revealed positive viral culture results. Multivariable analysis identified symptom onset day, viral copy number, disease severity, organ transplant recipient, and vaccination status as independent predictors of culture-negative rate. We developed a 4-factor predictive model based on viral copy number (-3 to 3 points), disease severity (1 point for moderate to critical disease), organ transplant recipient (2 points), and vaccination status (-2 points for fully vaccinated). Predicted culture-negative rates were calculated through the symptom onset day and the score of the day the sample was collected. CONCLUSIONS: Our clinical scoring system can provide the objective probability of a culture-negative state in a patient with COVID-19 and is potentially useful for implementing personalized de-isolation policies beyond the simple symptom-based isolation strategy.

Daily, self-test rapid antigen test to assess SARS-CoV-2 viability in de-isolation of patients with COVID-19.

Background: Isolation of COVID-19 patients is a crucial infection control measure to prevent further SARS-CoV-2 transmission, but determining an appropriate timing to end the COVID-19 isolation is a challenging. We evaluated the performance of the self-test rapid antigen test (RAT) as a potential proxy to terminate the isolation of COVID-19 patients. Materials and methods: Symptomatic COVID-19 patients were enrolled who were admitted to a regional community treatment center (CTC) in Seoul (South Korea). Self-test RAT and the collection of saliva samples were performed by the patients, on a daily basis, until patient discharge. Cell culture and subgenomic RNA detection were performed on saliva samples. Results: A total of 138 pairs of saliva samples and corresponding RAT results were collected from 34 COVID-19 patients. Positivity of RAT and cell culture was 27% (37/138) and 12% (16/138), respectively. Of the 16 culture-positive saliva samples, seven (43.8%) corresponding RAT results were positive. Using cell culture as the reference standard, the overall percent agreement, percent positive agreement, and percent negative agreement of RAT were 71% (95% CI, 63-78), 26% (95% CI, 12-42), and 82% (95% CI, 76-87), respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of the RAT for predicting culture results were 44% (95% CI, 20-70), 75% (95% CI, 66-82), 18% (95% CI, 8-34), and 91% (95% CI, 84-96), respectively. Conclusion: About half of the patients who were SARS-CoV-2 positive based upon cell culture results gave negative RAT results. However, the remaining positive culture cases were detected by RAT, and RAT showed relatively high negative predictive value for viable viral shedding.

Evaluation of In-Hospital Cluster of COVID-19 Associated With a Patient With Prolonged Viral Shedding Using Whole-Genome Sequencing.

BACKGROUND: Patients with hematologic malignancies may produce replication-competent virus beyond 20 days of SARS-CoV-2 infection. However, data regarding the transmission of SARS-CoV-2 from patients with prolonged viral shedding is limited. METHODS: In May 2022, four additional cases of COVID-19 were reported in a hematologic ward at a tertiary care hospital in South Korea, after an 8-week isolation of a patient with prolonged viral shedding. We performed whole-genome sequencing (WGS) of SARS-CoV-2 to evaluate the possibility of post-isolation transmission from this prolonged viral shedding. RESULTS: A patient (case 1) with acute myeloid leukemia was released from isolation 54 days after the diagnosis of COVID-19 based on rising Ct value of up to 29.3, and moved to a six-patient room. On days 10 and 11 post-isolation, his doctor (case 2) and 2 patients who were his roommates (case 3, 4) had positive SARS-CoV-2 PCR results. Additionally, 16 days post-isolation, another patient (case 5) in a remote room had positive SARS-CoV-2 PCR result. All the three patients were hospitalized for ≥ 14 days when they were diagnosed with SARS-CoV-2 infection. Except for case 3, the remaining 4 cases were available for WGS, which revealed that case 1 exhibited a 7 nucleotides difference in comparison to cases 4 and 5 and case 2 displayed a 20 nucleotides difference compared with case 1, while sequences of cases 4 and 5 were identical. CONCLUSIONS: Despite the possibility of transmission from the patient with prolonged viral shedding, no evidence of the transmission of SARS-CoV-2 from the patient with prolonged positive RT-PCR using WGS was found.

Kinetics of neutralizing antibodies against SARS-CoV-2 infection according to sex, age, and disease severity.

Knowledge of the factors affecting the difference in kinetics and longevity of the neutralizing antibody (nAb) response to SARS-CoV-2 is necessary to properly prioritize vaccination. In the present study, from March to December 2020, of the 143 patients who recovered from COVID-19, 87 underwent study visits scheduled every 3 months. Patient demographics and blood samples were collected followed by a plaque reduction neutralization test to analyze nAb titers. A linear mixed model was used to compare the effects of sex, age, and disease severity over time. Results demonstrated a gradual reduction in nAb titers over time with a significant decrease from 6 to 9 months post-COVID-19 infection (p < 0.001). In time-to-sex, age, and disease severity comparisons, reduction in nAb titers over time was unaffected by sex (p = 0.167), age (p = 0.188), or disease severity (p = 0.081). Additionally, the nAb titer was 1.46 times significantly higher in those aged ≥ 50 years than in those aged < 50 years (p = 0.036) irrespective of time Moreover, the nAb titer was 2.41 times higher in the moderate or above than that in the below moderate disease severity group (p < 0.001). However, no significant differences were observed in terms of sex (p = 0.300). Given the reduction in nAbs over time, maintaining protective neutralizing antibodies regardless of sex, age, or disease severity is needed.

Clinical scoring system to predict viable viral shedding in patients with COVID-19

Background : The Centers for Disease Control and Prevention (CDC) recommends 5–10 days of isolation for patients with COVID-19, depending on symptom duration and severity. However, in clinical practice, an individualized approach is required. We thus developed a clinical scoring system to predict viable viral shedding. Methods : We prospectively enrolled adult patients with SARS-CoV-2 infection admitted to a hospital or community isolation facility between February 2020 and January 2022. Daily dense respiratory samples were obtained, and genomic RNA viral load assessment and viral culture were performed. Clinical predictors of negative viral culture results were identified using survival analysis and multivariable analysis. Results : Among 612 samples from 121 patients including 11 immunocompromised patients (5 organ transplant recipients, 5 with hematologic malignancy, and 1 receiving immunosuppressive agents) with varying severity, 154 (25%) revealed positive viral culture results. Multivariable analysis identified symptom onset day, viral copy number, disease severity, organ transplant recipient, and vaccination status as independent predictors of culture-negative rate. We developed a 4-factor predictive model based on viral copy number (-3 to 3 points), disease severity (1 point for moderate to critical disease), organ transplant recipient (2 points), and vaccination status (-2 points for fully vaccinated). Predicted culture-negative rates were calculated through the symptom onset day and the score of the day the sample was collected. Conclusions : Our clinical scoring system can provide the objective probability of a culture-negative state in a patient with COVID-19 and is potentially useful for implementing personalized de-isolation policies beyond the simple symptom-based isolation strategy.

Clinical Application of a Solid-Phase Assay for SARS-CoV-2 IgG to Predict a Neutralizing Antibody Titer.

BACKGROUND: To assess protective immunity among a general population against severe acute respiratory syndrome coronavirus 2, the correlation of the commercially available solid-phase assay (SPA) for SARS-CoV-2 IgG with a neutralization assay must be investigated. METHODS: Both the neutralization assay and SPA were performed on samples of 143 recovered coronavirus disease 2019 (COVID-19) patients. SARS-CoV-2 IgG was measured using two SPAs for the chemiluminescence immunoassay principle with different target proteins: nucleocapsid and spike protein (Architect i2000SR [Abbott] and Liaison XL [DiaSorin], respectively). The plaque reduction neutralization test (PRNT) was conducted to obtain titers for the neutralizing antibody. RESULTS: All patients had PRNT titers ranging from 10 to 2,560. Spike Ab SPA had greater sensitivity than nucleocapsid Ab SPA (81.1% [116/143] and 70.6% [101/143], respectively, p = 0.003). The values measured for both SPAs had a positive correlation with the PRNT titers (both R = 0.77, p < 0.001). To predict a high PRNT titer (≥ 160), cutoff values of two SPAs were adjusted based on receiver-operating characteristics curve analysis. The nucleocapsid Ab SPA (cutoff index of 4.17) attained 90.3% sensitivity and 75.9% specificity, whereas the spike Ab SPA (cutoff value of 109 unit/mL) attained 87.1% sensitivity and 89.3% specificity. Therefore, the spike Ab SPA had greater specificity than the nucleocapsid Ab SPA (p = 0.003). CONCLUSIONS: The qualitative SPA for nucleocapsid Ab, as well as the quantitative SPA for spike Ab, had a modest positive correlation with the neutralization assay. However, spike Ab SPA was more suitable for neutralizing capacity.

The molecular epidemiology of multiple zoonotic origins of SARS-CoV-2.

Understanding the circumstances that lead to pandemics is important for their prevention. We analyzed the genomic diversity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) early in the coronavirus disease 2019 (COVID-19) pandemic. We show that SARS-CoV-2 genomic diversity before February 2020 likely comprised only two distinct viral lineages, denoted "A" and "B." Phylodynamic rooting methods, coupled with epidemic simulations, reveal that these lineages were the result of at least two separate cross-species transmission events into humans. The first zoonotic transmission likely involved lineage B viruses around 18 November 2019 (23 October to 8 December), and the separate introduction of lineage A likely occurred within weeks of this event. These findings indicate that it is unlikely that SARS-CoV-2 circulated widely in humans before November 2019 and define the narrow window between when SARS-CoV-2 first jumped into humans and when the first cases of COVID-19 were reported. As with other coronaviruses, SARS-CoV-2 emergence likely resulted from multiple zoonotic events.

Transmission and Infectious SARS-CoV-2 Shedding Kinetics in Vaccinated and Unvaccinated Individuals.

Importance: Data are limited on whether patients with breakthrough COVID-19 infection have the potential to significantly contribute to the spread of SARS-CoV-2. Objective: To compare the secondary attack rate and infectious viral shedding kinetics of SARS-CoV-2 between fully vaccinated individuals (breakthrough infection group) and partially or unvaccinated individuals (nonbreakthrough infection group). Design, Setting, and Participants: This cohort study assessed secondary transmission by analyzing the epidemiologic data of health care workers, inpatients, and caregivers diagnosed with COVID-19 during hospitalization or residence in a tertiary care hospital between March 1, 2020, and November 6, 2021. To evaluate viral shedding kinetics, the genomic RNA of SARS-CoV-2 was measured using polymerase chain reaction and performed virus culture from daily saliva samples of individuals with mild COVID-19 infected with the Delta variant who were isolated in a community facility in Seoul, South Korea, between July 20 and August 20, 2021. Exposures: COVID-19 vaccination. Main Outcomes and Measures: The secondary attack rate and infectious viral shedding kinetics according to COVID-19 vaccination status. Results: A total of 173 individuals (median [IQR] age, 47 [32-59] years; 100 female [58%]) with COVID-19 were included in the secondary transmission study, of whom 50 (29%) had a breakthrough infection. Secondary transmission was significantly less common in the breakthrough infection group than in the nonbreakthrough infection group (3 of 43 [7%] vs 29 of 110 [26%]; P = .008). In the viral shedding kinetics study, 45 patients (median age, 37 years [IQR, 25-49 years]; 14 female [31%]) infected with the Delta variant were included, of whom 6 (13%) were fully vaccinated and 39 (87%) were partially or unvaccinated. Although the initial genomic viral load was comparable between the 2 groups, viable virus in cell culture was detected for a notably longer duration in partially vaccinated (8 days after symptom onset) or unvaccinated (10 days after symptom onset) individuals compared with fully vaccinated individuals (4 days after symptom onset). Conclusions and Relevance: In this cohort study, although the initial genomic viral load was similar between vaccinated and unvaccinated individuals, fully vaccinated individuals had a shorter duration of viable viral shedding and a lower secondary attack rate than partially vaccinated or unvaccinated individuals. Data from this study provide important evidence that despite the possibility of breakthrough infections, COVID-19 vaccinations remain critically useful for controlling the spread of SARS-CoV-2.

Clinical and Virological Characteristics of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) B.1.617.2 (Delta) Variant: A Prospective Cohort Study.

BACKGROUND: Data on the clinical and virological characteristics of the Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are limited. This prospective cohort study compared the characteristics of the Delta variant to other variants. METHODS: Adult patients with mild coronavirus disease 2019 (COVID-19) who agreed to daily saliva sampling at a community isolation facility in South Korea between July and August 2021 were enrolled. Scores of 28 COVID-19-related symptoms were recorded daily. The genomic RNA and subgenomic RNA from saliva samples were measured by real-time reverse-transcription polymerase chain reaction (PCR). Cell cultures were performed on saliva samples with positive genomic RNA results. RESULTS: A total of 141 patients (Delta group, n = 108 [77%]; non-Delta group, n = 33 [23%]) were enrolled. Myalgia was more common in the Delta group than in the non-Delta group (52% vs 27%, P = .03). Total symptom scores were significantly higher in the Delta group between days 3 and 10 after symptom onset. Initial genomic RNA titers were similar between the 2 groups; however, during the late course of disease, genomic RNA titers were higher in the Delta group. Negative conversion of subgenomic RNA was slower in the Delta group (median 9 vs 5 days; P < .001). The duration of viral shedding in terms of positive viral culture was also longer in the Delta group (median 5 vs 3 days; P = .002). CONCLUSIONS: COVID-19 patients infected with the Delta variant exhibited prolonged viable viral shedding with more severe symptoms than those infected with non-Delta variants.

Nosocomial Outbreak by Delta Variant From a Fully Vaccinated Patient.

BACKGROUND: The potential for a nosocomial outbreak of coronavirus disease 2019 (COVID-19) from a fully vaccinated individual is largely unknown. METHODS: In October 2021, during the time when the delta variant was dominant, a nosocomial outbreak of COVID-19 occurred in two wards in a tertiary care hospital in Seoul, Korea. We performed airflow investigations and whole-genome sequencing (WGS) of the virus. RESULTS: The index patient developed symptoms 1 day after admission, and was diagnosed with COVID-19 on day 4 post-admission. He was fully vaccinated (ChAdOx1 nCoV-19) 2 months before the diagnosis. Three inpatients and a caregiver in the same room, two inpatients in an adjacent room, two inpatients in rooms remote from the index room, and one nurse on the ward tested positive. Also, two resident doctors who stayed in an on-call room located on the same ward tested positive (although they had no close contact), as well as a caregiver who stayed on an adjacent ward, and a healthcare worker who had casual contact with this caregiver. Samples from five individuals were available for WGS, and all showed ≤ 1 single-nucleotide polymorphism difference. CCTV footage showed that the index case walked frequently in the corridors of two wards. An airflow study showed that the air from the corridor flowed into the resident on-call room, driven by an air circulator that was always turned on. CONCLUSION: Transmission of severe acute respiratory syndrome coronavirus 2 from a fully vaccinated index occurred rapidly via the wards and on-call room. Care must be taken to not use equipment that can change the airflow.

Insights into the immune responses of SARS-CoV-2 in relation to COVID-19 vaccines.

The three types of approved coronavirus disease 2019 (COVID-19) vaccines that have been emergency-use listed (EUL) by the World Health Organization are mRNA vaccines, adenovirus-vectored vaccines, and inactivated vaccines. Canonical vaccine developments usually take years or decades to be completed to commercialization; however, the EUL vaccines being used in the current situation comprise several COVID-19 vaccine candidates applied in studies and clinical settings across the world. The extraordinary circumstances of the COVID-19 pandemic have necessitated the emergency authorization of these EUL vaccines, which have been rapidly developed. Although the benefits of the EUL vaccines outweigh their adverse effects, there have been reports of rare but fatal cases directly associated with COVID-19 vaccinations. Thus, a reassessment of the immunological rationale underlying EUL vaccines in relation to COVID-19 caused by SARSCOV-2 virus infection is now required. In this review, we discuss the manifestations of COVID-19, immunologically projected effects of EUL vaccines, reported immune responses, informed issues related to COVID-19 vaccination, and the potential strategies for future vaccine use against antigenic variants.

COVID-19 Cluster Linked to Aerosol Transmission of SARS-CoV-2 via Floor Drains.

BACKGROUND: Recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission through exposure to aerosols has been suggested. Therefore, we investigated the possibility of aerosol SARS-CoV-2 transmission within an apartment complex where residents reported testing positive for SARS-CoV-2 despite having no direct contact with other SARS-CoV-2-infected people. METHODS: Information on symptom onset and exposure history of the patients was collected by global positioning system (GPS) tracking to investigate possible points of contact or spread. Samples collected from patients and from various areas of the complex were analyzed using RNA sequencing. Phylogenetic analysis was also performed. RESULTS: Of 19 people with confirmed SARS-CoV-2 infection, 5 reported no direct contact with other residents and were from apartments in the same vertical line. Eight environmental samples tested positive for the virus. Phylogenetic analyses revealed that 3 of the positive cases and 1 environmental sample belonged to the B.1.497 lineage. Additionally, 3 clinical specimens and 1 environmental sample from each floor of the complex had the same amino acid substitution in the ORF1ab region. CONCLUSIONS: SARS-CoV-2 transmission possibly occurs between different floors of an apartment building through aerosol transmission via nonfunctioning drain traps.

Dynamics of Viral Shedding and Symptoms in Patients with Asymptomatic or Mild COVID-19.

We conducted a prospective cohort study at a community facility designated for the isolation of individuals with asymptomatic or mild COVID-19 between 10 January and 22 February 2021 to investigate the relationship of viral shedding with symptom changes of COVID-19. In total, 89 COVID-19 adult patients (12 asymptomatic, 16 presymptomatic, 61 symptomatic) were enrolled. Symptom scores, the genomic RNA and subgenomic RNA of SARS-CoV-2 from saliva samples with a cell culture were measured. Asymptomatic COVID-19 patients had a similar viral load to symptomatic patients during the early course of the disease, but exhibited a rapid decrease in viral load with the loss of infectivity. Subgenomic RNA and viable virus by cell culture in asymptomatic patients were detected only until 3 days after diagnosis, and the positivity of the subgenomic RNA and cell culture in symptomatic patients gradually decreased in both from 40% in the early disease course to 13% at 10 days and 4% at 8 days after the symptom onset, respectively. In conclusion, symptomatic patients have a high infectivity with high symptom scores during the early disease course and gradually lose infectivity depending on the symptom. Conversely, asymptomatic patients exhibit a rapid decrease in viral load with the loss of infectivity, despite a similar viral load during the early disease course.