Viral and antibody dynamics of acute infection with SARS-CoV-2 omicron variant (B.1.1.529): a prospective cohort study from Shenzhen, China

Elucidating viral dynamics within the host is important for designing public health measures against SARS-CoV-2, particularly during the early stages of infection when transmission potential rapidly increases. We aimed to analyse the viral and antibody dynamics of the omicron variant in relation to symptom onset or laboratory confirmation and replication dynamics throughout the infection course.In this prospective cohort study, patients with laboratory-confirmed SARS-CoV-2 infection who were admitted to Shenzhen Third People's Hospital (Shenzhen, China) between Jan 11, 2020, and April 24, 2022, were screened for eligibility. We included immunocompetent individuals with acute SARS-CoV-2 infection without antiviral agents targeting SARS-CoV-2. Serial nasopharyngeal swabs and plasma samples were analysed for viral RNAs and specific IgG antibodies of SARS-CoV-2. The comparative viral and antibody kinetics in association with symptom onset or laboratory confirmation and replication dynamics throughout the infection course were calculated by the locally estimated scatterplot smoothing curve fitting polynomial regression. The associations between viral and antibody dynamics and vaccination, age, sex, disease severity, and underlying health conditions were analysed using the Mann-Whitney U test and the Gehan-Breslow-Wilcoxon method.15 406 serial nasopharyngeal swabs and 2324 plasma samples were taken from 2043 individuals with acute SARS-CoV-2 infection (n=217 prototype [A.1] and D614G [B.1] variant [wild-type]; n=105 delta variant [B.1.617.2]; n=1721 omicron variant [B.1.1.529]) and were included for the analyses. The mean Ct value of omicron variant on the first day post symptom onset (dpo; defined as the first day post laboratory confirmation in asymptomatic participants) was 22·65 (95% CI 22·05-23·26). Peak viral load was reached with a mean Ct value of 17·63 (17·47-17·79) at a mean of 3·19 dpo (95% CI 3·09-3·28), and viral clearance (Ct values ≥35) was reached at a mean of 13·50 dpo (95% CI 13·32-13·67). Omicron variant showed faster viral replication and clearance than wild-type SARS-CoV-2 and delta variant, and the viral load at the first dpo and the peak viral load was lower than delta variant but higher than wild-type SARS-CoV-2. Age, sex, disease severity, and underlying health conditions were associated with the viral dynamics of omicron variant, with faster viral clearance found in young (aged 0-14 years), male, and asymptomatic participants, and those without underlying health conditions. Replication dynamics thoughout the infection course showed that peak viral load was reached at a mean of 5·06 dpo (4·76-5·36) and viral clearance took a mean of 14·27 days (13·6-14·93) for omicron variant. SARS-CoV-2-specific IgG increased earlier and faster to significantly higher concentrations in breakthrough infection than naive infection with omicron variant, despite long intervals (≥7 months) between the last dose of vaccination and infection.Our data provide a comprehensive overview of the longitudinal viral and antibody dynamics of omicron variant in people with acute SARS-CoV-2 infection, with important implications for public health strategies, including population screening, antiviral treatment, isolation periods, and vaccination.National Natural Science Foundation of China and Emergency Key Program of Guangzhou Laboratory.For the Chinese translation of the abstract see Supplementary Materials section.