Next, 6577 (90.6%) reported White ethnicity, 127 (1.8%) working in patient-facing healthcare and 1592 (21.9%) having a long-term health condition. The median age of these 7256 participants was 47 (IQR 34–59) years and 3874 (53.4%) were female (Table 1). Analysis included the 7256/19,588 (37%) participants with at least one anti-spike IgG antibody measurement within days of the start of their first infection episode, who contributed 14,552 antibody measurements (median 2, IQR 1–3, range 1–10 excluding measurements from 3 days after first vaccination) (Supplementary Fig. Then, 19,588 (4.2%) participants ≥16 years were ever PCR-positive, 92 (0.5%) with a second episode >120 days after their first PCR-positive result (median 149, IQR 134–174 days later). We used the Office for National Statistics (ONS) COVID-19 Infection Survey (CIS), a large community-based survey representative of UK’s general population, to investigate predictors of seroconversion following SARS-CoV-2 infection, identify anti-spike IgG antibody trajectories and examine the peak and duration of IgG antibody responses, in particular considering the impact of demographic factors, PCR cycle threshold (Ct) values (inversely related to viral load) and self-reported symptoms on post-infection antibody responses.įrom 26 April 2020 to 14 June 2021, 467,450 participants had one or more throat and nose swab study results (median 10, interquartile range (IQR) 8–12) during a median (IQR) 221 (141–251) days of follow-up. Most studies have had small to moderate sample sizes or specific sub-populations large-scale representative population studies are limited. Similarly, anti-nucleocapsid IgG half-lives have been estimated between 35 and 85 days 15, 19, 20, 22. Estimates for the half-life of anti-spike IgG antibodies (associated with neutralizing activity 16) vary from 36 to 244 days 15, 17, 18, 19, 20, 21, 22, 23. However, the contribution of other factors, including viral load, has not been comprehensively assessed.Īmong those who do seroconvert, data on the trajectory and duration of antibody responses to different SARS-CoV-2 antigens vary, partly reflecting assay-dependent differences even where similar viral antigens are studied 14, 15, as well as differences in the populations and disease groups investigated. The absence of seroconversion is more common following mild vs. However, 5–22% of individuals remain seronegative following infection 11, 12, 13. Seroconversion to viral spike and nucleocapsid antigens usually happens within 1–3 weeks after SARS-CoV-2 infection 6, 7, 8, with peak antibody levels achieved in 4–5 weeks 9, 10. The duration of post-infection immunity has important implications for the future of the pandemic and vaccination policy 5. However, in the months following infection, re-infection is uncommon and anti-spikeSARS-CoV-2 antibodies are associated with protection 2, 3, 4. Till June 2021, over 170 million severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and over 3 million associated deaths have been reported globally 1. These estimates could inform planning for vaccination booster strategies. We estimated antibody levels associated with protection against reinfection likely last 1.5-2 years on average, with levels associated with protection from severe infection present for several years. The estimated anti-spike IgG half-life was 184 days, being longer in females and those of white ethnicity. Among those who seroconverted, using Bayesian linear mixed models, the estimated anti-spike IgG peak level was 7.3-fold higher than the level previously associated with 50% protection against reinfection, with higher peak levels in older participants and those of non-white ethnicity. lower viral burden), and less frequently reported any symptoms. A latent class model classified 24% of participants as ‘non-responders’ not developing anti-spike antibodies, who were older, had higher SARS-CoV-2 cycle threshold values during infection (i.e. Here we estimated antibody response after SARS-CoV-2 infection in the general population using representative data from 7,256 United Kingdom COVID-19 infection survey participants who had positive swab SARS-CoV-2 PCR tests from 26-April-2020 to 14-June-2021. Understanding the trajectory, duration, and determinants of antibody responses after SARS-CoV-2 infection can inform subsequent protection and risk of reinfection, however large-scale representative studies are limited.
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