Declining prevalence of antibody positivity to SARS-CoV-2: a community study of 365,000 adults

Abstract

Background The prevalence and persistence of antibodies following a peak SARS-CoV-2 infection provides insights into its spread in the community, the likelihood of reinfection and potential for some level of population immunity. Methods Prevalence of antibody positivity in England, UK (REACT2) with three cross-sectional surveys between late June and September 2020. 365104 adults used a self-administered lateral flow immunoassay (LFIA) test for IgG. A laboratory comparison of LFIA results to neutralization activity in panel of sera was performed. Results There were 17,576 positive tests over the three rounds. Antibody prevalence, adjusted for test characteristics and weighted to the adult population of England, declined from 6.0% [5.8, 6.1], to 4.8% [4.7, 5.0] and 4.4% [4.3, 4.5], a fall of 26.5% [-29.0, -23.8] over the three months of the study. There was a decline between rounds 1 and 3 in all age groups, with the highest prevalence of a positive result and smallest overall decline in positivity in the youngest age group (18-24 years: -14.9% [-21.6, -8.1]), and lowest prevalence and largest decline in the oldest group (75+ years: -39.0% [-50.8, -27.2]); there was no change in antibody positivity between rounds 1 and 3 in healthcare workers (+3.45% [-5.7, +12.7]). The decline from rounds 1 to 3 was largest in those who did not report a history of COVID-19, (-64.0% [-75.6, -52.3]), compared to -22.3% ([-27.0, -17.7]) in those with SARS-CoV-2 infection confirmed on PCR. Discussion These findings provide evidence of variable waning in antibody positivity over time such that, at the start of the second wave of infection in England, only 4.4% of adults had detectable IgG antibodies using an LFIA. Antibody positivity was greater in those who reported a positive PCR and lower in older people and those with asymptomatic infection. These data suggest the possibility of decreasing population immunity and increasing risk of reinfection as detectable antibodies decline in the population.

Challenges in creating herd immunity to SARS-CoV-2 infection by mass vaccination

“…Vaccine efficacies to protect against infection above 80% are desirable, 1 but duration of protection will remain uncertain for a number of years post licensure of COVID-19 vaccines. Preliminary evidence suggests waning antibody titres in those who have recovered from SARS-CoV-2 infection, 2 but antibodies are only one part of the human immune response and acquired immunity to reinfection or the prevention of disease when reinfected. 3 , 4 , 5 Data on immunity to other coronaviruses suggest that immunity to SARS-CoV-2 might be short lived, perhaps 12–18 months in duration.…”

COVID‐19: Current knowledge in clinical features, immunological responses, and vaccine development

“…134 A large-scale community study of 365 000 adults in the United Kingdom found a significant decline in the proportion of the population with detectable antibodies over three-rounds of testing 12, 18, and 24 weeks following the peak of COVID-19 cases. 135 The results of this study suggest that antibody-immunity against SARS-CoV-2 may be waning within the first 6-12 months. However, it is important to note that as this large-scale study was conducted via participants self-pricking and reporting, the results remain to be verified via further investigation.…”

Algorithms for testing COVID-19 focused on use of RT-PCR and high-affinity serological testing: A consensus statement from a panel of Latin American experts

“…In the population aged 75+ years, the drop was 39%. These data suggest that the possibility of decreasing population immunity over time could increase the risk of reinfection ( Ward et al, 2020 ). Currently the importance of antibody decline for reinfection by SARS-CoV-2 is not yet answered and further longitudinal studies are needed.…”