The duration, dynamics and determinants of SARS-CoV-2 antibody responses in individual healthcare workers

Abstract

Background SARS-CoV-2 IgG antibody measurements can be used to estimate the proportion of a population exposed or infected and may be informative about the risk of future infection. Previous estimates of the duration of antibody responses vary. Methods We present 6 months of data from a longitudinal seroprevalence study of 3217 UK healthcare workers (HCWs). Serial measurements of IgG antibodies to SARS-CoV-2 nucleocapsid were obtained. Bayesian mixed linear models were used to investigate antibody waning and associations with age, gender, ethnicity, previous symptoms and PCR results. Results In this cohort of working age HCWs, antibody levels rose to a peak at 24 (95% credibility interval, CrI 19-31) days post-first positive PCR test, before beginning to fall. Considering 452 IgG seropositive HCWs over a median of 121 days (maximum 171 days) from their maximum positive IgG titre, the mean estimated antibody half-life was 85 (95%CrI, 81-90) days. The estimated mean time to loss of a positive antibody result was 137 (95%CrI 127-148) days. We observed variation between individuals; higher maximum observed IgG titres were associated with longer estimated antibody half-lives. Increasing age, Asian ethnicity and prior self-reported symptoms were independently associated with higher maximum antibody levels, and increasing age and a positive PCR test undertaken for symptoms with longer antibody half-lives. Conclusion IgG antibody levels to SARS-CoV-2 nucleocapsid wane within months, and faster in younger adults and those without symptoms. Ongoing longitudinal studies are required to track the long-term duration of antibody levels and their association with immunity to SARS-CoV-2 reinfection.

Antibody Status and Incidence of SARS-CoV-2 Infection in Health Care Workers

“…In addition to the 24 seronegative health care workers with a previous positive PCR test, it is likely that other health care workers with baseline titers below assay thresholds, which were set to ensure high specificity, 23 had been previously infected with SARS-CoV-2 and had low peak postinfection titers or rising or waning responses at testing. 5 …”

“…Asymptomatic health care workers were invited to participate in voluntary nasal and oropharyngeal swab PCR testing every 2 weeks and serologic testing every 2 months (with some participating more frequently for related studies) beginning on April 23, 2020, as previously described. 5 , 22 Staff were followed until November 30, 2020. Deidentified data were obtained from the Infections in Oxfordshire Research Database, which has generic research ethics committee, Health Research Authority, and Confidentiality Advisory Group approvals.…”

SARS-CoV-2 re-infection risk in Austria

“…1,2 A key question concerning measures against COVID-19 is the strength and durability of immunity against this disease in individuals previously infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). [3][4][5][6][7][8][9][10] Vaccination strategies, considerations regarding herd immunity, and overall simulations for the pandemic depend on the efficacy and the time course of immunity against COVID-19. 5 Data on immune responses to COVID-19 are limited by knowledge gaps regarding their dynamics over time and their clinical significance with reference to protection against re-infections.…”

“…5 Data on immune responses to COVID-19 are limited by knowledge gaps regarding their dynamics over time and their clinical significance with reference to protection against re-infections. [3][4][5][6][7][8][9][10] There is evidence for re-infections from numerous case reports, but it is occasionally challenging to differentiate true re-infections from prolonged viral shedding that may last for up to about 4 months. 5,11,12 Notably, a study of 12,541 health care workers in the UK recently found major protection against re-infection for those who had anti-SARS-CoV-2 antibodies determined by anti-spike and anti-nucleocapsid assays versus those who did not.…”

Impact of reproduction number on the multiwave spreading dynamics of COVID-19 with temporary immunity: A mathematical model

“… Kowitdamrong et al (2020) report upto 20 percent post-infection seroconversion failure rate in mild or asymptomatic patients in Thailand – they do not document any reinfection cases. Lumley et al (2020) have very recently reported an antibody half-life of 85 days and a median time of 137 days to loss of positivity; these results are corrborated by Robertson et al (2020) . A few potential cases of reinfection have also been reported in media for some time before the first documented case – in these instances, the evidence is not fully credible ( McCamon, 2020 , Saplakoglu, 2020 , Ackerly, 2020 ).…”