Author:
Prete Carlos A.,Buss Lewis F.,Buccheri Renata,Abrahim Claudia M. M.,Salomon Tassila,Crispim Myuki A. E.,Oikawa Marcio K.,Grebe Eduard,da Costa Allyson G.,Fraiji Nelson A.,do P. S. S. Carvalho Maria,Whittaker Charles,Alexander Neal,Faria Nuno R.,Dye Christopher,Nascimento Vítor H.,Busch Michael P.,Sabino Ester Cerdeira
Abstract
Abstract
Background
The city of Manaus, north Brazil, was stricken by a second epidemic wave of SARS-CoV-2 despite high seroprevalence estimates, coinciding with the emergence of the Gamma (P.1) variant. Reinfections were postulated as a partial explanation for the second surge. However, accurate calculation of reinfection rates is difficult when stringent criteria as two time-separated RT-PCR tests and/or genome sequencing are required. To estimate the proportion of reinfections caused by Gamma during the second wave in Manaus and the protection conferred by previous infection, we identified anti-SARS-CoV-2 antibody boosting in repeat blood donors as a mean to infer reinfection.
Methods
We tested serial blood samples from unvaccinated repeat blood donors in Manaus for the presence of anti-SARS-CoV-2 IgG antibodies using two assays that display waning in early convalescence, enabling the detection of reinfection-induced boosting. Donors were required to have three or more donations, being at least one during each epidemic wave. We propose a strict serological definition of reinfection (reactivity boosting following waning like a V-shaped curve in both assays or three spaced boostings), probable (two separate boosting events) and possible (reinfection detected by only one assay) reinfections. The serial samples were used to divide donors into six groups defined based on the inferred sequence of infection and reinfection with non-Gamma and Gamma variants.
Results
From 3655 repeat blood donors, 238 met all inclusion criteria, and 223 had enough residual sample volume to perform both serological assays. We found 13.6% (95% CI 7.0–24.5%) of all presumed Gamma infections that were observed in 2021 were reinfections. If we also include cases of probable or possible reinfections, these percentages increase respectively to 22.7% (95% CI 14.3–34.2%) and 39.3% (95% CI 29.5–50.0%). Previous infection conferred a protection against reinfection of 85.3% (95% CI 71.3–92.7%), decreasing to respectively 72.5% (95% CI 54.7–83.6%) and 39.5% (95% CI 14.1–57.8%) if probable and possible reinfections are included.
Conclusions
Reinfection by Gamma is common and may play a significant role in epidemics where Gamma is prevalent, highlighting the continued threat variants of concern pose even to settings previously hit by substantial epidemics.
Funder
Fundação de Amparo à Pesquisa do Estado de São Paulo
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Fundação Faculdade de Medicina
Wellcome Trust
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Itaú Unibanco - Todos pela Saúde
Medical Research Council
Blood Institute Recipient Epidemiology and Donor Evaluation Study
Publisher
Springer Science and Business Media LLC
Cited by
14 articles.
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