High anti-SARS-CoV-2 antibody seroconversion rates before the second wave in Manaus, Brazil, and the protective effect of social behaviour measures: results from the prospective DETECTCoV-19 cohort
Authors: Pritesh Lalwani, Roger V Araujo-Castillo, Christian A Ganoza, Bárbara Batista Salgado, Ivanildo Vieira Pereira Filho, Danielle Severino Sena da Silva, Thiago Barros do Nascimento de Morais, Maele Ferreira Jordão, Jessica Vanina Ortiz, Aguyda Rayany Cavalcante Barbosa, Wlademir Braga Salgado Sobrinho, Isabelle Bezerra Cordeiro, Júlio Nino de Souza Neto, Enedina Nogueira de Assunção, Cristiano Fernandes da Costa, Pedro Elias de Souza, Bernardino Claudio de Albuquerque, Spartaco Astofi-Filho, Jaila Dias Borges Lalwani, Aldina Iacy Paulain Holanda, Ana Lúcia Silva Gomes, Ana Paula Souza de França, André Victor Rabelo Monteiro, Andressa dos Passos Santos, Antônia de Sousa Teixeira, Antônio Vinicius Soares de Souza, Beatriz Pinheiro, Bianca Pires dos Santos, Brenda Pereira Farias, Bruno Nicolau Paulino, Caio Lúcio Andreola da Silva, Cinthya Iamile Frithz Brandão de Oliveira, Dalila de Alcântara Martins, Eline Araújo de Oliveira, Elisson Denny da Costa Carvalho, Evillyn Fernandes Da Costa, Fernanda Guilhon Simplicio, Fernanda Serrão Pereira, Gabriele Pimentel Sinimbu, Genilton de Oliveira Cardenes, Giane Alves da Silva, Iago Sampaio Fernandes da Costa, Ingrid Silva Correia, Ilia Gilmara Carvalho dos Santos, Jackeline Vieira Guimarães, Jessica Samile Batista Pinheiro, Juliana Correa Romana, Josineide de Oliveira Novo França, Kerollen Runa Pinto, Maria Fiamma Farias Freitas, Marne Carvalho de Vasconcellos, Marizete Candido Moraes, Matheus da Silva Damasceno, Michelle Araújo Ruiz, Milena Maria Cardoso de Lemos, Neila Soares Picanço, Rayara Gonzaga Maia, Regiane Carneiro Bezerra, Romeu Santos de Souza, Susy Cavalcante Harjani, Vitor Batista de Souza, Wellington Barbosa de Melo
Journal: The Lancet Global Health (2021)

The city of Manaus, Brazil, has seen two collapses of the health system due to the COVID-19 pandemic. We report anti-SARS-CoV-2 nucleocapsid IgG antibody seroconversion rates and associated risk factors in Manaus residents before the second wave of the epidemic in Brazil.A convenience sample of adult (aged ≥18 years) residents of Manaus was recruited through online and university website advertising into the DETECTCoV-19 study cohort. The current analysis of seroconversion included a subgroup of DETECTCoV-19 participants who had at least two serum sample collections separated by at least 4 weeks between Aug 19 and Oct 2, 2020 (visit 1), and Oct 19 and Nov 27, 2020 (visit 2). Those who reported (or had no data on) having a COVID-19 diagnosis before visit 1, and who were positive for anti-SARS-CoV-2 nucleocapsid IgG antibodies at visit 1 were excluded. Using an in-house ELISA, the reactivity index (RI; calculated as the optical density ratio of the sample to the negative control) for serum anti-SARS-CoV-2 nucleocapsid IgG antibodies was measured at both visits. We calculated the incidence of seroconversion (defined as RI values ≤1·5 at visit 1 and ≥1·5 at visit 2, and a ratio >2 between the visit 2 and visit 1 RI values) during the study period, as well as incidence rate ratios (IRRs) through cluster-corrected and adjusted Poisson regression models to analyse associations between seroconversion and variables related to sociodemographic characteristics, health access, comorbidities, COVID-19 exposure, protective behaviours, and symptoms.2496 DETECTCoV-19 cohort participants returned for a follow-up visit between Oct 19 and Nov 27, 2020, of whom 204 reported having COVID-19 before the first visit and 24 had no data regarding previous disease status. 559 participants were seropositive for anti-SARS-CoV-2 nucleocapsid IgG antibodies at baseline. Of the remaining 1709 participants who were seronegative at baseline, 71 did not meet the criteria for seroconversion and were excluded from the analyses. Among the remaining 1638 participants who were seronegative at baseline, 214 showed seroconversion at visit 2. The seroconversion incidence was 13·06% (95% CI 11·52-14·79) overall and 6·78% (5·61-8·10) for symptomatic seroconversion, over a median follow-up period of 57 days (IQR 54-61). 48·1% of seroconversion events were estimated to be asymptomatic. The sample had higher proportions of affluent and higher-educated people than those reported for the Manaus city population. In the fully adjusted and corrected model, risk factors for seroconversion before visit 2 were having a COVID-19 case in the household (IRR 1·49 [95% CI 1·21-1·83]), not wearing a mask during contact with a person with COVID-19 (1·25 [1·09-1·45]), relaxation of physical distancing (1·31 [1·05-1·64]), and having flu-like symptoms (1·79 [1·23-2·59]) or a COVID-19 diagnosis (3·57 [2·27-5·63]) between the first and second visits, whereas working remotely was associated with lower incidence (0·74 [0·56-0·97]).An intense infection transmission period preceded the second wave of COVID-19 in Manaus. Several modifiable behaviours increased the risk of seroconversion, including non-compliance with non-pharmaceutical interventions measures such as not wearing a mask during contact, relaxation of protective measures, and non-remote working. Increased testing in high-transmission areas is needed to provide timely information about ongoing transmission and aid appropriate implementation of transmission mitigation measures.Ministry of Education, Brazil; Fundação de Amparo à Pesquisa do Estado do Amazonas; Pan American Health Organization (PAHO)/WHO.