Apparent reinfections in Brazil

 

Resurgence of COVID-19 in Manaus, Brazil, despite high seroprevalence Departamento de Molestias Infecciosas e Parasitarias and Instituto de Medicina Tropical da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Department of Infectious Diseases and Parasitises and Institute of Tropical Medicine of the Faculty of Medicine of the University of São Paulo, São Paulo, https://www.thelancet.com/journals/la...

​ European and Asian countries Second wave, consistent with many remaining susceptible Manaus, Brazil Blood donors, 76% had been infected by October 2020 Also, estimated attack rates in Amazon Basin, 70% Estimated SARS-CoV-2 attack rate in Manaus, above theoretical herd immunity threshold of 67% (based on a reproduction number of 3) But January 2021 Manaus hospital admissions, 3,431 (552 in Dec 1–19, 2020) May to November, relaxation of control measures, low admissions for 7 months There are at least four non-mutually exclusive possible explanations for the resurgence of COVID-19 in Manaus. Why a resurgence of cases? First factor, first wave overestimated Attack rate could have been overestimated during the first wave June, seroprevalence, 52·5% Second factor, waning immunity Waning of IgG antibody titres observed in blood donors Most of the SARS-CoV-2 infections in Manaus occurred 7–8 months before resurgence in January, 2021 (No observed behaviour change in Manaus, reduced population mobility) If resurgence in Manaus is due to waning, similar resurgence everywhere Third factor, antigenic escape New SARS-CoV-2 lineages Circulating in Brazil, B.1.1.7 and P.1 P.1 detected in Manaus on Jan 12, 2021 P.1 lineage, accrued ten unique spike protein mutations, Including E484K P.2 lineage also detected Manaus P.2 independently accrued the spike E484K mutation In-vitro evidence that E484K mutation reduces neutralisation by polyclonal antibodies in convalescent sera Antigenic escape Fourth factor, increased transmissibility SARS-CoV-2 lineages circulating in the second wave might have higher inherent transmissibility Eg. Relative prevalence of P.1 lineage, up to 42% by December, 2020 P.1 lineage Shares several independently acquired mutations B.1.1.7 (N501) B.1.325 (K417N/T, E484K, N501Y) Conclusions Variants need to be quickly investigated Genetic, immunological, clinical, and epidemiological characteristics Serological and genomic surveillance in Manaus is a priority Determining vaccine is also crucial Rapid sharing of lineage-specific frequencies underlying reinfection