Reinfection by the SARS-CoV-2 Gamma variant in blood donors in Manaus, Brazil

Abstract

The city of Manaus, north Brazil, was stricken by a severe epidemic of SARS-Cov-2 in March 2020, reaching a seroprevalence of 76% by October 2020. Nevertheless, in late November an abrupt increase in hospitalizations and deaths hit Manaus, causing higher number of deaths compared to the first epidemic wave. It has been hypothesized that virus lineages circulating in the second wave, namely the P.1 variant of concern first detected in early December in Manaus, could be better at evading immunity generated in response to previous infection with other lineages. In order to estimate the reinfection rate during the resurgence of SARS-CoV-2 in Manaus, we tested serial samples from 238 unvaccinated repeat blood donors using a SARS-CoV-2 anti-N IgG chemiluminescence microparticle assay. Blood donors were divided into six groups that reflected the inferred sequence of infection and reinfection with non-P.1 and P.1 variants. We assumed that reinfections induce a recrudescence (or boosting) of plasma anti-N IgG antibody levels, yielding a V-shaped time series of antibody reactivity levels. We infer that 16.9% (95% CI [9.48%, 28.5%]) of all presumed P.1 infections that were observed in 2021 were reinfections. If we also include cases of probable or possible reinfections (defined by considering the time period when the antibody levels are expected to grow after recovery and the range of half-lives for antibody waning after seroconversion), these percentages increase respectively to 25.8% (95% CI [16.7%, 37.4%]), and 31.0% (95% CI [21.4%, 42.5%]). Our data suggest that reinfection due to P.1 is common and more frequent than what has been detected by traditional epidemiologic, molecular and genomic surveillance of clinical cases.

SARS‐CoV‐2 antibody persistence in COVID‐19 convalescent plasma donors: Dependency on assay format and applicability to serosurveillance

“…31 Such boosting will be particularly apparent with assays that are prone to waning, such as the Abbott NC and RBD IgG assays and pseudovirus RVPN assay. 32 Hence, different assays and different combinations of SARS-CoV-2 antibody assays will be needed to address the multiple important questions that are arising as the pandemic and mitigation strategies evolve. There is evolving appreciation of different applications or use cases for serological testing that will require different assays/algorithms for the next phase of COVID-19 pandemic response.…”

Modelling of Waning of Immunity and Reinfection Induced Antibody Boosting of SARS-CoV-2 in Manaus, Brazil

“…The mathematical models of infectious diseases have been playing a pivotal role in understanding emerging and re-emerging infectious disease outbreaks, evaluating strategies for effective prevention and control measures, as well as providing suggestions to policymakers on how to effectively control the epidemics in a timely fashion. In this paper, we develop a simple conceptual model to qualitatively reproduce the observed dynamics of SARS-CoV-2 in Manaus with reinfection [9]. The model was able to capture the observed dynamics on reinfection by a new variant [9,[19][20][21].…”

“…Prete et al [9] studied the antibody level (IgG) of 238 repeated blood donors in Manaus, and found that some of them showed evidence of being infected with a wild strain in the first wave, i.e., an increase in their IgG level in April-May 2020. Others showed evidence of being infected with the P.1 strain in the second wave, i.e., elevated IgG levels from December 2020 to January 2021.…”

“…The reinfected individuals could be infectious, with reduced infectiousness which is controlled by a parameter, ε. A set of parameter values were selected such that we can qualitatively reproduce the two wave patterns which occurred in Manaus and the observed reinfection ratio reported by Prete et al [9].…”

“…These numbers are implausible since only three confirmed reinfections were reported in the whole Amazonas province, including Manaus [8]. Prete et al [9] reported a reinfection ratio at 3-13.9% based on serological antibody level (IgG) data from 238 repeated blood donors. Their finding motivated us to formulate a model to examine the possible role of reinfection in causing the two waves in Manaus.…”