Date of Award

January 2023

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Albert Ko

Abstract

Background: SARS-CoV-2, with its high transmissibility and rapid dissemination, has caused a global public health emergency. The emergence of new variants and mutations of SARSCoV-2 spike protein antigens has led to concerns about immune escape and the potential for reinfection, even in individuals who have been previously infected or vaccinated. Brazil has been severely affected by the pandemic, especially in its densely populated slum areas. Our study aimed to evaluate the association between anti-S IgG antibody levels and subsequent SARS-CoV-2 infection during the Omicron wave in a susceptible community in Salvador, Brazil, to provide insight into the antibody level necessary for effective protection against infection with heterologous variants in similar settings. Methods and findings: We conducted this study in a cohort of 1827 residents of Pau da Lima, Salvador, Brazil. We measured serum levels of IgG against the SARS-CoV-2 Spike protein between July and November 2021. From November 2021 to February 2022, during the first Omicron wave, we performed symptom-based screening and PCR testing to identify new infections. We used logistic regression to estimate the association between antibody levels and subsequent PCR-confirmed infection. Among 210 individuals in the cohort who underwent PCR testing, we did not identify any association between antibody levels and PCR-confirmed infection. Among a subset of 84 individuals who did not receive vaccination between the time of antibody measurement and the time of PCR testing, higher antibody levels were associated with increased odds of PCR-confirmed infection. Conclusion: We did not identify a protective effect of serum anti-S IgG levels on subsequent risk of infection during the Omicron wave. Further studies could address limitations of our study (sample size, confounding) and evaluate the effect of variant-specific antibodies

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This is an Open Access Thesis.

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