Impacts of vaccination, school attendance, and nutrition on SARS-CoV-2 antibody titer in a prospective birth cohort in Brazil.

In this study, we examine the association between COVID-19 vaccination and antibody titer and whether this association varies by nutritional status and duration of school attendance using linear regression models applied to seven-year-old children from the 2015 Pelotas (Brazil) Birth Cohort (n = 2956). Antibody titers were 0.29 optical density (OD) titer units higher among vaccinated compared with unvaccinated children (95 % CI: 0.24, 0.34). Duration of school enrollment was associated with increased antibody titer, with each month being associated with a 0.15 unit increase in OD titer (95 % CI: 0.14, 0.16). Stunting was associated with lower COVID-19 titers among unvaccinated children (-0.10, 95 % CI: -0.21,0.004), but not among vaccinated children. Stunted children may have poorer immune responses to natural infection, but vaccination can overcome this deficit. Population-wide follow-up vaccination may be beneficial, particularly prior to school entry and for stunted children to reduce the risk of natural infection.