Vaccine Coverage and Effectiveness Against Laboratory-Confirmed Symptomatic and Severe COVID-19 in Indigenous People in Brazil: A Cohort Study

Background: We estimated the coverage and effectiveness of Covid-19 vaccines against laboratory-confirmed Covid-19 cases among indigenous people in Brazil.Methods: We linked nationwide immunization data with symptomatic and Severe Acute Respiratory Infection records and studied a cohort of vaccinated indigenous people aged ≥5 years between 18th Jan 2021 and 1st Mar 2022. We estimated the Covid-19 vaccination coverage and used Poisson regression to calculate the vaccine effectiveness (VE) of CoronaVac, ChAdOx1, and BNT162b2 against Covid-19 laboratory-confirmed symptomatic and severe cases (i.e., mortality, hospitalisation, and hospital-progression to Intensive Care Unit (ICU) or death). VE was estimated as (1-RR)*100, comparing unexposed (<14 days after the 1st dose), to partially (≥14 days after 1st dose to <14 days after 2nd dose), or fully vaccinated (≥14 days after 2nd dose).Findings: By 1st Mar 2022, 48·7% (35·0-62·3) of eligible indigenous people vs 74·8% (57·9-91·8) overall Brazilians had been fully vaccinated for Covid-19. Among the 370,092 indigenous subjects studied, we detected 1951 Covid-19 cases, of which 105 were hospitalised and 35 died. VE for the three Covid-19 vaccines combined was 53% (95%CI:44-60%) for symptomatic cases, 53% (95%CI:-56-86%) for mortality and 41% (95%CI:-35-75%) for hospitalisation. Among hospitalised patients, VE was 87% (95%CI:27-98%) for progression to ICU and 96% (95%CI: 90-99%) for death.Interpretation: Lower coverage but similar Covid-19 vaccine effectiveness among indigenous people than overall Brazilians suggest the need to expand access, timely vaccination, especially among children and adolescents, and urgently offer booster doses to achieve a great level of protection among this group.Funding Information: None.Declaration of Interests: We declare no competing interests.Ethics Approval Statement: The Brazilian National Commission on Research Ethics (CONEP) approved this study (n. 4.921.308). The study used an anonymised secondary dataset, which complies with the Brazilian General Personal Data Protection Law (LGPD).