Abstract
Objectives: To estimate vaccine effectiveness after the first and second dose of ChAdOx1 nCoV-19 against symptomatic COVID-19 and infection in a socially vulnerable community in Brazil when Gamma and Delta were the predominant variants circulating.
Methods: We conducted a test-negative study in the community Complexo da Maré, the largest group of slums (n = 16) in Rio de Janeiro, Brazil, from January 17, 2021 to November 27, 2021. We selected RT-qPCR positive and negative tests from a broad community testing program. The primary outcome was symptomatic COVID-19 (positive RT-qPCR test with at least one symptom) and the secondary outcome was infection (any positive RT-qPCR test). Vaccine effectiveness was estimated as 1 – OR, which was obtained from adjusted logistic regression models.
Results: We included 10 077 RT-qPCR tests (6,394, 64% from symptomatic and 3,683, 36% from asymptomatic individuals). The mean age was 40 (SD: 14) years, and the median time between vaccination and RT-qPCR testing among vaccinated was 41 (25-75 percentile: 21-62) days for the first dose and 36 (25-75 percentile: 17-59) days for the second dose. Adjusted vaccine effectiveness against symptomatic COVID-19 was 31.6% (95% CI, 12.0-46.8) 21 days after the first dose and 65.1% (95% CI, 40.9-79.4) 14 days after the second dose. Adjusted vaccine effectiveness against COVID-19 infection was 31.0% (95% CI, 12.7-45.5) 21 days after the first dose and 59.0% (95% CI, 33.1-74.8) 14 days after the second dose.
Discussion: ChAdOx1 nCoV-19 was effective in reducing symptomatic COVID-19 in a socially vulnerable community in Brazil when Gamma and Delta were the predominant variants circulating.
Keywords: Brazil; COVID-19; Test-negative; Vaccine; Vulnerable community.
【저자키워드】 COVID-19, Brazil, Vaccine, Test-negative, Vulnerable community., 【초록키워드】 Brazil, vaccination, variant, Infection, Delta, Symptom, RT-qPCR, Asymptomatic individuals, COVID-19 infection, symptomatic, Effectiveness, Community, Gamma, age, Rio de Janeiro, ChAdOx1, ChAdOx1 nCoV-19, symptomatic COVID-19, Primary outcome, 95% CI, median time, second dose, first dose, secondary outcome, circulating, logistic regression models, positive, qPCR test, RT-qPCR test, first and second dose, negative test, effective, selected, conducted, adjusted, reducing, predominant, was obtained, ChAdOx1 nCoV-19 against, the median, 【제목키워드】 Effectiveness, Community, ChAdOx1 nCoV-19 against,