SARS-CoV-2 seroprevalence and respiratory disease disability claims in Mexico City Metropolitan Area.

OBJECTIVE: To characterize the impact of SARS-CoV-2 infection in workers from an essential large-scale company in the Greater Mexico City Metropolitan Area using point prevalence of acute infection, point prevalence of past infection through serum antibodies and respiratory disease short-term disability claims (RD-STDC). MATERIALS AND METHODS: Four randomized surveys, three during 2020 before and one after (December 2021) vaccines' availability. OUTCOMES: point prevalence of acute infection through saliva PCR (polymerase chain reaction) testing, point prevalence of past infection through serum antibodies against Covid-19, RD-STDC and prevalence of symptoms during the previous six months. RESULTS: Prevalence of SARS-CoV-2 cases was 1.29-4.88%, on average, a quarter of participants pre-vaccination were seropositive; over half of participants with a RD-STDC had antibodies. The odds of having antibodies were 6-7 times more among workers with an RD-STDC. CONCLUSIONS: High antibody levels against Covid-19 in this study population reflects that coverage is high among workers in this industry. STDCs are a useful tool to track workplace epidemics.

Assessing the real-world effectiveness of five SARS-CoV-2 vaccines in a cohort of Mexican pensioners: a nationwide nested test-negative design study.

Background: Despite the extensive distribution of COVID-19 vaccines across Latin America, research on their real-world performance remains limited. We aimed to evaluate the effectiveness of five vaccines (BNT162b2, AZD1222, CoronaVac, Gam-COVID-Vac, and Ad5-nCoV) in a cohort of 2,559,792 pensioners covered by the Mexican Institute of Social Security. Methods: We conducted a nested test-negative design study on 28,271 individuals tested for SARS-CoV-2 infection between April and November 2021, accounting for 29,226 separate episodes. We used mixed-effects logistic regression models to estimate the vaccine effectiveness (VE) in fully vaccinated individuals for symptomatic infection, hospitalization, severe disease, and death. Findings: The median age of the study population was 70 years (interquartile range 65-76) and 76.4% (21,598/28,271) were male. VE rates were 56.3%, 75.3%, 79.7%, and 79.8% against symptomatic infection (95% confidence interval [CI]: 53.5-59.0), hospitalization (95% CI: 73.4-77.0), severe disease (95% CI: 78.0-81.3), and death (95% CI: 78.1-81.4), respectively. When evaluating vaccines individually, all showed moderate to high VE, with the best being BNT162b2 (symptomatic infection, 69.8%, 95% CI: 67.3-72.0; hospitalization, 84.1%, 95% CI: 82.5-85.6; severe disease, 88.2%, 95% CI: 86.7-89.5; and death, 88.3%, 95% CI: 86.9-89.6) and Gam-COVID-Vac (symptomatic infection, 70.0%, 95% CI: 64.8-74.4; hospitalization, 86.8%, 95% CI: 83.7-89.3; severe disease, 91.9%, 95% CI: 89.4-93.9; and death, 92.0%, 95% CI: 89.5-93.9). Interpretation: All five SARS-CoV-2 vaccines available for this population showed moderate to high levels of protection against COVID-19 and its progression to severe outcomes. Funding: Fundación IMSS, México.