The Omicron (B. 1.1. 529) wave in Mexico: Vaccine protection against progression to severe COVID-19 in SARS-CoV-2-infected workers (Preprint)

BACKGROUND The use of administrative and public health surveillance data has been key to follow the Omicron wave during the COVID-19 pandemic. Mexico is among the countries with the most registered deaths during the pandemic and few studies in the region have focused on the effect that the Omicron wave had on hospitalization and death among workers. OBJECTIVE To assess the protection of 7 different COVID-19 vaccine products against progression to severe illness, using administrative and surveillance data of private-sector workers infected with SARS-CoV-2 during the Omicron wave in Mexico from January 2 to March 5, 2022. METHODS We conducted a retrospective cohort evaluation using Respiratory-Disease Short-Term Disability Claims (RD-STDC) registered by the Mexican Social Security Institute (IMSS), linked to COVID-19 surveillance system records and the national COVID-19 vaccination registry. Among all workers who requested RD-STDC and tested positive for SARS-CoV-2, we identified those who developed illness progression (hospitalization or death) attributable to respiratory disease. Vaccinated workers were those who had received the second of a two-dose COVID-19 vaccine series or a single dose of a one-dose product ≥14 days before a positive SARS-CoV-2 test result. We estimated risk ratios for disease progression by vaccination status using Poisson regression models adjusted for sex, age, past RD-STDC, self-reported comorbidities, income, state of residency, and weekly COVID-19 incidence (RRadj). RESULTS During January 2 to March 5, 2022, n=1,410,675 (7%) among 20.1 million private sector workers requested RD-STDC, of which 31.6% had a SARS-CoV-2 test and 445,404 (92.3%) tested positive. Of these workers, 38,676 (11.1%) were unvaccinated and 309,223 (88.9%) received a complete vaccination schedule ≥ 14 days before RD-STDC; 1,198 were hospitalized, and 187 died. Risk of both hospitalization and death were lower among vaccinated persons compared with unvaccinated persons; overall RRadj for hospitalization and death were 0.36 (95% CI 0.32–0.41) and 0.24 (0.17–0.33), respectively. By product, the RRadj for hospitalization was 0.27 (95% CI 0.22–0.33) for Pfizer BioNTech; 0.29 (95% CI 0.15–0.57) for Moderna; 0.32 (95% CI 0.25–0.41) for Sinovac; 0.39 (95% CI 0.34–0.46) for Astra Zeneca; 0.39 (95% CI 0.28–0.53) Sputnik; 0.41 (95% CI 0.24–0.7) for CanSino; and 0.53 (95% CI 0.39–0.72) for Janssen. The RRadj for death was 0.12 (95% CI 0.07–0.19) for Pfizer BioNTech; 0.15 (95% CI 0.06–0.38) for Sputnik; 0.29 (95% CI 0.16–0.53) for Sinovac; 0.30 (95% CI 0.20–0.44) for Astra Zeneca; 0.38 (95% CI 0.1–1.4) for CanSino; and 0.50 (95% CI 0.26–0.97) for Janssen. CONCLUSIONS COVID-19 vaccines were associated with a significant reduction in the risk for progression to severe illness during the Omicron wave in Mexico.