Comparative Effectiveness of COVID-19 Vaccines in Preventing Infections and Disease Progression from SARS-CoV-2 Omicron BA.5 and BA.2, Portugal

We estimated comparative primary and booster vaccine effectiveness (VE) of SARS-CoV-2 Omicron BA.5 and BA.2 lineages against infection and disease progression. During April-June 2022, we implemented a case-case and cohort study and classified lineages using whole-genome sequencing or spike gene target failure. For the case-case study, we estimated the adjusted odds ratios (aORs) of vaccination using a logistic regression. For the cohort study, we estimated VE against disease progression using a penalized logistic regression. We observed no reduced VE for primary (aOR 1.07 [95% CI 0.93-1.23]) or booster (aOR 0.96 [95% CI 0.84-1.09]) vaccination against BA.5 infection. Among BA.5 case-patients, booster VE against progression to hospitalization was lower than that among BA.2 case-patients (VE 77% [95% CI 49%-90%] vs. VE 93% [95% CI 86%-97%]). Although booster vaccination is less effective against BA.5 than against BA.2, it offers substantial protection against progression from BA.5 infection to severe disease.

Description

Author affiliations: Instituto Nacional de Saúde Doutor Ricardo Jorge, Lisbon, Portugal (I. Kislaya, V. Borges, C. Matias Dias, S. Duarte, L. Coelho, R. Ferreira, J. Isidro, M. Pinto, D. Sobral, A. Nunes, D. Santos, L. Vieira, J.P. Gomes, B. Nunes, A. Machado).

Keywords

BA.2 BA.5 COVID-19 Omicron SARS-CoV-2 Coronavirus Disease Death Hospitalization Postinfection Vaccine Effectiveness Respiratory Infections Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine-preventable Diseases Viruses Portugal Infecções Respiratórias Doenças Evitáveis pela Vacinação Determinantes da Saúde e da Doença