Título

LIVE: a real-world, test-negative case-control study of AZD1222 vaccine effectiveness (VE) against COVID-19 hospitalization in Latin America

Introdução

While AZD1222 (ChAdOx1 nCoV-19) VE against severe COVID-19 (73–94%) has been well characterized in many countries, real-world evidence is limited in Latin America–particularly in pregnant, elderly, and immunocompromized (IC) individuals. Additionally, several Latin American countries feature unique primary vaccination schedules (including extensions for IC individuals), booster schedules, and vaccine availability. VE may change with vaccine waning and evolving variants of concern (VOC). The LIVE study (NCT05282017) will estimate VE of AZD1222 and other vaccines against hospitalization due to severe COVID-19, by VOC, and in subgroups of interest.

Material e Método

LIVE is an observational study of people with COVID-19 and a test-negative case-control group. Adults (≥18 years) hospitalized with COVID-19-like symptoms from six Latin American countries (Argentina, Brazil, Colombia, Costa Rica, Mexico, and Panama) are eligible. Those positive for SARS-CoV-2 by RT-PCR or rapid antigen test between 14 days prior to and 1 day after admission will form the test-positive group. Covariate data will be collected to control for confounding analyses and identify those in subgroups of interest, including hospital workers, IC, elderly, and pregnant participants. Crude and adjusted VE will be estimated for each country and subgroup; VE is defined as (1- odds ratio of vaccination among participants in the test-positive group vs the test-negative group)*100. Primary objectives are to estimate VE against hospitalization among participants vaccinated with ≥1 dose of AZD1222, and among those fully vaccinated with AZD1222. Secondary objectives include variant-specific VE against hospitalization in those who have received any COVID-19 vaccine, with assessments by vaccine received, number of doses (including booster and extended primary schedules), dose interval, time since vaccination, country, age, disease severity and outcome, comorbidity, and other subgroups of interest. Characterization of breakthrough SARS-CoV-2 infections is an exploratory objective.

Resultados

Enrollment began February 2022, and as of July 8th, 96 participants have enrolled. Initial results are expected H2 2022.

Discussão e Conclusões

LIVE will provide evidence on VE against hospitalization from COVID-19, including impacts of heterologous and extended dosing schedules. VE of AZD1222 and other vaccines in the context of VOC circulating in Latin America, including Omicron subvariants, and in understudied subgroups, will help inform future vaccination programs.

Palavras Chave

COVID-19, SARS-CoV-2, AZD1222, COVID-19 Vaccine, Vaccine Effectiveness, Real-world Evidence, Latin America