artículo científico
Estimating vaccine effectiveness against SARS‑CoV‑2 infection, hospitalization and death from ecologic data in Costa Rica
Fecha
2022-10-02Registro en:
1471-2334
10.1186/s12879-022-07740-5
Autor
Fantin, Romain Clement
Herrero, Rolando
Hildesheim, Allan
Barboza Solís, Cristina
Aparicio Llanos, Amada
Prevots, D. Rebecca
Pfeiffer, Ruth M.
Gail, Mitchell H.
Institución
Resumen
Abstract
Background: Clinical trials and individual-level observational data in Israel demonstrated approximately 95% effectiveness
of mRNA-based vaccines against symptomatic SARS-CoV-2 infection. Individual-level data are not available in
many countries, particularly low- and middle- income countries. Using a novel Poisson regression model, we analyzed
ecologic data in Costa Rica to estimate vaccine effectiveness and assess the usefulness of this approach.
Methods: We used national data from December 1, 2020 to May 13, 2021 to ascertain incidence, hospitalizations and
deaths within ecologic units defined by 14 age groups, gender, 105 geographic areas, and day of the epidemic. Within
each unit we used the proportions of the population with one and with two vaccinations, primarily tozinameran.
Using a non-standard Poisson regression model that included an ecologic-unit-specific rate factor to describe rates
without vaccination and a factor that depended on vaccine effectiveness parameters and proportions vaccinated, we
estimated vaccine effectiveness.
Results: In 3.621 million persons aged 20 or older, there were 125,031 incident cases, 7716 hospitalizations, and 1929
deaths following SARS-CoV-2 diagnosis; 73% of those aged ≥ 75 years received two doses. For one dose, estimated
effectiveness was 59% (95% confidence interval 53% to 64%) for SARS-CoV-2 incidence, 76% (68% to 85%) for hospitalizations,
and 63% (47% to 80%) for deaths. For two doses, the respective estimates of effectiveness were 93% (90%
to 96%), 100% (97% to 100%), and 100% (97% to 100%).
Conclusions: These effectiveness estimates agree well with findings from clinical trials and individual-level observational
studies and indicate high effectiveness in the general population of Costa Rica. This novel statistical approach is
promising for countries where ecologic, but not individual-level, data are available. The method could also be adapted
to monitor vaccine effectiveness over calendar time.