Published on in Vol 8, No 5 (2022): May
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/35054, first published
.
![The Effectiveness of Pfizer-BioNTech and Oxford-AstraZeneca Vaccines to Prevent Severe COVID-19 in Costa Rica: Nationwide, Ecological Study of Hospitalization Prevalence The Effectiveness of Pfizer-BioNTech and Oxford-AstraZeneca Vaccines to Prevent Severe COVID-19 in Costa Rica: Nationwide, Ecological Study of Hospitalization Prevalence](https://asset.jmir.pub/assets/0b8e18973b256acdb9c6e63617f2698e.png 480w,https://asset.jmir.pub/assets/0b8e18973b256acdb9c6e63617f2698e.png 960w,https://asset.jmir.pub/assets/0b8e18973b256acdb9c6e63617f2698e.png 1920w,https://asset.jmir.pub/assets/0b8e18973b256acdb9c6e63617f2698e.png 2500w)
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