The indirect effect of mRNA-based COVID-19 vaccination on healthcare workers' unvaccinated household members
- PMID: 35246536
- PMCID: PMC8897446
- DOI: 10.1038/s41467-022-28825-4
The indirect effect of mRNA-based COVID-19 vaccination on healthcare workers' unvaccinated household members
Abstract
Mass vaccination is effective in reducing SARS-CoV-2 infections among vaccinated individuals. However, it remains unclear how effectively COVID-19 vaccines prevent people from spreading the virus to their close contacts. Using nationwide administrative datasets on SARS-CoV-2 infections, vaccination records, demographics, and unique household IDs, we conducted an observational cohort study to estimate the direct and indirect effectiveness of mRNA-based COVID-19 vaccines in reducing infections among vaccinated healthcare workers and their unvaccinated household members. Our estimates for adults imply indirect effectiveness of 39.1% (95% CI: -7.1% to 65.3%) two weeks and 39.0% (95% CI: 18.9% to 54.0%) eight weeks after the second dose. We find that the indirect effect of mRNA-based COVID-19 vaccines within households is smaller for unvaccinated children than for adults and statistically insignificant. Here, we show that mRNA-based COVID-19 vaccines are associated with a reduction in SARS-CoV-2 infections not only among vaccinated individuals but also among unvaccinated adult household members in a real-world setting.
© 2022. The Author(s).
Conflict of interest statement
M.K. declares to his employer a grant, but no personal support or financial relationship, from Pfizer during the conduct of the study. The other authors have no competing interest to declare.
Figures
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