The indirect effect of mRNA-based COVID-19 vaccination on healthcare workers’ unvaccinated household members

Jussipekka Salo, Milla Hägg, Mika Kortelainen, Tuija Leino, Tanja Saxell, Markku Siikanen, Lauri Sääksvuori*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

21 Citations (Scopus)
32 Downloads (Pure)

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.

Original languageEnglish
Article number1162
Pages (from-to)1-7
Number of pages7
JournalNature Communications
Volume13
Issue number1
Early online date4 Mar 2022
DOIs
Publication statusPublished - 4 Mar 2022
MoE publication typeA1 Journal article-refereed

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