Helsinki GSE Situation Room study: Coronavirus vaccines also protect unvaccinated family members

June 2, 2021

According to the results of the study, the Pfizer-BioNTech and Moderna coronavirus vaccines, both of which are in use in Finland, also protect unvaccinated family members.

A study by Helsinki GSE used material from Finnish registers to ascertain the risk facing family members of people who have been vaccinated against the coronavirus of contracting the disease. According to the results of the study, the Pfizer-BioNTech and Moderna coronavirus vaccines, both of which are in use in Finland, also protect unvaccinated family members. The study examined the connections between these mRNA coronavirus vaccines and the infection risk among health care employees that were vaccinated in January-March, and their unvaccinated family members. 

‘Our study shows quite clearly that the vaccines also protect unvaccinated adults living in the same household. The results support the observation that vaccines reduce the risk of being infected and infecting others, while preventing further infections. However, it is difficult to evaluate the proportion of further infections that the vaccine would prevent. Only some of the infections come from people living in the same household,’ says Mika Kortelainen, Professor of Health Economics at the University of Turku.

‘Evaluating the indirect protective effect of vaccines in extensive vaccine programmes is methodologically one of the most difficult research questions related to coronavirus vaccines.  We have succeeded in partially answering this question by merging the materials of several Finnish registers,’ says the head of the research group, Academy Research Fellow Lauri Sääksvuori of the Finnish Institute for Health and Welfare and the University of Turku.

The study focuses on health care personnel, because this group included a significant number of households in which only one person had been vaccinated against coronavirus in January-March.

Coronavirus vaccine coverage is growing rapidly in Finland and around the world. The rise in vaccine coverage is expected to enable a controlled opening of society. The fresh study provides new information on how vaccines affect infections among the unvaccinated, thereby offering additional information for decision-making on dismantling restrictions.

‘Henceforth we also plan to evaluate the protective effect that adults who have been vaccinated against coronavirus might have on children in the family,’ says doctoral candidate Jussipekka Salo of the University of Helsinki.

The publication has not yet been peer-reviewed. The study is based on work conducted by the health economics group of the Helsinki GSE Situation Room. Implementation of the study has been supported by researchers of THL’s Infectious Diseases and Vaccinations Unit.

The study is available here: https://www.medrxiv.org/content/10.1101/2021.05.27.21257896v1

Further information:
Lauri Sääksvuori
+ 358 29 5247546
lauri.saaksvuori@thl.fi

Mika Kortelainen
+358 50 308 2642
mika.kortelainen@utu.fi

Helsinki Graduate School of Economics is a joint teaching and research unit in economics of Aalto University, University of Helsinki and Hanken School of Economics.