Parents who are fully vaccinated and also boosted against Covid-19 may protect their unvaccinated children from the disease, suggests new research from Israel, published in Science.¹

Households with two parents, unvaccinated children and no history of previous Covid-19 infection were included in the study. Two periods of the pandemic were assessed; one, from January 17, 2021, through March 28, 2021, in children <16 years old when the Alpha variant was dominant (two doses vs no vaccination) and second, from July 11, 2021, through September 30, 2021, in children younger than 11 years when the Delta variant was the predominant strain (parents with booster dose vs those with only two vaccine doses). All vaccinated parents had taken at least two doses of the Pfizer mRNA Covid-19 vaccine.

Data from 400,733 unvaccinated children and adolescents in 155,305 separate households was examined during the first period of the study. While for the second part of the study, data from 181,307 unvaccinated children from 76,621 separate households was analyzed.

Having one fully vaccinated parent reduced the risk for infection with the original SARS-CoV-2 strain in children by 26%. Having two fully vaccinated parents reduced this risk by nearly 72%. In the second period of the study, having one fully vaccinated parent, including a booster dose, reduced the risk for infection with the Delta variant in children by 20.8%, and having two fully vaccinated parents was associated with a 58.1% reduced risk of infection in children.

SARS-CoV-2 transmission is common in households and unvaccinated members of the family including children are vulnerable to the infection. This study demonstrates that parental Covid-19 vaccination not only directly protects the parents themselves, it also indirectly protects the unvaccinated children in the household against alpha and delta variants. It further highlights that the protective effect was considerably more when both parents were vaccinated compared to single vaccinated parents during both periods of the study. This protective effect was independent of the age of the child or the number of people living in the same household.

Since this study was conducted before the Omicron variant was identified, the vaccine effectiveness against Omicron was not evaluated.

Reference

1. Hayek S, et al. Indirect protection of children from SARS-CoV-2 infection through parental vaccination. Science. 2022 Jan 27:eabm3087. doi: 10.1126/science.abm3087