Indirect protection of children from SARS-CoV-2 infection through parental vaccination

Children not vaccinated against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may still benefit from vaccines through protection from vaccinated contacts. We estimated the protection provided to children through parental vaccination with the BNT162b2 vaccine. We studied households without prior infection consisting of two parents and unvaccinated children, estimating the effect of parental vaccination on the risk of infection for unvaccinated children. We studied two periods separately—an early period (17 January 2021 to 28 March 2021; Alpha variant, two doses versus no vaccination) and a late period (11 July 2021 to 30 September 2021; Delta variant, booster dose versus two vaccine doses). We found that having a single vaccinated parent was associated with a 26.0 and a 20.8% decreased risk in the early and late periods, respectively, and having two vaccinated parents was associated with a 71.7 and a 58.1% decreased risk, respectively. Thus, parental vaccination confers substantial protection on unvaccinated children in the household. Description Protection, whether direct or not Vaccination provides both direct protection of vaccinated individuals and indirect protection of individuals living in vaccinated communities. Two studies based on data from Israel investigated the efficacy and indirect protection of the Pfizer/BioNTech messenger RNA vaccine (see the Perspective by Dean and Halloran). Prunas et al. used statistical approaches to analyze transmission in households from June 2020 to July 2021. People who were vaccinated and subsequently infected were less infectious than unvaccinated persons. Moreover, less transmission occurred within households with vaccinated members than in those with unvaccinated individuals. However, the ability of the vaccine to prevent transmission waned with time and with the advent of the Delta variant. Hayek et al. investigated whether older and vaccinated household members reduced the risk of infection to younger children who are as yet ineligible for vaccination. Regardless of household size, parental vaccination substantially reduced the risk of children up to 12 years old becoming infected. This indirect effect will protect children from risk of severe disease and reduce the propagation of transmission chains. —CA Parental Covid-19 vaccination confers substantial protection for unvaccinated children in the household.