Non immune family members are at a lower risk of Covid-19 as the number of immune persons in the family increases, according to a new study from Sweden published in JAMA Internal Medicine.

Nearly 1.8 million persons from over 800,000 families (each family comprising 2-5 family members) were analysed. Data for the study was sourced from the Public Health Agency of Sweden, the National Board of Health and Welfare and Statistics Sweden. Individuals who had developed immunity following a previous natural infection or full immunization were included in the study. Each immune person was matched 1:1 to a nonimmune person in a family. The main outcome measure was the development of new Covid-19 infection in nonimmune family members from April 15 to May 26, 2021.

An inverse association was seen between the immune persons and the risk of infection in nonimmune family members. The risk of acquiring Covid-19 and subsequent hospitalization was 45-61% lower in nonimmune family members, which had one family member with immunity to Covid-19.

This protective effect of the vaccine increased with an increase in the number of immune family members. With two immune family members, the risk was reduced by 75-86%; with 3 immune family members, the decline in the risk was 91-94% and with four immune family members, the risk reduction was 97%.

Developing herd immunity via natural infection is not an option. Vaccination is the only way to quickly develop herd immunity and prevent emergence of new variants. For this, all eligible persons need to be immunised. India’s Covid-19 vaccination drive has picked up after some hiccups and is now moving at a good pace; more than 96 crore vaccine doses have been administered so far; 71% of the population has received the first dose of the vaccine, while 27% have received both doses.

This study recapitulates the benefits of immunization in curbing the spread of Covid-19 within the family and the community in addition to reducing the individual risk. Everyone must take both doses of the vaccine and at the same time, follow all standard precautionary measures.

Reference

1. Nordström P, et al. Association between risk of COVID-19 infection in nonimmune individuals and COVID-19 immunity in their family members. JAMA Intern Med. 2021 Oct 11. doi: 10.1001/jamainternmed.2021.5814. Online ahead of print.