A new study suggests that while remaining unvaccinated against COVID-19 is often framed as a personal choice, those who spurn the vaccines raise the risk of infection for those around them.

The study is published today in the Canadian Medical Association Journal.

It says vaccinated people who mix with the unvaccinated have a significantly greater chance of being infected than those who stick with people who’ve received the shot.

In contrast, unvaccinated people’s risk of contracting COVID-19 drops when they spend time with vaccinated people because they serve as a buffer to transmission.

Co-author David Fisman, of the University of Toronto’s Dalla Lana school of public health, says the message is that the choice to get vaccinated can’t be thought of as merely personal.

The researchers used a mathematical model to estimate how many infections would occur in a population, depending on how much mixing occurred between vaccinated and unvaccinated people.

However, Fisman acknowledges that a simple mathematical model doesn’t fully reflect the real world or the diverse factors that must be taken into account when setting public health policy, including political considerations and public anger.