Photo: The Canadian Press
Vaccine passport protest in Vancouver last year.
While staying unvaccinated against COVID-19 is often presented as a personal choice, those who reject vaccines increase the risk of infection for people around them, a new study shows.
A study published Monday in the Canadian Medical Association Journal found that vaccinated people who mingle with those who were not vaccinated were significantly more likely to be infected than those who clung to people who received the vaccine.
In contrast, the risk of COVID-19 infection in unvaccinated people is reduced when spending time with people who have been vaccinated, as they serve as a transmission buffer, according to the mathematical model used in the study.
Co-author David Fisman of the University of Toronto’s Dala Lana School of Public Health said the study’s message was that the choice to vaccinate could not be seen as personal.
“You may want to drive 200 kilometers an hour and think it’s fun, but we don’t allow you to do it on the highway, partly because you can kill yourself and get hurt, but also because you put others at risk.” he said in a recent interview.
Fissman said the idea for the study came a few months ago amid a debate over vaccine passports and vaccine mandates.
“We thought what was missing in this conversation was what are the rights of vaccinated people to be protected from unvaccinated people?” He said.
The conclusion, he said, was that “public health is something you really have to do collectively.”
“What we’ve come to, to some extent, is that the decision not to get vaccinated – you can’t really see it as a risk to yourself (because) you’re risking it for other people around you by interacting with them,” he said.
The researchers used a mathematical model to estimate how many infections will occur in the population, depending on how much mixing has occurred between vaccinated and unvaccinated people. It has been found that when people mix with people with a similar vaccination status, the infection rate among vaccinated people decreases from 15 percent to 10 percent and increases from 62 percent to 79 percent among those who are not vaccinated.
Fissman said that in real life, people tend to spend the most time with people who are like them. So, he said, even if vaccinated people are more likely to spend time with others who have received vaccines, they are disproportionately affected when they spend time with those who have not.
He said the arrival of more contagious variants of COVID-19, such as Omicron, has affected both the effectiveness of the vaccine and public belief in vaccination. But he said that even when the vaccine’s effectiveness was reduced to 40 percent in the model and the reproductive rate was increased to account for a more contagious variant, the general conclusions were the same.
He said the study actually underestimated the importance of vaccines because it did not take into account how they significantly reduced the chances of death and hospitalization.
Fissman said the results, from a purely “utilitarian” point of view, provide a rationale for implementing public health measures such as vaccine passports and vaccine mandates.
However, he acknowledges that a simple mathematical model does not fully reflect the real world or the various factors that need to be taken into account when defining public health policy, including political considerations and public anger.
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