A study published on Monday concludes that vaccinated people who mix with those who are not have a significantly higher risk of being infected than those who mix with people who have received the vaccine.
In contrast, the risk of contracting COVID-19 in unvaccinated people decreases when they spend time with vaccinated people, because they serve as a buffer for transmission, according to the mathematical model used in the study published in the journal. of the Canadian Medical Association.
The main message of the study, according to its co-author, David Fisman, of the University of Toronto’s Dalla Lana School of Public Health, is that the choice to get vaccinated cannot be seen as simply personal.
“You might like to drive your car at 200 kilometers an hour and think it’s fun, but we don’t allow you to do that on a highway partly because you can kill yourself and hurt yourself, but also because you create a risk for those around you,” he said in a recent interview.
Mr Fisman said the idea for the study came a few months ago amid the debate over vaccine passports and vaccination requirements.
According to him, it is appropriate to conclude that public health involves actions that really need to be taken collectively.
The researchers used a mathematical model to estimate the number of infections that would occur in a population, based on the degree of interactions between vaccinated and unvaccinated people. They found that when people mixed with people with similar vaccination status, infection rates among those vaccinated decreased by 15% to 10%, but increased by 62% to 79% among those who were vaccinated. not vaccinated.
David Fisman said that in real life, people tend to spend more time with people who look like them. So, he said, even though 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 received vaccines. ‘injection.
He said the arrival of more contagious variants of COVID-19, such as Omicron, has impacted both vaccine effectiveness and public confidence in vaccination. But he said that even when the vaccine’s effectiveness was lowered to 40% in the model and the reproduction rate was increased to account for a more contagious variant, the general conclusions were the same.
He added that the study actually downplayed the importance of vaccines because it failed to take into account how they dramatically reduce the risk of death and hospitalization.
The results of the study, according to David Fisman, justify the implementation of public health measures such as vaccine passports and vaccination obligations. However, he acknowledges that a simple mathematical model does not fully reflect the real world or the various factors that must be considered when setting public health policy, including political considerations and public anger. .