COVID: 3 things to watch out for this winter

The variable of immunity

Whatever the country, the vaccination rate is known: for example, 79.7% in Quebec as of November 19 against 76.4% in France. However, one piece of data is unknown: how many people have had COVID? We may have a total number of cases, it partly overlaps with the vaccinated and therefore tells us nothing of all those who now have antibodies in them.

As journalist Sarah Zhang writes in the magazine The Atlantic, “This uncertainty is important because even a small percentage can translate into a large number of people” likely to be infected, therefore hospitalized. And because the unvaccinated tend to be people who share affinities, or are more numerous in certain neighborhoods or regions, the risk of new outbreaks is therefore greater than if they were evenly distributed throughout the population.

This is what is currently being observed in several European countries, such as Germany, where the vaccination rate is slightly below 70%. This country announced, last Thursday, restrictions to the unvaccinated in their access to public places.

In addition, there is the possibility that the immunity induced by infection or by the vaccine may decline over time.

The variant variable

In one year, Sarah Zhang recalls, between the Alpha and Delta variants, the virus has doubled its contagion rate. This “evolution” seems to have slowed down in recent months, without knowing whether it can be attributed to vaccination. But it remains a risk nonetheless: a variant which, through the mutations that the virus continues to undergo, would find the “recipe” to escape our immunity, would have an immense playing field at its disposal. It would not bring us back to square one, because our immune system would not be entirely helpless in the face of this close cousin of a virus that it already knows; but statistically, it would cause more re-infections or new infections.

The human factor

Some of the above will also depend on our behavior this winter. “The coronavirus does not jump on planes, cross borders, or make it to holiday season,” Zhang writes. We are doing it. And that’s why the human factor has always been, in epidemiology, the most difficult part of the equation to predict.

It plays in the good way as in the bad way: if the new school year did not cause the new wave that we feared, it is probably because we have become more careful, with our masks and our social distancing. There were also areas in the United States that were still very resistant to vaccination this summer, but where the vaccine rate increased in early fall. In Quebec, a warmer fall played in favor of the human factor: meetings outside were less risky. The arrival of winter will be the real test.

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