The sixth wave of COVID-19 generated by the BA.2 subvariant is the first since the start of the pandemic to have been little influenced by health measures and to have followed a “natural” curve.
This is at least what the National Institute of Public Health of Quebec observes, after having gone through six waves, punctuated by various restrictions and population measures intended to “flatten the curve” and influence the course of the pandemic.
According to the Dr Gaston De Serres, medical adviser at the INSPQ, everything contributes to demonstrating that the latest health measures still in place in April and May, apart from access to vaccination, had little effect on the trajectory of the sixth wave. .
This is why the INSPQ expects very limited effects from the recent lifting of mask wearing on the current downward trend in cases and hospitalizations.
“The curve of infections started to drop long before mask-wearing was abandoned. This is the first wave that evolves naturally because the virus is so contagious that it meets more and more individuals, and it continues its course, regardless of health measures, ”says Gaston De Serres.
And this because the wearing of the mask, limited to a few public places, was not enough to stem the sustained transmission of the virus.
“The transmission was mainly intrafamilial, generated by children, or by private visits and gatherings, where there were no masks required. The number of situations where the mask was still compulsory was too limited to have a major impact, ”adds the latter.
The Dr De Serres underlines the very large difference in contagiousness between the various variants that marked the first waves of the pandemic and the most recent ones. “The BA.1 and BA.2 subvariants are three times more contagious, so places that were once non-problematic for transmission are now. This is why so many people have been infected. But the immunity acquired by the very large number of recent infections and by vaccines seems to have created a barrier which caused the virus to naturally recede. [lors de la sixième vague]. It is not going to disappear, but it has fallen in a natural way, ”he explains, in particular due to the warming of temperatures.
In previous waves, public health measures had “strangled” the virus by forcing a decline in social contact, notes this researcher. Although less contagious, several of the previous variants caused more severe symptoms. “And it worked to protect our healthcare system. It created an artificial decrease, by the drop in contacts, ”he says.
At this time, contacts between citizens have resumed a normal course, as evidenced by the influenza epidemic which is in full swing, also fueled by the return of activities between humans. But this recent recovery has hardly influenced the number of hospitalizations for the moment which, like the cases, continues to decline, adds this medical adviser to the INSPQ.
On the other hand, the rise of new highly contagious sub-variants (BA.2.12.1 in the United States and BA.4 and BA.5 in Europe), which give health authorities a hard time, could change the situation. In New England, the predominance of the 2.12.1 subvariant prompted the mayor of New York this week to place his city on “high alert”. With a 24% increase in hospitalizations in two weeks, the Centers for Disease Control and Prevention (CDC) has just recommended again to a third of Americans living in states with high transmission to wear masks in public places. interiors.
Some observers fear that the wave in the United States will be worse than previous ones, as these new subvariants may escape immunity conferred by current vaccines and previous infection with BA.1 (first subvariant of Omicron). Because the BA.4, BA.5 and BA.2.12.1 descendants have specific mutations that increase this ability. Unless new vaccines that are more effective against reinfection emerge, such variants could challenge health systems and cause two peaks per year, despite widespread vaccination, advance some preliminary studies.
Effects on deaths
According to the Dr De Serres, it is now clear that COVID deaths and hospitalizations are now hitting more people who are triply vaccinated than before, even if the vaccines remain partially effective against severe forms of the disease.
“COVID will continue to hit vulnerable people and there are many in our population. Since the arrival of Omicron, the vaccines are no longer as effective in these people, as was the case with the previous variants,” he says.
This situation explains why hospitalizations involving COVID, despite the decline in cases of infections, continue to be numerous.
In this epidemiological context, Alain Lamarre, immunologist at the National Institute for Health Research (INRS), believes that giving up wearing a mask will continue to have harmful consequences for a whole class of people whose vaccine immunity is rapidly weakening. with time. “The bad news is that a significant number of deaths are likely to be part of our landscape for quite some time,” he said. A large pool of people who are quite sick are at risk of being exposed to the virus and continuing to die from it. »