As the administration of the booster dose of COVID-19 vaccines accelerates in Quebec, several questions are emerging, in particular as to its effectiveness against the Omicron variant, now dominant in the province. Experts take stock.
Why is the booster dose needed?
Initially reserved for people aged 70 and over, access to the booster dose has gradually widened in recent weeks to include people aged 60 and over, healthcare workers and, since Wednesday, several “Priority clients” working in different sectors of the economy. At this rate, by March, “the entire population” of adult age in the province could have received its booster dose, Health Minister Christian Dubé said on Tuesday.
This vaccination effort comes as cases of COVID-19 and related hospitalizations have continued to climb at a frantic rate in Quebec in recent days. However, the Omicron variant of COVID-19, which has quickly established itself in the province since its discovery in South Africa in November, shows some resistance to COVID-19 vaccines.
According to various experts and preliminary studies carried out in the United Kingdom, among others, the protection offered by two doses of the vaccine against infection with this variant would be around 30%. The booster dose, however, would increase this percentage to around 75%. The protection provided by this third dose against serious symptoms leading to hospitalizations could also amount to 85%, notes the immunologist at the Montreal Clinical Research Institute André Veillette, in an interview with the Duty Wednesday.
Thus, the booster dose could help reduce community transmission as well as the pressure on the hospital network, which is at the end of its rope, by helping to flatten the epidemiological curve in the province.
“It will help protect the population against hospitalizations. And we know that the health care system is currently under pressure, to such an extent that we are asking workers [atteints par la COVID-19 mais] asymptomatic from working, ”notes Roxane Borgès da Silva, professor at the School of Public Health at the University of Montreal.
The downside is that with the Omicron variant, “people are wondering how long the increase in protection with the third dose will last,” says Veillette, however.
In this regard, the microbiologist-infectious disease specialist at the Center hospitalier universitaire de Sainte-Justine Caroline Quach-Thanh notes that recent British research suggests that the effectiveness of the third dose on the prevention of infections would drop from 75 to 50% in a period of ten weeks after his injection. “We still have the impression that [la dose de rappel] will prevent more severe infections, ”she says.
Is the third dose relevant for people who have contracted COVID-19 in addition to being vaccinated twice?
The Legault government continues to mention on its website that, for people who have contracted COVID-19, a single injection is enough to protect themselves from the virus. They can, however, get two more doses if they wish.
“For anyone who has had COVID and two doses of the vaccine, there is no recommendation to go get the third dose because COVID infection and two doses offer stronger protection than three doses” , explains Caroline Quach-Thanh. In this context, “we must reserve the third dose for people who need it most”, and therefore to people who have not contracted COVID-19 in recent months, opines the professor at the Department of Biological Sciences of the ‘UQAM and virology expert Benoit Barbeau.
André Veillette believes for his part that “we should not count a case of COVID-19 as a vaccine”, since the immunity provided by an infection decreases over time and varies according to the intensity of the symptoms felt during that period. -this.
“Especially since with Omicron, there are a lot of very mild illnesses. That means that there may not be a lot of antibodies that are induced by that, ”notes the expert. So, “it’s not clear if an infection counts for immunization,” he says. The expert believes that all eligible people should get their booster dose, whether or not they have contracted COVID-19 in recent months.
Should we fear the side effects of the booster dose?
Earlier this winter, seniors in CHSLDs over the age of 70 who had already contracted COVID-19 suffered significant side effects after receiving their booster dose, which then caused a stir. However, these people had received a dose of the vaccine twice as high as that currently recommended by the Quebec government. “It turned out to be a bad idea,” raises Mr. Veillette, who fears that this event will make some people reluctant to request a third dose of the COVID-19 vaccine.
However, for the vast majority of the population, the side effects associated with this third dose will be just as minor as during the first two injections, according to the experts consulted by The duty Wednesday. “We should not expect side effects greater than what we had before”, assures in particular Benoit Barbeau.
Does the booster dose vaccination campaign come too late to combat the Omicron variant?
In recent days, new COVID-19 contaminations have declined in South Africa, where the Omicron variant was first reported. Projections released earlier this month by the National Institute of Public Health of Quebec also suggested that a peak in hospitalizations and positive cases identified could be reached in February, after which the epidemiological curve would drop quickly.
However, the booster dose remains relevant, even for young people who will receive it late, given the schedule put in place by Quebec, believes Benoit Barbeau.
“We must give this protection as quickly as possible, because we do not know the duration of this new wave in Quebec,” notes the expert, who emphasizes that it is difficult to predict whether the epidemiological curve in Quebec may or may not follow a trend similar to that of South Africa in the coming weeks.
” It’s never too late [pour obtenir sa dose de rappel] because the variant will continue to circulate, and before it contaminates the entire population of Quebec, it will take several weeks or several months ”, also notes Mr.me Borges da Silva.
Should I reschedule my appointment for a third dose if I contract COVID-19?
A person who contracts COVID-19 should make sure that their appointment at a vaccination center is at least eight weeks after they are diagnosed positive for the disease. Otherwise, she will have to postpone her appointment. “They don’t want to see you at the vaccination center if you have the virus,” recalls André Veillette.
A person who now contracts COVID-19 would also benefit from canceling their appointment for the booster dose and taking it at a later date, since the vaccines offered may have been improved in the meantime to better respond to new variants of the virus, notes Caroline Quach-Thanh.