4th dose of vaccine |  Take it now or wait until the fall?

4th dose of vaccine | Take it now or wait until the fall?

With the increase in cases throughout the province, should you take the fourth dose now or wait for the booster doses adapted to the new variants, scheduled for autumn? Experts help us see things more clearly.

Posted at 7:00 am

Alice Girard Bosse

Alice Girard Bosse
Press

“Healthy people who have taken their third dose are generally well protected. They can afford to wait a bit,” says Nathalie Grandvaux, a researcher at the Host Response to Viral Infections Research Laboratory at Montreal University Hospital Center (CHUM).

The DD Caroline Quach-Thanh, a professor in the faculty of microbiology, infectious disease and immunology at the University of Montreal, agrees. “A person who has already received three doses of the vaccine and an infection with Omicron remains approximately 90-95% protected. She could pick up the fourth dose from her in the fall,” she says.

However, people’s occupations can have an impact, says Ms.me Grandvaux. “If someone decides to take trips this summer or visit vulnerable people, it would be a good time to go look for it,” says the specialist.

In Quebec, people over 18 years of age can receive a fourth dose, or a second booster dose, three months or more after the previous one. People older than 12 years on dialysis or with weakened immune systems can also get it.

The experts are unanimous, however, when it comes to people over 60 and vulnerable people: they should take the fourth dose as soon as possible.

“With the increase in cases and the transmissibility of variants circulating, it’s good to go looking for it,” says Dr.D Chantal Sauvageau, medical adviser on infectious diseases at the National Institute of Public Health of Quebec (INSPQ).

During a press conference last week, the national director of public health, Dr.r Luc Boileau also invited people who are immunocompromised, people 60 years of age or older, and those with a chronic illness to get a fourth dose of the COVID-19 vaccine, if they haven’t already.

The arrival of new vaccines

All vaccines currently in circulation are based on the initial strain of the virus and have gradually proved less effective against variants that have emerged over time. Therefore, Moderna and Pfizer have developed specific booster doses for Omicron and its sub-variants that could be offered starting in the fall.

“We know that in Canada we will have six million doses, so there will not be for everyone,” specifies the DD Quach Thanh. These doses could be offered from the end of August depending on the decision of Health Canada, it indicates.

Should we wait for the arrival of booster doses adapted to Omicron? Not necessarily, experts say. “We were hoping that there would be no cases this summer, but there is an increase and it is only in early July. If it is indicated to get vaccinated now, I think we have to do it regardless of what happens in the fall,” said André Veillette, a professor at the University of Montreal School of Medicine.

A magic formula?

On June 22, Moderna claimed that its new COVID-19 booster vaccine candidate, which the company expects to see approved in the fall, was effective against Omicron’s latest sub-variants.

This new formula is a so-called “bivalent” vaccine, that is, it targets both the initial strain of the virus – like the vaccine administered so far in the world – and the Omicron variant.

This boost showed a greater than five-fold increase in neutralizing antibodies against the BA.4 and BA.5 subvariants. However, even these high levels were only a third of the levels achieved against the original Omicron strain, BA.1.

Experts warn, however, not to rejoice too quickly. “Is this small increase in antibodies magical? No, I don’t think so,” says D.D wild. The DD Quach Thanh second. “It’s a good vaccine, but to say it’s going to be a complete game changer, we’re not convinced,” he said.

For his part, the CEO of Moderna, Stéphane Bancel, announced that he was sending this data to the regulators “as a matter of urgency”. “We are preparing to deliver our next-generation bivalent booster starting in August, ahead of a possible surge in SARS-CoV-2 infections due to Omicron subvariants in early fall,” he said in a statement.

Pfizer-BioNTech is also testing an “updated” version of its vaccine specifically targeting Omicron. The alliance said it could move to production of such vaccines within three months.

With Agence France-Presse, The Associated Press and The Canadian Press


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