If a third dose of vaccine is the best weapon we have against the Omicron variant, it is not miraculous either, warn experts consulted by Press, who urge Quebecers not to lower their guard.
A study released Wednesday, co-signed by renowned researchers at Columbia University but not yet scrutinized by peer review, reports a “striking” vaccine escape of the Omicron variant in the face of antibodies.
“It’s a little disturbing,” notes Alain Lamarre, professor and researcher specializing in immunology, virology and cancer at the National Institute for Scientific Research.
“It indicates that the antibodies are very affected in their ability to neutralize the virus against Omicron and that even with a third dose, it does not go back to the initial level,” he explains.
Faced with Omicron, “the booster doses will not make you as protected as what you had against the Delta variant”, indicates Benoit Barbeau, virologist and professor in the department of biological sciences at the University of Quebec in Montreal.
“I think it’s a good idea to put into perspective that a third dose will not be miraculous,” notes Andrés Finzi, immunologist at the University of Montreal.
This “striking” finding should be put in context, however, the researchers point out.
“Protection is much more complex than the ability of these antibodies to neutralize the virus in a test tube,” recalls Mr. Lamarre.
“In one person, it’s still quite different. There are not only the antibodies, there are other elements in the immune response, there are the cells, the cellular components ”, abounds Mr. Barbeau.
It will be necessary to see “in real life”, in other countries where the administration of the third dose is more advanced, predicts Mr. Lamarre.
The third dose won’t have a dramatic effect, but it should be strong enough to give you better ability to fight infection. So it’s far from being a sword in the water.
Benoit Barbeau, virologist and professor in the department of biological sciences at the University of Quebec in Montreal
“A third booster dose may not protect you adequately from an Omicron infection, but of course, it is advisable to receive it”, write the authors of the American study.
Third dose needed
If two doses protected 95% against hospitalizations and 75% against infections in the case of the Delta variant, this is no longer true in the case of Omicron, insists the pediatrician and microbiologist-infectious disease specialist Caroline Quach-Thanh, of the CHU Sainte-Justine. “Two doses is 40% protection against infections and around 70% protection against hospitalizations. The booster dose increases this protection. ”
However, it is absolutely necessary to limit infections, she pleads, not without emotion.
If we have a lot of people infected with the same percentage of complications [qu’auparavant], hospitals will overflow. But our health network is no longer capable, it has been running at full speed for 22 months, people are exhausted!
Caroline Quach-Thanh, pediatrician and microbiologist-infectious disease specialist at CHU Sainte-Justine
The third dose did not show any particular risk. “The safety profile is roughly similar compared to the second dose. In Israel, the risk of myocarditis is rather similar to the risk after a first dose, that is to say lower, ”says DD Quach-Thanh.
For adults only
The accelerated third dose campaign announced by Quebec on Thursday is aimed only at adults. “We would not go straight away, before having safety data, offer the third dose for the youngest”, underlines the pediatrician.
The pharmaceutical company Pfizer, however, announced on Friday that it wanted to test a third dose of its vaccine in children from 6 months to less than 5 years, also reports Agence France-Presse. Pfizer also says it has started trials of a booster dose in 600 adolescents aged 12 to 17.
Deceptive feeling
Faced with the Omicron variant, “even with three doses, one should not have an overly strong feeling of security,” warns Mr. Lamarre, insisting on the importance of maintaining barrier measures and avoiding contact as much as possible.
Masks, but also ventilation and air purification systems and rapid tests, as well as antivirals when they are available, must also be part of the arsenal, adds Mr. Barbeau.
“We cannot vaccinate the entire population every three months because there is a new variant,” he said, referring to the challenges of logistics, costs and efficiency.
The scenario “which is highly probable and, I would say, hoped for as quickly as possible so that we finally go from a pandemic to an endemic” would rather be an annual dose, possibly combined with the influenza vaccine “and reflecting a little the variants in circulation, ”he explains.