s: Figures indicate that the AstraZeneca vaccine is less effective than the messenger RNA vaccines. Are there any plans for people vaccinated with AstraZeneca to be able to receive a third dose to increase their protection?
Elise Boudrette
R: Before talking about a possible third dose, let’s look at the data on the effectiveness of the vaccine. Is it true that the AstraZeneca (AZ) vaccine is less effective than the mRNA vaccine? It all depends on what numbers we’re talking about, emphasizes Alain Lamarie, professor in the Jane and Jean-Louis Lovesk Chair for Immunology Research at the National Institute for Scientific Research. “If we take the data on infections and diagnoses combined, it’s true,” he asserts. But it depends on when you take the test. If it is immediately after the vaccine, the two types of vaccine are equally effective. Second, the efficacy of AZ declines faster than that of the messenger RNA vaccine. In the face of delta variant infection – which accounts for the vast majority of cases of COVID-19 at the moment – it is estimated that the protection rate of the AZ vaccine is 50-60% while vaccines with Messenger RNA protect 80-90%. But after six months, the effectiveness of the two vaccines was again the same against infections. As for the interval between the two doses, extending the period to 10 or 12 weeks instead of 8 weeks has little effect. ”
On the other hand, if we are talking about the prevention of hospitalization and mortality, the two types of vaccine are equally effective.
Now let’s talk about a possible third dose. At the moment, according to Alain Lamarie, only immunocompromised persons are entitled to it.
“For those who have received the AZ vaccine, that is, people between the ages of approximately 45 and 65 years, the question of the third dose will come up around February. At that time, they will probably risk getting a dose of the Pfizer vaccine,” notes Alan Lamarie.
So let’s recap: If you receive the Pfizer or Moderna vaccine you are approximately 80-90% protected from infection with one of the Delta variants, but if you receive two doses of the AZ vaccine you are 50-60% protected. We therefore recommend that you remain vigilant, avoid direct contact with unvaccinated people, wear a mask and observe applicable health regulations.