MAINTENANCE. “In the case of an infection with Omicron, protection without vaccination is not sufficient”

“I got all my vaccinations. The last (reminder) on December 1st, 2021. On December 10th I tested positive for Covid-19. Should I consider this the fourth dose? »asks Francois.

In fact, according to the latest recommendations from the Ministry of Health, a Covid-19 infection corresponds to a vaccination shot. However, it all depends on when you got infected: more than three months after your booster shot or less than three months.

“If infection has occurred more than three months after the first booster, a second booster is not required. In fact, the occurrence of an infectious episode elicits an immune response at least equivalent to that of a booster dose.we read on the website of the Ministry of Health.

and “If infection has occurred less than 3 months after the first booster, a second booster is required. Then it is advisable to wait at least 3 months after infection for people aged 80 years and older, residents of nursing homes and USLDs or 6 months after infection for people aged 60 to 79 years with the second booster vaccination ».

So in your case, François, your infection does not mean a new dose of vaccine because it occurred too soon after your booster was injected, namely ten days later.

Also read: Covid19. Is the fourth dose mandatory? We answer you

To go further and understand if an infection corresponds to a dose of vaccine, we asked Yannick Simonin, virologist and research professor at the University of Montpellier. Maintenance.

Antibodies against Spike

What happens in the body during a vaccination or an infection?

If you are vaccinated or infected against Covid-19, the first reaction is a humoral reaction. After a few days, the body then produces antibodies that block the virus from entering. Then a few weeks later there is the immune response, which is a memory response. The cells prepare to respond again in the event of infection.

In the case of Covid-19, RNA vaccines are effective because they stimulate both types of responses. There are vaccines that only stimulate the humoral response, this is the case with inactivated vaccines, for example, and hence probably the Sinovac vaccine. But in most cases in Europe we have this double stimulation with the vaccines used.

What about the quality of the immune response, be it an infection or a vaccination?

There are actually different immune responses. With a vaccination, the antibodies are directed against the spike protein, while with a Covid infection, the body develops antibodies that are also directed against other proteins of the virus.

When vaccinated, the antibodies developed are more numerous and more effective against Spike, after infection, the antibodies also go against other parts of the virus, which can be compared to a dilution of the immune system. It’s not just fighting the spike protein.

Also read: Covid19. I got infected after my third dose, am I well protected?

With Omicron, being infected but not vaccinated is not sufficient protection.

—Yannick Simonin

When is one best protected?

For the Omicron variant, the data suggest that one is better protected after vaccination than after infection. Very often we are better protected in the event of an infection, but vaccination would be more effective with this variant.

The best protection is vaccination, two doses, followed by infection. There, the antibodies are more important and more stable over time. Both doses of the vaccine reduce the intensity of the symptoms.

Two doses or three doses followed by infection is where the best stimulation is achieved. With Omicron, being infected but not vaccinated is not sufficient protection.

Also read: Covid19. Incubation, risk of infection, symptoms: What have the Omicron variants changed?

How many months protected?

So is this in line with the Ministry of Health’s vaccination recommendations? The ministry explains that in some cases, infection can replace a booster shot.

Yes that’s it. But a person who is only infected, who has not been vaccinated, cannot be considered vaccinated.

What is the knowledge about the duration of protection of vaccines?

Protection against symptomatic forms is estimated at 4-5 months after the vaccination dose, then it weakens, but protection against severe forms is still there, at around 80%.

Hence a fourth dose for the over 60s, allowing an increase in the level of protection. There may be an incentive for a booster vaccination in the general population at the start of the school year in September, but this depends on the variants circulating at that time.

Also read: Covid19. A sharp drop in the cases observed in France: what can we expect for this summer?

We are heading for a period of calm in the coming months. We have a Swimming pool Immune reactions in the population: people who are fully vaccinated, people who were then vaccinated, people who were infected with different variants… But a person who was never vaccinated and infected with Omicron will only have weak protection.

MAINTENANCE. “In the case of an infection with Omicron, protection without vaccination is not sufficient”

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