Covid-19: does a triple vaccinated have as much risk of being contaminated by Omicron as by Delta?

The fifth wave never ends. Thursday, December 23, France recorded more than 91,000 new cases of Covid-19, unheard of in the country. An epidemic outbreak linked to the Delta variant – still very present even if the peak seems to have passed – associated with the Omicron variant, much more contagious and predominant “between Christmas and New Year”, according to government spokesperson Gabriel Attal.

To counter it, the executive always rejects the hypothesis of new restrictions, such as the closure of certain places (in addition to nightclubs), and prefers to bet on vaccination, in particular the booster dose. According to the latest data from Public Health France, this recall campaign, launched before the arrival of Omicron, has already enabled more than 21.7 million French people to receive their third injection. Does this allow them to avoid contamination linked to this variant? Is the protection as strong as against Delta? Philippe Amouyel, epidemiologist and professor of public health at Lille University Hospital, responds to LCI.

People vaccinated with the booster dose still seem to be contaminated with Covid-19. Is it due to the Omicron variant?

Yes. In the current context, if you are vaccinated with three doses, but positive for Covid-19, the infection is more likely to come from the Omicron variant than from the Delta. Vaccination protects better against Delta reinfection than against that caused by Omicron. Once you have received your booster dose, the risk of being re-infected with Delta is relatively low. For Omicron, full vaccination (with the booster dose) protects well against severe and symptomatic forms, but less against reinfection.

The third dose will therefore have no effect on the explosion of contamination by Omicron?

Yes. According to data in Denmark, people vaccinated with three doses are three times less likely to be infected with Omicron than those vaccinated with two doses. This shows that vaccination protects, even if this variant is somewhat more resistant to the vaccine than its predecessor.

Why ?

These are the differences in the forms of the Spike protein (which allows the virus to cling to the body, editor’s note) induced by the mutations that bring a little more resistance to vaccines. But make no mistake: in general, a vaccinee has less risk than an unvaccinated one of being infected with one of the two variants.