People with “hybrid immunity” from having been both fully vaccinated and previously infected with Covid-19 have the strongest protection against the virus, two new studies announced on Friday.

After two years of a pandemic that has seen nearly 500 million people infected and billions vaccinated, studies have highlighted the importance of getting bitten for those with natural immunity after recovering from the disease, a said AFP.

One of two studies published in the medical journal The Lancet Infectious Diseases analyzed health data from more than 200,000 people in 2020 and 2021 in hard-hit Brazil, which has the second highest Covid death toll in the world. .

He revealed that for people who have already had Covid, vaccines from Pfizer and AstraZeneca offered 90% effectiveness against hospitalization and death, China’s CoronaVac had 81% and Johnson & Johnson’s one-shot jab had 58%.

“These four vaccines have been shown to provide significant additional protection to people previously infected with Covid-19,” said study author Julio Croda of the Federal University of Mato Grosso do Sul.

“Hybrid immunity due to exposure to natural infection and vaccination is likely to be the norm globally and could provide long-term protection even against emerging variants,” said Pramod Kumar Garg. from the Indian Institute of Translational Health Science and Technology in a comment related to the study.

A study using Sweden’s national registry up to October 2021 found that people who recovered from Covid retained a high level of protection against reinfection for up to 20 months.

And people with hybrid immunity to two doses of vaccine had a 66% lower risk of reinfection than those with only natural immunity.

Paul Hunter, a professor of medicine at the University of East Anglia who was not involved in the study, told AFP that the 20 months of “very good protection” against natural immunity was “much better than we expected for the two-dose original”. vaccination schedule.

But he warned that both studies were completed before the Omicron variant became dominant across the world, and that it had “significantly diminished the protective value of previous infection”.

A study in Qatar published on the preprint website medRxiv last week provided insight into the protection afforded by hybrid immunity against Omicron.

It found that three doses of the vaccine were 52% effective against symptomatic infection of the BA.2 Omicron subvariant – but that number rose to 77% when the patient had already been infected.

The study, which has not been peer-reviewed, found that “hybrid immunity resulting from prior infection and recent booster vaccination confers the strongest protection” against BA subvariants. .1 and BA.2.