Protection is better after vaccine and infection, two studies reveal

Still not infected with Covid-19 after more than two years of the pandemic, do you think you are part of the “elite”, as we sometimes see on social networks? In reality, you may not be the best protected against the coronavirus. This prize goes, according to two studies published in the Lancet Infectious Diseases, to people who have been both vaccinated and infected.

The idea was to find out which, vaccination or infection, gave the best protection. The answer is not necessarily binary, but these studies underline that a former Covid patient has every interest in being vaccinated to strengthen the immunity already acquired by his past infection.

The risk of reinfection drops by 66%

The first of these works is based on the health data of more than 200,000 Brazilians, whose country has been one of the hardest hit in the world by the Covid pandemic. In this sample, some of the individuals were infected without being vaccinated. Among those who survived the disease, some received a vaccine – Pfizer/BioNTech, AstraZeneca, Sinovac or Johnson & Johnson/Janssen – and some did not.

However, “these four vaccines prove to give additional and substantial protection to people already infected with Covid-19 before”, remarks one of the authors, Julio Croda. This protection is more or less important: the risks of hospitalization or death are reduced by 90% with Pfizer/BioNTech and AstraZeneca, by around 80% with Sinovac, but only a little more than half with Johnson & Johnson.

The second study, carried out using Swedish data, goes in the same direction. It shows that former Covid patients retain high immunity for up to twenty months. But it also indicates that these people see the risk of reinfection drop even more – by two thirds, approximately – if they were vaccinated after their first infection.

However, these two studies have a weakness: they cover a period which precedes the emergence of the Omicron variant, which is clearly more contagious and resistant to vaccines than its predecessors. And which has infected many vaccinated people, sometimes even three times. However, they suggest that “hybrid immunity, acquired by being exposed to both infection and vaccination, (…) could give long-lasting protection, including against new variants”, estimates Indian researcher Pramod Kumar , who did not participate in these studies.

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