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Vaccinated people infected with Omicron have four times the protection: study


According to a study, vaccinated people who were infected with the first subvariants of Omicron have four times the protection of people who were bitten and who did not catch the Covid-19 infection.

The research, published recently in the New England Journal of Medicine, analyzed the likelihood of vaccinated people being infected with the currently circulating BA.5 subvariant.

Researchers in Portugal estimated the degree of protection conferred by infections with previous variants and used real-world data.

“Vaccinated individuals who have been infected with Omicron subvariants BA.1 and BA.2 have approximately four times the protection against infection with subvariant BA.5, which has been circulating since June, than vaccinated people who have not been infected at any time,” said Luis Graca, a professor at the University of Lisbon.

“Infections in 2020 and 2021 that occurred by infection with earlier variants of the SARS-CoV-2 virus also confer protection against infection for the newer Omicron variant, although this protection is not as high as that of people infected with BA.1 and BA.2 variants, early 2022,” said study co-lead Grace.

These results are very important because the adapted vaccines that are in clinical development and evaluation are based on the BA.1 subvariant of the virus, which was a dominant variant in infections in January and February 2022, the researchers said.

Until now, it was unclear what degree of protection this subvariant offers against the currently circulating strain, they said.

The researchers had access to the register of Covid-19 cases at the national level of Portugal.

“We used the Portuguese National Registry of Covid-19 Cases to obtain information on all cases of SARS-CoV-2 infections in the population over 12 years old residing in Portugal,” said Manuel Carmo Gomes. , associate professor at the University of Lisbon. .

“The viral variant of each infection was determined by taking into account the date of infection and the dominant variant at that time. Together we looked at infections caused by early variants of Omicron BA.1 and BA.2,” Gomes said.

The researchers then analyzed the probability that a previously infected person would be reinfected with the current variant, which allowed them to calculate the percentage of protection provided by previous infections.

The study demonstrates that prior infection in vaccinated individuals continues to confer for variants known to evade the immune response, such as the currently dominant subvariant, they added.


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