COVID-19 vaccines provide strong protection against re-infection
COVID-19 vaccines provide strong protection against re-infection

COVID-19 vaccines provide strong protection against re-infection

COVID-19 vaccination provides lasting protection against re-infection, according to two studies published Wednesday in New England Journal of Medicine.

IN a studyreceive at least one dose of Pfizer vaccine after recovering COVID-19 was associated with a significantly lower risk of re-infection. Vaccine efficacy was 82% for ages 16-64 and 60% for ages 65 and older.

The data that was collected during the wave of Delta variant in Israel, “supports a public health policy of vaccinating patients who have recovered from COVID-19, especially in places where the Delta variant is still a cause for concern,” the study authors wrote.

Researchers from Clalit Health Services in Tel Aviv, Israel, analyzed electronic health records of more than 83,000 people who received at least one dose of the Pfizer vaccine after recovering from a previous coronavirus infection, as well as nearly 66,000 unvaccinated people who recovered. after a previous infection.

Re-infection occurred in 354 of the 83,356 vaccinated participants, or about 0.4%, and in 2,168 of the 65,676 unvaccinated participants, or 3.3%.

Among 65-year-olds and older, re-infection occurred in 28 out of 9,384 vaccinated participants, or about 0.3%, and 48 out of 4,799 unvaccinated participants, or 1%. The differences for the older age group may mean that older COVID-19 survivors may take more precautions against re-infection after recovering from the first infection, the study authors wrote.

In a separate analysis, the researchers found that the efficacy of the vaccine against re-infection was approximately the same for those who received one vaccine dose and those who received two vaccine doses after infection.

“Given the previous exposure to the virus, it appears that the primary vaccine dose in recovered patients produced a more robust and longer immunogenic response than the first dose alone in patients without previous COVID-19,” the study authors wrote.

In it second study, researchers at the UK Health Safety Agency evaluated the efficacy and duration of COVID-19 vaccination among healthcare professionals in the UK, including some who previously had an infection. They underwent tests for infection every two weeks, as well as monthly antibody testing.

The research team looked at infections among unvaccinated participants and those who received the Pfizer or AstraZeneca University of Oxford vaccine up to 10 months before.

Among 35,768 participants, 27% had recovered from COVID-19 and had antibodies. About 95% received two vaccine doses, with 87% receiving the Pfizer vaccine and 8% receiving the AstraZeneca vaccine.

Between December 2020 and September 2021, the group had 2,747 initial infections and 210 re-infections. Among those who had never been infected in the Pfizer group, vaccine efficacy was 85% between two and 10 weeks after the second dose, which dropped to 51% after about six months. In particular, the decline in protection occurred during the rise in the Delta variant in the UK, the study authors wrote.

Among AstraZeneca recipients, vaccine efficacy was around 58% between two and 10 weeks after the second dose, which did not decrease significantly over extended periods. Infection-acquired immunity decreased after one year in unvaccinated participants.

At the same time, vaccine efficacy remained higher than 90% for those vaccinated after infection, even among those infected more than 18 months before.

“Strategic use of booster doses of vaccine to avoid diminishing protection (especially in double-vaccinated, previously infected individuals) may reduce infection and transmission in the ongoing response to COVID-19,” the study authors concluded.

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