Vaccination after Covid-19 infection for better protection

With a national incidence rate of more than 1,400 new cases per 100,000 population over the past week, all eyes remain on the Covid-19 outbreak. Many people, although vaccinated, contract SARS-CoV-2. A few days ago, two new studies were published, suggesting better protection for people who receive vaccination after contracting the infection. Details.

Vaccination after Covid-19

According to the recommendations currently in force in France, the booster vaccination must be carried out three months after the second dose of vaccine. For people who have contracted Covid-19 during this three-month period, there is no obligation to carry out a vaccination booster. However, recall is required for entry into certain foreign countries and such persons may recall as early as three months after infection with SARS-CoV-2.

Numerous scientific studies have focused on the question of the protection conferred reciprocally by infection and by vaccination. More recently, a new question has arisen, that of the protection conferred by vaccination or booster vaccination after infection with SARS-CoV-2. A question that has been the subject of two recent studies, which come to the same conclusions.

Vaccination after infection leads to better protection against Covid-19

The first study had several objectives. On the one hand, it aimed to determine the duration of the protection conferred by infection with SARS-CoV-2. On the other hand, it investigated the interest of vaccination in infected people and the relative effectiveness of one vaccine dose compared to two. Researchers conducted in Israel on 149,032 patients infected with SARS-CoV-2 between March and November 2021.

Of the study participants, 56% were vaccinated with the vaccine distributed by Pfizer. The reinfection rate (i.e. the number of patients who were infected with the virus a second time) was:

  • 2.46 cases per 100,000 people per day among vaccinated participants;
  • 10.21 cases for unvaccinated participants.

Vaccine efficacy was 82% in subjects aged 16 to 64 years. On the other hand, it was only 60% among those over 65 years old. The data collected showed no significant difference between the one-dose and two-dose vaccine regimens. Thus, this study suggests that the administration of at least one dose of vaccine reduces the risk of reinfection after a first episode of Covid-19.

Protect yourself from a possible reinfection, sometimes severe

The second study aimed to assess the effectiveness of four vaccines against Covid-19. The researchers quantified the effectiveness of the vaccines according to several criteria. They measured their protection against reinfections, hospitalizations and the death of patients who presented a first infectious episode. Scientists conducted this study in Brazil between February 2020 and November 2021 on 213,457 infected people. Of the participants, 14.5% experienced reinfection with the virus.

The overall effectiveness of the four vaccines in people who had been infected ranged from 39.4 to 64.8%. The vaccine distributed by Pfizer had the highest efficacy. In addition, the administration of a complete vaccination schedule provided better protection than a single dose. Protection against hospitalization or risk of death varied from 81.3 to 89.7% depending on the vaccines. Thus, these data suggest that vaccination confers better protection against reinfection. Furthermore, vaccination protects against severe forms of Covid-19 in people already infected with SARS-CoV-2.

According to these two studies, post-infection vaccination is interesting to improve protection against Covid-19. A situation that concerns more and more French people!

Estelle B., Doctor of Pharmacy

Sources

– Efficacy of the BNT162b2 vaccine after recovery from Covid-19. nejm.org. Accessed April 6, 2022.
– Vaccination against Covid in France – as of April 3, 2022, 39,574,268 booster doses have been carried out. solidarites-sante.gouv.fr. Accessed April 6, 2022.
– Efficacy of CoronaVac, ChAdOx1 nCoV-19, BNT162b2 and Ad26.COV2.S in people with previous SARS-CoV-2 infection in Brazil: a test-negative case-control study. thelancet.com. Accessed April 6, 2022.

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