should people who have already been infected with the virus be vaccinated?

As vaccination campaigns are taking shape, priority population groups have been defined by health authorities. But the case of people who have already been carriers of the virus raises multiple questions: can their immunity exempt them from the vaccine? What effects can it have on them? Are their persistent symptoms compatible with vaccination?

Immunity in question

Studies that have attempted to determine the duration of immunity developed by sick people are quite contradictory, ranging from a few weeks to eight months. If we consider one of the most recent publications on the subject, from a cohort of 30,000 people screened in New York, the developed antibodies would be reactive for 5 months. Beyond that, the vaccine response would then again be needed.

Like the High Authority for Health which presented priority populations for vaccination against Covid-19 this week, a group of scientists commissioned by the National Academy of Siences in the United States issued these kinds of recommendations in October. Specifying, however, that “many unknowns remain regarding the safety and efficacy of vaccines in certain populations […] especially with regard to individuals previously infected with COVID-19. “

Patients excluded

The High Authority for Health, in the opinion published at the beginning of the week, specifies that “most of the clinical trials conducted on vaccine candidates exclude” previously infected subjects “in the main analysis, that is, already ill in the past.

Several laboratories such as Moderna or Novavax have in fact excluded from their tests people who test positive for Covid during diagnostic or antibody tests. Simply to limit errors. These positive cases may have already developed an antibody response to Covid-19, which could have skewed the results on the effectiveness of the vaccine itself. The conclusions of these tests therefore do not allow to establish whether the vaccine will be effective for all those who have already been infected. Especially if they suffer from persistent symptoms.

According to a study by the Hôtel-Dieu hospital, about a third of people who have fallen ill suffer from symptoms several weeks or even months after diagnosis. And many fear that a vaccine will intensify an already aggressive immune response that leads to fatigue, muscle aches, breathing difficulties or heart palpitations.

Vaccination possible, at term

Despite everything, the American Centers for Disease Control and Prevention states on their website that “since reinfection with Covid-19 is possible”, it may be advisable “for people to be vaccinated even if they have already been infected with Covid-19. “.

For its part, the Pfizer laboratory guarantees that the effectiveness rate of its vaccine, of 95%, is the same in participants who have already been infected with Covid-19. An item to be confirmed on larger patient samples.