But these are exceptions; many countries still recommend two doses of the Covid-19 vaccine for everyone and issue vaccination warrants that make no exceptions for people who have already had Covid-19.
The rationale for these general recommendations is that not everyone develops a strong immune response after infection. And the data shows that while so-called natural immunity can last for a long time – perhaps up to a year – the length varies depending on factors such as a person’s age, medical conditions, and the severity of the disease. .
But studies also suggest that otherwise healthy people who previously had Covid-19 show equal or greater levels of immune responses after one dose of the vaccine compared to people with two doses and no previous infections. People with hybrid immunity also don’t seem to gain much more immunity from a second dose, suggesting that second injections may not be necessary for them (although future boosters may still be needed). .
A more adapted approach may be interesting to consider for certain groups.
Children, for example, are much less likely than adults to become seriously ill from Covid-19. And there is a risk, although rare, of vaccine-related myocarditis (inflammation of the heart) which is more common in young people, especially boys, after their second dose of an mRNA vaccine. Some countries like Norway and Great Britain only give one dose of Pfizer vaccine to children aged 12 to 15 to avoid potential risks like myocarditis from the second dose.
But giving all children a single dose comes with concerns that a single dose will not provide strong, long-lasting protection. Whether or not a child has had Covid-19 is not part of those vaccination decisions – and should be.
If scientists and policymakers consider the power of hybrid immunity, it is reasonable to recommend a single dose for children without serious health problems who have had Covid-19. If parents are unsure whether their children have ever been infected, antibody tests may be done when they receive their first dose of the vaccine. While these tests may not detect all children who have had Covid-19, they would detect most, and only children without a confirmed infection could be called back for a second dose. Such an approach could also help free up doses for the many other countries with low vaccine supplies and for adults at risk who have not been vaccinated. The approach should at least be considered for further study.
There are other reasons for ignoring natural immunity in decisions about vaccination. Adding antibody tests to determine who had Covid-19 to an already logistically difficult vaccine deployment can be difficult. In countries like the United States with deep political divisions over vaccines, a ‘one size fits all’ strategy may be preferable to a more tailored approach which could create confusion, generate anti-vaccine sentiment and interfere with passport issuance. vaccine.