COVID-19: Natural immunity only lasts a year

Infection and vaccination against SARS-CoV-2 helps build population immunity against the virus. This immunity in the general population is an important factor for vaccination strategies.

Although immunity against a pathogen is not made up of antibodies alone, the simplest strategy for assessing immunity is to carry out sero-epidemiological studies, i.e. to quantify, on a representative sample of the population, specific antibodies to the virus. Until now, most serological studies carried out after vaccination against COVID-19 have focused on specific population groups, including health professionals, who are not representative because they are on the front line facing the virus.

Other studies, conducted on other population groups, did not distinguish between participants who had or had not had a previous infection, or had not collected clinical and immunological data on the infection, explains the lead author. , Manolis Kogevinas, researcher at ISGlobal.

The study is conducted among 1,076 people aged 43 to 72 and thus concludes, not surprisingly, that the type of vaccine, age and mental health are factors strongly associated with antibody levels against COVID-19. Research confirms that hybrid immunity (vaccination plus infection) is more robust and long-lasting. The analysis of data from these participants in the COVICAT cohort, 6 months after the start of a wave of vaccination campaign, aimed to monitor the level and type of antibodies directed against 5 antigens of the virus: the protein Spike (S) full length, RBD receptor binding domain, S2 fragment, full length nucleoaspid (N) protein or N-terminal fragment. Using health records, the researchers were able to identify the factors determining the magnitude and duration of the antibody response in unvaccinated, vaccinated, or vaccinated and infected individuals. The analysis reveals that:

  • in 36% of people infected but not vaccinated,

antibodies are no longer detectable 1 year after infection,

especially in people over 60 and smokers.

  • On the other hand, vaccination made it possible to induce significantly higher levels of antibodies in people who had already had an infection vs those who had not had a previous infection; these antibody levels appear to be strongly associated with the magnitude of the response during infection.

Taken together, these results underscore the importance of vaccination, even in the case of prior infection.

  • Hybrid immunity is superior and longer lasting:

this clearly means, for vaccination campaigns, that people vaccinated but who have not been infected would need an earlier vaccination booster.

  • The factor most strongly associated with antibody level is the type of vaccine used: Moderna’s vaccine thus generates the highest antibody levels, although other factors also seem to play a role, including age well sure, but also mental illness.

“The association between mental health and antibody responses requires further research, but people with conditions such as depression, chronic stress or schizophrenia are known to have, in general, a lower response to vaccination “.

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