Covid: one in three cured no longer have antibodies after a year

After contracting the SARS-CoV-2 once it doesn’t make you immune to new infections while get vaccinated after healing increases protection. This is not new, but a recent Spanish study has shown the greater effectiveness of the vaccination in those who have previously contracted the virus. The study also highlighted how about 36% of those who are cured can be without antibodies after a year.

The study, published in the journal BMC Medicine, was conducted by a group of researchers from the Barcelona Institute for Global Health and involved more than a thousand Spanish individuals between 43 and 72 years old. Participants underwent a serological test at the end of the first Spanish lockdown in 2020 and tested exactly one year later, 6 months after the arrival of the vaccines.

The collected data made it possible to determine the amount antibodies present in the organism of every individual, also in connection with theirs vaccination status and with the previous infection. Of the participants, only 64 were not vaccinated during the study and only 43 of them were still serologically positive.

For 8 of them it was not possible to determine the antibody levels, while for the remaining 13 they had completely disappeared. 20.3% of the participants not vaccinated was therefore devoid of antibodies to Sars-Cov-2, 36% if we also consider those for whom it was not possible to obtain the antibody titer. Absence of antibodies was much more common in participants who were asymptomatic at first infection.

Concerning the vaccinated, only 2% had no antibodies and only 1% had contracted the infection after vaccination. However, these data do not allow for conclusions to be drawn after one year, as vaccination had started about 6 months earlier from the second survey. However, among them, the antibody titer was higher in those who were vaccinated after contracting the infection.

Our data underscore the importance of vaccination, even for people who have been previously infected, and confirm that hybrid immunity is superior and longer lasting. This means that those who have been vaccinated but never infected will likely need a booster dose before those who have also contracted the virus.

Marianna Karachaliou, researcher who participated in the study

• Those who have recovered from Covid after a year have no antibodies in one in three cases (today.it)