PARIS | immunity based on the antibodies acquired after curing of the COVID-19, would disappear most of the time in a few months, according to a new study, which may complicate the development of an effective vaccine in the long term.
“This work confirms that the responses in protective antibodies in people infected by the SARS-CoV-2 […] seem to decline rapidly”, underlines Monday, Dr. Stephen Griffin, professor in the School of medicine of the university of Leeds (Uk).
“The vaccines under development would either generate a stronger protection and more sustainable compared to natural infections or to be administered regularly,” says this physician, who was not involved in the study.
“If the infection gives you antibody levels that decrease in two to three months, the vaccine will be potentially the same thing”, and “a single injection may not be not sufficient,” says Dr. Katie Doores, main author of the study, in the Guardian.
The study of the prestigious King’s College of London, which has not yet been the subject of a peer review, has been put online on the site medRxiv.
The researchers studied the immune response of more than 90 confirmed cases (including 65 by tests, virological) and show that the levels of neutralizing antibodies, capable of destroying the virus, reach a peak average of about three weeks after the onset of symptoms, and then decline rapidly.
According to the blood tests, even individuals with mild symptoms have had an immune response to the virus, but generally less than in more severe forms.
Only 16.7% of subjects still had high levels of neutralizing antibody to 65 days after the onset of symptoms.
The study also tends to fly in the face of the policy based on herd immunity, which is supposed to protect everyone, once that a high percentage of the population has acquired immunity after being infected.
The specialists noted, however, that the immunity is not based on antibodies, the body producing immune cells (B and T) that play a role in the defense.
“Even if you find yourself without circulating antibodies detectable, this does not necessarily mean that you have no protective immunity because you probably have memory cells immune that can quickly come into action to start a new immune response if you encounter again the virus. It is therefore possible that you are getting an infection more benign,” says professor of immunology viral Mala Maini, consultant at University College London.
Pending more information, “even those who have an antibody test-positive – in particular those who can not explain where they may have been exposed – should continue to exercise caution, social distancing, and to use an appropriate mask,” warns James Gill, honorary professor of clinical at Warwick Medical School.