The American laboratory Moderna's vaccine against Covid-19 is capable of producing antibodies that persist 90 days after injection, according to the study of 34 participants at the start of clinical trials published on Thursday in the medical journal New England Journal of Medicine.
These are the first data over a period of several months to have been independently validated by a scientific journal.
Participants will be followed for 13 months to check for longer-term protection, the study authors say.
The term of protection is undoubtedly longer
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Researchers from the National Institutes of Health tested the level of two types of antibodies to the coronavirus 90 days after the second dose of the vaccine, which itself is given 28 days after the first.
They observed a "slight" and expected drop in the level of antibodies in the vaccinated participants, but at a level which remained high and above the natural immunity observed in former patients recovered from Covid-19.
In addition, no serious side effects were observed in the so-called phase 1 trial, which began in March.
As recalled by Jean Castex, presenting his strategy for vaccinating the population on Thursday, the vaccine from the American Moderna is one of those that will be deployed in France, with that of Pfizer-BioNtech and that of the British AstraZeneca.
An immune memory created for "a while"
Antibodies are only one component of the immune response, along with B (immune memory, antibody production) and T lymphocytes (which kill infected cells).
The researchers note that the data on immune memory cells is not yet known, but previous studies have shown that the vaccine elicits killer cells well.
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US specialist Anthony Fauci, director of the Institute of Infectious Diseases, recently said he was "certain" that the immune memory created by the vaccine would last for some time.
"We do not know if it will be one, two, three or five years, we do not know," he said, however.
Only time will tell.
"It's pretty positive news overall," said Benjamin Neuman, a professor at Texas A&M University, on Thursday of the study, noting that even in the elderly the immune response remained "reasonably strong."