Moderna's vaccine against the coronavirus produces antibodies that persisted for 90 days after vaccination, according to the study of 34 participants at the start of the clinical trials, published Thursday in the New England Journal of Medicine.
The duration of protection is probably longer, but these are the first data over a period of several months, independently validated by a scientific journal.
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 28 days after the first.
They observed a "slight" and expected drop in antibody levels in vaccinated participants, but at a level that remained high, and also higher than the natural immunity found in previous recovering Covid-19 patients.
Additionally, no serious adverse events were observed in the Phase 1 trial, which started in March.
Antibodies are only one component of the immune response, along with B-cells (which produce antibodies) and T-cells (which kill infected cells).
The researchers note that data on the immune memory cells are not yet known, but previous studies have shown that the vaccine does induce the killer cells.
The Brussels Times