Moderna’s vaccine against covid-19 lasts at least six months and there is no indicator that a booster dose is necessary, according to a study by the University of La Jolla (USA) published today in the journal Science.
The memory of the immune system remains strong during this period, even with a low dose of Moderna preparation, and is similar to the response of people who have recovered from the disease.
This period of time is “fundamental because it is when the true immunological memory is formed,” said Daniela Weiskopf, one of the authors of the research, cited by the university center.
Moderna’s preparation (mRNA-1273) elicited a strong response of CD4 + and CD8 + T lymphocytes, as well as antibodies, for “at least six months” after the participants in the clinical trial were fully vaccinated, although it is likely that the immune response could last longer.
This “strong” immune memory lasted in all age groups, even those over 70, a group especially vulnerable to severe covid-19.
Immune memory was stable, and that “was impressive,” it is “a good indicator” of the durability of messenger RNA vaccines, “added another of the study’s authors, Shane Crotty.
The researchers compared patients recovered from the disease with participants in the phase 1 trial of Moderna’s vaccine who received doses of 25 micrograms.
The objective was to see if with a quarter of the dose it was possible to induce an immune response, for which they had samples of the trial participants who had the two punctures with that smaller amount, received 28 days apart, explained José Mateus Triviño, lead author of the research.
Although the researchers don’t know if this smaller dose is as effective as the standard one (100 milligrams), the study shows that the T-cell and antibody response is still strong.
Moderna’s vaccine stimulates an adaptive immune response to the SARS-CoV-2 spike protein (the one it uses to enter cells) that is “almost identical” to that of the immune system in the face of a natural coronavirus infection.
“The answer is comparable,” said Weiskopf, “it is neither greater nor less” and the study does not show that a lower dose of the same protection as the standard one would require a clinical trial.
Research also shows the power of “cross-reactive” T cells, which play an important role in the control and resolution of covid infections.
The team already showed last year that T cells from people who had recovered from the common cold coronaviruses could respond to SARS-CoV-2, but it was not known whether this cross-reactivity could actually protect against Covid-19.
In the new study, they found that people with cross-reactive T cells had “significantly stronger” CD4 + T cell and antibody responses to both doses of the vaccine.
The researchers also focused on the CD8 + T cell response generated by Moderna’s vaccine, for which there was not yet enough data.
“We know that naturally recovered and infected people develop excellent CD8 + T cell responses against SARS-CoV”, highlighted Mateus Triviño.
The study shows a strong CD8 + T cell response to the low-dose Moderna vaccine, similar to that of a patient who fights infection naturally.