People who received the Moderna COVID-19 vaccine had “slightly higher” antibody levels than those who received the Pfizer, now formally called Comirnaty, shot, according to a new small study.
While both vaccines insert molecules called mRNA that teach our bodies how to produce coronavirus antibodies, the Moderna shot uses more than three times the amount of mRNA than the Pfizer vaccine. This, the University of Virginia School of Medicine researchers say, could explain their findings.
So, does that mean the Moderna vaccine offers better protection against COVID-19?
Not necessarily, the team says. It’s still unclear if more antibodies equals more or better protection against the disease. There’s also more to an immune system than antibodies, including T cells and B cells, which the researchers did not study.
The findings are “just a small piece in a much larger puzzle” in scientists’ hunt to learn if one vaccine may be “superior” for certain demographics.
But what matters most is that both the Moderna and Pfizer COVID-19 vaccines have protected most people from severe disease and death, researchers say. Although breakthrough infections after vaccination are possible, they are not as common as infections among the unvaccinated. Researchers did not include the Johnson & Johnson coronavirus vaccine in its comparisons.
The study was published Sept. 2 in the journal JAMA.
“The thing that will be interesting is figuring out if measuring antibody levels ends up being a good marker of vaccine protection,” study co-author Dr. Jeffrey Wilson, an immunologist at the University of Virginia, said in a statement. “At the moment, we don’t know for sure.”
The team examined blood samples from 167 vaccinated university employees collected anywhere between one week to a month after their second doses; 79 received the Pfizer vaccine and 88 got the Moderna shot. Recipients were 42 years old, on average, and most (72%) were women.
Those who got the Moderna vaccine had more antibodies (about 69 micrograms per milliliter) in their blood than people who got the Pfizer shot (about 46 micrograms per milliliter) — regardless of age.
However, those who were aged 50 and older and received the Pfizer vaccine produced fewer antibodies compared to younger recipients after their second dose.
The study’s findings align with those of a separate study published Aug. 30., which found among 1,647 hospital workers in Belgium, those who were vaccinated with the Moderna vaccine developed nearly three times more antibodies than those who got the Pfizer shot.
The results held true even among people who previously had COVID-19 and those who did not. The Belgium study also speculates Moderna’s heavier usage of mRNA in its vaccine could explain the difference in antibody levels; it also suggests the time frame between doses (four weeks for Moderna versus three weeks for Pfizer) may play a role.
However, experts agree more research is needed before they can conclude one vaccine is more protective for some or all groups over the other.More than 175.9 million Americans are fully vaccinated as of Sept. 4, about 53% of the total population, according to a Centers for Disease Control and Prevention tracker. Of those, more than 95.5 million have received the Pfizer vaccine and 66 million have received the Moderna shot.