If You Got This Vaccine, You May Have Twice As Many Antibodies, Study Says
A new study shows that one vaccine could produce a much stronger immune response.
Over the past few months, COVID cases have surged once again across the U.S., thanks in large part to the fast-spreading Delta variant. The majority of new infections are among unvaccinated individuals, but headlines about breakthrough infections—which have hit everyone from major Hollywood celebrities to U.S. senators—have some vaccinated individuals wondering just how protected they are against the variant. The reality is that while the vaccines are still very effective, many things can affect your immune response from vaccination, including your age and preexisting medical conditions. And now, recent research suggests that the vaccine you got could also have an effect on the amount of antibodies you produce.
A study published Aug. 30 in the Journal of the American Medical Association compared antibody response following vaccination with both Pfizer and Moderna. The researchers analyzed nearly 2,500 health care workers from Belgium who had received two doses of either vaccine, measuring antibody levels prior to vaccination and six to 10 weeks after the second shot.
According to the study, participants who were vaccinated with Moderna had higher antibody levels than those who got Pfizer. This holds true for both those previously infected with COVID and those who were never infected, as well as across all age groups. Overall, the researchers found that Moderna's vaccine produces twice as many antibodies as the Pfizer vaccine—which could mean it's more protective, they say.
"A relationship between neutralization level after SARS-CoV-2 vaccination and protection against COVID-19 has been demonstrated by several studies," the researchers explained. "As such, the height of the humoral response after vaccination, which correlates with neutralizing antibody titers, might be clinically relevant."
The researchers for this study did not officially conclude why Moderna's vaccine produces a greater response, but they suggested that the differences might be explained by the higher amount of active ingredient in the Moderna vaccine or the longer interval in between doses. Each dose of Moderna contains 100 micrograms of vaccine, while each Pfizer dose contains just 30 micrograms. Pfizer is also administered with a three-week wait between shots, while Moderna has a four-week interval.
A separate study published on Aug. 16 in JAMA Internal Medicine found similar results. This study analyzed the vaccine response in more than 950 health care workers from the John Hopkins Health System and found that those who received Moderna developed more spike IgG antibodies than those who got Pfizer.
Outside of antibody response, recent research from the Mayo Clinic also showed how much more protective Moderna might be than Pfizer. According to this study, which was preprinted Aug. 8 on medRxiv, people who received Moderna's vaccine had a two-fold risk reduction for breakthrough infection compared to those who got Pfizer's.
"Our observational study highlights that while both mRNA COVID-19 vaccines strongly protect against infection and severe disease, further evaluation of mechanisms underlying differences in their effectiveness such as dosing regimens and vaccine composition are warranted," the Mayo Clinic researchers concluded.