If You Got This COVID Vaccine, You Could Be Protected Longer, Study Says
New research shows that this type of shot generated a very promising immune response.
The Biden administration announced in August that COVID-19 vaccine boosters would soon be made available to the general public. But since then, a fresh debate has begun over whether or not all fully vaccinated people need additional shots eight months after their last dose due to waning immunity. Mounting evidence has suggested that many of those who have received all necessary shots of the vaccine are highly protected against hospitalization or death from the disease, even in the face of the highly contagious Delta variant. But now, a new study has found that the Moderna vaccine generates a particularly strong immune response, potentially meaning that those who initially received it are protected longer than originally thought.
The latest findings, which were published in the journal Science on Sept. 14, come from a team of researchers from La Jolla Institute for Immunology (LJI) who set out to study how long immunity against COVID-19 would last in patients given the Modern mRNA vaccine at different dosage levels. The team compared the immune responses seen in recovered COVID patients with those who had received two 25 microgram (mg) injections of the vaccine 28 days apart—which is a quarter of the 100 mg doses currently administered in shots—during phase one clinical trials.
The team found that even the lower dose generated strong CD4+ (helper) T cell, CD8+ (killer) T cell, and antibody responses for at least six months after the second shot was administered. They concluded that the immune response would likely last much longer beyond the initial window, with data showing that all age groups saw a sustained immune memory—even those in the highly vulnerable 70-and-older demographic.
"This time point is critical because that is when true immune memory has formed," Daniela Weiskopf, PhD, a co-leader on the study and a research assistant professor from LJI, said in a statement.
"The immune memory was stable, and that was impressive," Shane Crotty, PhD, a co-leader on the study from LJI, added. "That's a good indicator of the durability of mRNA vaccines." Still, he noted that the results still cannot determine if a lower dose offers the same level of protection as those currently being administered, saying that "it would take a clinical trial" to determine the actual efficacy.
The newly published results appear to add to a mounting body of evidence from other researchers that Moderna shots generate a larger immune response. One such study published on Aug. 16 in JAMA Internal Medicine analyzed the vaccine response in more than 950 health care workers from the John Hopkins Health System. Results found that those who received Moderna developed more spike IgG antibodies than those who got Pfizer.
And even beyond the generated 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 shots.
"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.
The LJI team announced they plan to continue research that will help determine how protective other types of vaccines are against COVID-19. But for now, Weiskopf notes that real-world data shows currently available shots appear to maintain their effectiveness over time. "The people in the hospitals are the ones not vaccinated," she said.