A series of studies found the Moderna vaccine to be more protective over time than the Pfizer-BioNTech vaccine. The reason is as follows.
After the Coronavirus vaccines were approved, federal health officials repeated the same refrain: They are all equally effective.
As it turns out, that wasn’t true.
A total of 221 million doses of the Pfizer-BioNTech vaccine have been dispensed in the United States, compared with 150 million doses of Moderna’s vaccine. A half-dozen studies published over the past few weeks suggest that Moderna’s vaccine is more protective than Pfizer-BioNTech’s.
Researchers evaluated the effectiveness of vaccines in preventing symptomatic illness among about 5,000 health care workers in 25 states in a study published on Wednesday in The New England Journal of Medicine. Compared to Moderna’s 96.3 percent effectiveness, Pfizer-BioNTech’s vaccine had 88.8 percent effectiveness.
Pfizer-BioNTech vaccine efficacy against hospitalization declined from 91 percent to 77 percent after four months following the second shot, according to CDC research published Friday. Over the same period, there was no decline in the Moderna vaccine.
Booster shots may be re-evaluated if the efficacy gap continues to widen. Some high-risk groups, such as older adults, will receive a third shot of the Pfizer-BioNTech vaccine this week.
There is a small but real difference between the Moderna and Pfizer-BioNTech vaccines, despite initial skepticism from scientists.
We assume that mRNA vaccines work similarly, but then we see a separation,” said Natalie Dean, a biostatistician at Emory University in Atlanta. There’s not a huge difference, but at least it’s consistent.”
She and others cautioned, however, that despite this discrepancy, both vaccines are still highly effective in preventing severe illness and hospitalization.
According to John Moore, a virologist at Weill Cornell Medicine in New York, there is likely a real difference between the two vials. “How important is this difference in the real world? ”
It’s not appropriate for people who took Pfizer to complain about inferior vaccines.
In the original clinical trials of the three vaccines ultimately approved in the United States, manufactured by Pfizer-BioNTech, Moderna, and Johnson & Johnson, it was evident that the Johnson & Johnson vaccine performed less well than the other two. That trend has continued since then, although J.&J. has announced that its vaccine’s efficacy is comparable to that of the other vaccines after a second dose.
In initial clinical trials, both Pfizer-BioNTech and Moderna vaccines had remarkably similar efficacy against symptomatic infection: 95 percent for Pfizer-BioNTech and 94 percent for Moderna. It was for this reason that they were described as more or less equivalent.
Over time, subtleties emerged. Vaccines have never been directly compared in a well-designed study, so data indicating that effects vary are largely based on observation.
The results of those studies could be skewed by a number of factors, including the location, the age of the vaccinated population, when they were immunized, and the timing between the doses, Doctor said.
Moderna’s vaccine was rolled out weeks before Pfizer-BioNTech’s to priority groups – older adults and healthcare workers. Older adults’ immune system declines more rapidly, so a decline observed in a group dominated by older adults may give the false impression that the Pfizer-BioNTech vaccine is no longer effective.
According to Doctor, a senior vice president at Pfizer, “I’m not convinced there is a difference.” “I don’t think there’s enough data to support that claim.”
The observational studies have produced results from a number of locations – Qatar, the Mayo Clinic in Minnesota, several other states in the United States – and among health care workers, hospitalized veterans or the general public.
The effectiveness of Moderna against severe illness in those studies ranged from 92 to 100 percent. By 10 to 15 percentage points, Pfizer-BioNTech’s numbers trailed.
Efficacy of the two vaccines against infection has diverged more sharply. Both vaccines waned over time, especially after the arrival of the Delta variant, but the Pfizer-BioNTech vaccine’s values decreased. More than 30 percentage points were gained by the Moderna vaccine in two recent studies.
According to a few studies, the Pfizer-BioNTech vaccine produced one-third to one-half the antibodies produced by the Moderna vaccine. Nevertheless, the decrease is trivial, according to Moore: Healthy individuals have antibody levels that are more than 100-fold higher.
Some experts, however, believe that a disparity would be worth exploring, at least among people who respond weakly to vaccines, including older adults and those with compromised immune systems.
At the end of the day, I do believe there are subtle, but real differences between Moderna and Pfizer,” says Doctor, an immunologist and physician at the University of Virginia in Charlottesville who co-authored the study published this month in JAMA Network Open. It might be relevant in high-risk populations. People should take a closer look.”
“Pfizer is a big hammer,” Doctor explained, but “Moderna is a sledgehammer.”
Divergence might be caused by a number of factors. There is a difference in the doses of the vaccines as well as the interval between the first and second doses.
It is typical for vaccine manufacturers to test a range of doses before choosing one – and they have done so for their trials of the Coronavirus vaccine.
However, in the midst of a pandemic last year, companies had to guess what the optimal dose was. Moderna went with 100 micrograms, Pfizer 30 micrograms.
A lipid nanoparticle is used in Moderna’s vaccine to deliver the larger dose. This vaccine’s first and second shots are staggered by four weeks, whereas the Pfizer-BioNTech vaccine’s are staggered by three weeks.
According to Moderna’s chief medical officer, Doctor, the extra week may give immune cells more time to proliferate before the second dose. “We need to study this further and do more research, but I think it’s plausible.”
A half-dose of the vaccine sent antibody levels soaring, according to Moderna’s team. A booster shot of 50 micrograms, the half dose, was requested by the company this month based on those data.
Neither the effect of that dose nor the duration of higher antibody levels is known. In order to authorize a booster shot of the half dose, federal regulators are reviewing Moderna’s data.
According to Doctor, both vaccines are still effective against severe illness and hospitalization, especially in people under 65.
Initially, scientists expected the vaccines to be 50 or 60 percent effective. “That would have been a great result for us all,” he said. Today, we’re debating whether 96.3 percent vaccine efficacy for Moderna is important versus 88.8 percent for Pfizer.