Moderna vs. Pfizer: Both knockouts, but one seems to have the upper hand

It was then a constant refrain from federal health authorities Coronavirus vaccine Approved: All these shots are just as effective.

It turned out not to be true.

To date, approximately 221 million doses of Pfizer-BioNTech vaccine have been administered in the United States, compared to approximately 150 million doses of Moderna vaccine. In a half-dozen study published in the last few weeks, the Moderna vaccine appeared to be more long-term protective than the Pfizer-BioNTech vaccine.

A study published by the Centers for Disease Control and Prevention on Friday revealed the effectiveness of the Pfizer-BioNTech vaccine for hospitalization. Reduced from 91 percent to 77 percent 4 months after the second shot. The Moderna vaccine did not show a decrease during the same period.

If the effectiveness gap continues to widen, it can influence the discussion about booster shots. This week, federal agencies are assessing the need for a third dose of the Pfizer-BioNTech vaccine for some high-risk groups, including the elderly.

Scientists initially skeptical of the reported differences between the Moderna and Pfizer-BioNTech vaccines have gradually become convinced that the inequality is small but real.

Natalie Dean, a biostatistician at Emory University in Atlanta, said: “It’s not a big difference, but at least it’s consistent.”

However, the difference is small and the actual results are uncertain, as both vaccines are still very effective in preventing serious illness and hospitalization, she and others warned.

John Moore, a virologist at Weill Cornell Medicine in New York, said: “But really, how important is this difference in the real world?”

“It is not appropriate for people who take Pfizer to be surprised to get the inferior vaccine.”

Even the first clinical trials of three final US-approved vaccines (Pfizer-created by BioNTech, Moderna, Johnson & Johnson) J. & J. The vaccine was less effective than the other two. Research since then confirms that trend, but J. & J. This week, we announced that a second dose of the vaccine would increase its effectiveness to levels comparable to other vaccines.

The Pfizer-BioNTech and Moderna vaccines rely on the same mRNA platform and in initial clinical trials had very similar efficacy against symptomatic infections. 95% of Pfizer-BioNTech When 94% of Moderna.. This was part of the reason they were described as more or less equivalent.

Subtleties have emerged over time. Since vaccines have never been directly compared in carefully designed studies, the data showing different effects are primarily observational.

The results of these studies can be distorted by a variety of factors, including location, age of the vaccinated population, time of immunization, and timing between doses, Dr. Dean said.

For example, the Pfizer-BioNTech vaccine was rolled out a few weeks ago to Moderna’s priority group of seniors and healthcare professionals. Since immunity weakens faster in the elderly, the decline observed in groups consisting primarily of the elderly can give the false impression that protection from the Pfizer-BioNTech vaccine declines rapidly.

“I’m not sure there’s a real difference,” said Dr. Bill Gruber, senior vice president of Pfizer, in light of these warnings. “I don’t think there is enough data there to make that claim.”

But now, observational studies come from many places — Qatar, NS Mayo Clinic, Minnesota, Several other states in the United States — and healthcare professionals, hospitalized veterans, or the general public.

The effectiveness of Moderna for severe illness in these studies ranged from 92 to 100 percent. Pfizer-BioNTech numbers are down 10 to 15 percentage points.

The two vaccines differ more rapidly in their effectiveness against infection. Protection from both was weakened over time, especially after the arrival of the Delta variant, but the value of the Pfizer-BioNTech vaccine was lower. In two recent studies, the Moderna vaccine was superior in disease prevention by more than 30 percentage points.

In some studies antibody The Pfizer-BioNTech vaccine produced one-third to one-half that produced by the Moderna vaccine. Still, the reduction is trivial, Dr. Moore said: for comparison, there are more than 100-fold differences in antibody levels between healthy individuals.

Still, other experts said the corpus of evidence points to disparities worth investigating, at least in people who are vulnerable to the vaccine, including the elderly and people with immunodeficiency.

“In the end, I think there are subtle but real differences between Moderna and Pfizer,” said Jeffrey, an immunologist and doctor at the University of Virginia, Charlottesville, who co-authored such a study. Dr. Wilson Published in JAMA Network Open this month. “In high-risk populations, it may be relevant. I hope people take a closer look.”

“Pfizer is a sledgehammer,” Dr. Wilson added, “Moderna is a sledgehammer.”

Several factors may underlie the divergence. Vaccines vary depending on the dose and the time between the first and second doses.

Vaccine manufacturers usually have enough time to test different doses before choosing one. And we are doing such a test for testing the coronavirus vaccine in children.

But in the midst of last year’s pandemic, companies had to guess the optimal dose. Pfizer weighed 30 micrograms and Moderna weighed 100 micrograms.

Moderna vaccines rely on liquid nanoparticles that can deliver higher doses. And the first and second shots of that vaccine are four weeks off compared to the three Pfizer-BioNTech vaccines.

Dr. Paul Burton, Chief Medical Officer of Modana, said the extra week may give more time for immune cells to proliferate before the second dose. “We need to keep studying this and do more, but I think it’s plausible.”

The Moderna team has recently received half the dose of the vaccine yet Soaring antibody levels transmitted.. Based on these data, the company requested the FDA this month to approve 50 micrograms (half the dose) as booster shots.

There is limited evidence of the effect of that dose and nothing about how long the higher antibody levels will last. Federal regulators are reviewing Moderna’s data to determine if the available data is sufficient to approve half-dose booster shots.

Finally, both vaccines are not yet Stable retention Against Severe illness When hospitalizationDr. Moore said, especially for people under the age of 65.

Scientists initially wanted the vaccine to be 50% or 60% effective. “We would all have seen it as a great result and were happy with it,” he said. “We’ve been fast-forwarding to discuss whether Moderna’s 96.3% vaccine efficacy and Pfizer’s 88.8% vaccine efficacy are significant.”