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After the coronavirus vaccines were approved, federal health officials were consistently shunned: All of these vaccines are equally effective.
It turns out that this is not true.
Approximately 221 million doses of Pfizer-BioNTech vaccine have been distributed in the United States to date, compared to approximately 150 million doses of Moderna vaccine. In half a dozen studies published in the past few weeks, Moderna’s vaccine has been shown to be more protective over the long term than the Pfizer-BioNTech vaccine.
Research published Friday by the Centers for Disease Control and Prevention found that the Pfizer-BioNTech vaccine has efficacy against hospitalization. fell from 91 percent to 77 percent after a period of four months after the second shot. The Moderna vaccine did not decline over the same period.
If the efficacy gap continues to widen, it could have implications for the debate over supporting shots. Federal agencies are this week assessing the need for a third Pfizer-BioNTech vaccine for certain high-risk groups, including older adults.
Initially skeptical of the reported differences between the Moderna and Pfizer-BioNTech vaccines, scientists gradually became convinced that the difference was small but real.
“Our basic assumption is that mRNA vaccines work similarly, but then you start to see a divergence,” said Natalie Dean, a biostatistician at Emory University in Atlanta. “It’s not a huge difference, but at least it’s consistent.”
But the discrepancy is small, and real-world results are uncertain, because both vaccines are still highly effective at preventing serious illness and hospitalizations, he and others cautioned.
“Yes, it’s a real difference that probably reflects what’s in the two bottles,” said John Moore, a virologist at Weill Cornell Medicine in New York. “But really, how important is this difference in the real world?”
“It’s not okay for people taking Pfizer to go crazy because they have a lower quality vaccine.”
Even in the original clinical trials of three vaccines that were eventually authorized in the United States—Pfizer-BioNTech, Moderna, and Johnson & Johnson—J.&J. the effectiveness of the vaccine was lower than the other two. Research since then has confirmed this trend, but J.&J. announced this week that the second dose of its vaccine has increased its effectiveness to comparable levels.
The Pfizer-BioNTech and Moderna vaccines are based on the same mRNA platform and had very similar efficacy against symptomatic infection in initial clinical trials: 95 percent for Pfizer-BioNTech and 94 percent for Moderna. This was partly why they were described as more or less equivalent.
The subtleties emerged over time. Vaccines have never been directly compared in a carefully designed study, so data showing varying effects are mostly based on observation.
Dr. Results from these studies can be skewed by any number of factors, including location, age of the vaccinated population, when they were vaccinated, and timing between doses, Dean said.
For example, the Pfizer-BioNTech vaccine was administered to priority groups – older adults and healthcare workers – weeks before Moderna. Immunity declines more rapidly in older adults, so the decline observed in a group of mostly older adults may give the false impression that protection from the Pfizer-BioNTech vaccine is declining rapidly.
Given these caveats, Pfizer’s senior vice president, Dr. “I’m not really convinced there’s a difference,” said Bill Gruber. “I don’t think there is enough data to make this claim.”
But so far, observational studies have yielded results from a number of places – Train, NS Mayo Clinic in Minnesota, in several other states in the United States — and among healthcare workers, hospitalized veterans, or the general population.
Moderna’s efficacy against serious diseases in these studies ranged from 92 percent to 100 percent. It followed Pfizer-BioNTech’s figures by 10 to 15 percentage points.
The two vaccines diverged more sharply in their effectiveness against infection. Protection from both decreased over time, especially after the arrival of the Delta variant, but the values of the Pfizer-BioNTech vaccine dropped further. In two of the recent studies, the Moderna vaccine was more successful in preventing diseases by more than 30 percent.
A few studies have antibodies Those produced by the Pfizer-BioNTech vaccine were one-third to half of those produced by the Moderna vaccine. Still, this decline is insignificant, said Dr. Moore: For comparison, there is more than a 100-fold difference in antibody levels between healthy individuals.
Understand the Vaccine and Mask Instructions in the US
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- vaccination rules. On August 23, the Food and Drug Administration Pfizer-BioNTech’s coronavirus vaccine granted full approval It paves the way for people aged 16 and over to increase their tenure in both the public and private sectors. became private companies increasingly mandatory vaccines for employees. Such powers legally allowed and upheld in court appeals.
- Mask rules. Centers for Disease Control and Prevention in July suggested The fact that all Americans, regardless of vaccination status, wear masks in public in areas with outbreaks was a reversal of the guidance it presented in May. See where the CDC guidance applies, and where states created their own mask policies. The battle over masks has become contentious in some states. local leaders defying state bans.
- Colleges and universities. More than 400 colleges and universities require their students to be vaccinated against Covid-19. Nearly all in states that voted for President Biden.
- Schools. Both of them California and New York City imposes vaccination requirements for education personnel. A survey published in August found that many American parents with school-age children are against compulsory vaccinations for students, but More support for mask missions for unvaccinated students, teachers and staff.
- Hospitals and medical centers. Many hospitals and major healthcare systems require their employees to be vaccinated against Covid-19. By citing increased caseloads fueled by the delta variant and stubbornly low vaccination rates in their communities, even within the workforce.
- New York City. Proof of vaccination is required for workers and customers. indoor dining, gyms, performances and other indoor situations, but the app doesn’t start until September 13. Teachers and other education workers The city’s large school system will need at least one dose of the vaccine by September 27, with no weekly testing option. City hospital staff they should also be vaccinated or undergo weekly tests. Similar rules apply to New York State employees.
- at the federal level. The Pentagon has announced that it will try to make coronavirus vaccines mandatory for the country. 1.3 million active-duty soldiers No later than mid-September. President Biden announced all civilian federal employees would have to get vaccinated against coronavirus or subject to regular testing, social distancing, mask requirements and restrictions on most trips.
Still, other experts said the evidence points to a disparity worth investigating, at least in people who respond poorly to vaccines, including older adults and immunocompromised people.
D., an immunologist and physician at the University of Virginia at Charlottesville and co-author of one such study. “At the end of the day, I think there are subtle but real differences between Moderna and Pfizer,” said Jeffrey Wilson. Published in JAMA magazine this month. “In high-risk populations, it may be relevant. People better take a closer look.”
“Pfizer is a big hammer,” added Dr. Wilson, however, “A modern sledgehammer.”
Several factors may underlie the difference. Vaccines differ in their doses and the time between the first and second doses.
Vaccine manufacturers will typically have ample time to test a series of doses before selecting a dose, and they have done these tests for coronavirus vaccine trials in children.
But in the midst of a pandemic last year, companies had to estimate the optimal dose. Pfizer went with 30 micrograms, Moderna with 100 micrograms.
Moderna’s vaccine is based on a liquid nanoparticle that can deliver a larger dose. And the first and second shots of this vaccine stagger at four weeks, compared to three weeks for the Pfizer-BioNTech vaccine.
Moderna’s chief medical officer, Dr. An extra week can give immune cells more time to multiply before the second dose, Paul Burton said. “We need to continue to study this and do more research, but I think it’s reasonable.”
Moderna’s team recently reported that half a dose of the vaccine is still levels of sent antibodies rise. Based on that data, the company asked the FDA this month to authorize a half dose of 50 micrograms as a booster shot.
There is limited evidence to show the effect of this dose and none about how long high antibody levels can last. Federal regulators are reviewing Moderna’s data to determine if the current data is sufficient to allow a half-dose booster shot.
After all, both vaccines are still keep constant against serious illness and hospitalization, especially in people under the age of 65, Dr. said Moore.
Scientists initially hoped that vaccines would have an efficacy of 50 or 60 percent. “We would all see it as a great result and be happy about it,” he said. “Fast forward so far, and we’re debating whether 96.3 percent vaccine effectiveness for Moderna and 88.8 percent for Pfizer matters.”
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