Why is this important: The efficacy gap could still disappear with more data, and both vaccines remain very effective against serious diseases. But if the gap persists, it raises questions about whether the two vaccines should be treated the same politically.
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Driving the news: Several studies – both preprints and those that have been peer reviewed – have found a difference between the effectiveness of the two vaccines over time, although some experts have warned that this could come from faulty direct comparisons.
- The studies evaluated different measures of effectiveness, but all found that the effectiveness against serious illnesses remained relatively high.
- “There have been kinds of signals coming from enough separate sources that are starting to paint a picture that may reflect a real biological phenomenon – a real difference. I’m starting to believe there’s something behind it, ”said Natalie Dean, a professor at Emery who specializes in designing vaccine studies.
Enlarge: In a study released last week, the CDC found that Moderna was significantly more effective against hospitalizations and emergency departments or appointments with emergency care than Pfizer or J&J vaccines.
Between the lines: Pfizer was the first vaccine authorized in the United States and began to be administered several weeks before the Moderna vaccine.
- “Because of the way the deployments went, the oldest, most vulnerable and sickest people, like nursing home residents, got Pfizer,” said Cornell virologist John Moore. .
- This means that part of the efficacy gap that appears in some studies may be the result of administering Pfizer earlier and in more vulnerable populations.
- However, the large CDC study that found a significant difference in vaccine effectiveness found that of Moderna to be higher at all ages.
Possible reasons for the difference include that Moderna has a much higher dosage regimen than Pfizer, and the second shot is given after a slightly longer interval.
Yes, but: The two vaccines are almost equal in their ability to “do what a vaccine should do, which is protect against serious disease,” said Paul Offit, director of the Vaccine Education Center at Children’s Hospital. of Philadelphia.
The bottom line: Moderna data may look more like Pfizer data after more time. But it may be unwise to use one as a proxy for the other.
- “It’s not clear that any lesson we’ll see from Pfizer will translate directly into Moderna,” Dean said. “I think if you asked this question a few months ago, then there was really [weren’t] all signals of a difference, people would group them together a lot in their minds. ”
What we are looking at: There is much more data – especially from other countries, like Israel – on the waning effectiveness of Pfizer and the effect of booster injections on restoring effectiveness to original levels.
- But if that data doesn’t apply to Moderna, regulators may not yet have a lot of data to work with when making recall decisions – an already highly controversial process.
- “We won’t know the real data specific to Moderna for some time now, on restoring efficiency and sustainability,” said Eric Topol, executive vice president of Scripps Research.
- Topol said there were signs that Moderna’s effectiveness was decreasing to some extent over time. “It can be longer and maybe less,” Topol added.
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