A new study has raised concerns about how well the Moderna and Pfizer COVID-19 vaccines really work against the delta variant, worrying high-level officials.

Does Pfizer stop the delta variant? What about Moderna?

The study — which has been published on medrxiv and has not been peer-reviewed — found that Pfizer’s vaccine was 42% effective against infection in July, which was when the delta variant became dominant in the United States. Moderna’s vaccine was 76% effective in July.

  • Those numbers came specifically from data in Minnesota. However, the study said there was similar data found among those in Florida.
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Pfizer vs. Moderna in 2021 against delta variant

The study, which reviewed data from January to July, found that the Moderna vaccine, overall, was 86% effective against infection in that time period. Pfizer’s vaccine, meanwhile, was 76% effective against stopping infection.

  • For hospitalizations, Moderna’s vaccine was 92% effective and Pfizer’s was 85% effective.

What the new Moderna, Pfizer data means

The new data has caught the attention of the Biden administration, according to Axios.

  • “If that’s not a wakeup call, I don’t know what is,” one senior Biden official told Axios.
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Cornell virologist John Moore told Axios that there should be caution before reaching conclusions about the data.

  • “This is the kind of surprising finding that needs confirmation before we should accept its validity,” Moore told Axios.

More research on infections

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This study primarily deals with infections with little data about hospitalizations and death. So far, data from the Centers for Disease Control and Prevention has found that 99.999% of people who were fully vaccinated against COVID-19 — specifically through two shots of Moderna or Pfizer — did not have a severe breakthrough case that led to hospitalization or death, CNN reports.

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