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Illustration: Annelise Capossela/Axios

As the Delta variant continues to drive a fourth wave of the coronavirus pandemic in the U.S., Biden officials see a booster shot among at least some vaccinated Americans as increasingly likely.

Why it matters: Another round of shots — beginning as early as late fall — could not only boost the level of protection against the virus among the vaccinated, but also help curb its spread throughout the population.

Between the lines: The amount of neutralizing antibodies a person has following their first two doses of Pfizer and Moderna's coronavirus vaccines appears to drop over time, which is a very normal thing to happen with vaccines.

  • The outstanding scientific question has been what that means for the person's overall protection against the virus, especially because neutralizing antibodies aren't the body's only form of immunity.
  • Some Biden officials are increasingly convinced that high levels of neutralizing antibodies correlate with a higher degree of protection against illness. They worry that means that as more time passes, vaccinated people may be increasingly vulnerable to mild, moderate or even severe disease, a Biden official told Axios.

The New York Times first reported on Friday that Biden administration health officials increasingly think that vulnerable populations will need booster shots.

  • This growing consensus is "tied in part to research suggesting that the Pfizer vaccine is less effective against the coronavirus after about six months," per the NYT.
  • Vaccine manufacturers have been warning for months that some Americans could require booster shots as soon as September.

The big picture: There's currently no data suggesting that people who have received a shot — even those who were among the first to get vaccinated — are at risk of becoming severely sick if they get a breakthrough infection.

  • That doesn't mean they never will be. And recent data suggest that protection against asymptomatic or mildly symptomatic disease does decrease over time.
  • Although vaccine efficacy against severe disease seems to be holding steady among the three vaccines authorized for use in the U.S., some officials worry that may not continue to be true, the Biden official said, adding that boosters could begin as early as late fall.

Officials also believe that a booster shot may reduce the chances that a vaccinated person can transmit the virus, which would help reduce its overall prevalence in the U.S. — particularly if the Delta variant causes cases to rise as much as it's predicted to.

What we're watching: The Biden administration has purchased enough doses of vaccine to ensure that the U.S. will have enough for anyone who wants a booster to receive one.

  • The rest of the world, however, is likely to question why Americans should receive a third shot while billions of people around the globe wait for their first.

Go deeper

Updated 4 hours ago - Politics & Policy

Omicron dashboard

Illustration: Brendan Lynch/Axios

  1. Health: Pfizer and Moderna boosters overwhelmingly prevent Omicron hospitalizations, CDC finds — Omicron pushes COVID deaths toward 2,000 per day — The pandemic-proof health care giant.
  2. Vaccines: The case for Operation Warp Speed 2.0 — Starbucks drops worker vaccine or test requirement after SCOTUS ruling — Kids' COVID vaccination rates are particularly low in rural America.
  3. Politics: Biden concedes U.S. should have done more testing — Arizona says it "will not be intimidated" by Biden on anti-mask school policies — Federal judge blocks Biden's vaccine mandate for federal workers.
  4. World: American Airlines flight to London forced to turn around over mask dispute — WHO: COVID health emergency could end this year — Greece imposes vaccine mandate for people 60 and older — Austria approves COVID vaccine mandate for adults.
  5. Variant tracker
Oct 30, 2021 - Health

Texas AG sues Biden administration over vaccine mandate for contractors

Texas Attorney General Ken Paxton speaks during the Conservative Political Action Conference in Dallas on July 11. Photo: Dylan Hollingsworth/Bloomberg via Getty Images

Texas Attorney General Ken Paxton is suing the Biden administration over its vaccine mandate for federal contractors, which requires vaccination against the coronavirus no later than Dec. 8.

What they're saying: The executive order is "a dramatic infringement upon individual liberties, principles of federalism and separation of powers, and the rule of law," according to the lawsuit, which was filed Friday evening in the U.S. District Court for the Southern District of Texas.

Oct 31, 2021 - Health

Moderna says FDA needs more time to assess risks of vaccine in teens

Photo: Miyer Juana/Long Visual Press/Universal Images Group via Getty Images

Moderna said Sunday that the Food and Drug Administration (FDA) is delaying a decision on approving the emergency use of the company's coronavirus vaccine for children ages 12 to 17.

Driving the news: The FDA informed Moderna that it is evaluating the risk of myocarditis, a condition affecting the wall of the heart, after vaccination, per the release.