Health officials are stressing the importance of coronavirus vaccine booster shots as the Omicron variant spreads around the world, but millions of Americans aren't yet eligible for another dose.
Why it matters: Two doses of Pfizer and Moderna's vaccines — or one dose of J&J — aren't very protective against Omicron infection, according to preliminary data, although they likely work much better against severe disease.
- But some experts warn that giving a booster shot too soon could diminish its effects.
Where it stands: Anyone 16 and older who got their second Pfizer or Moderna shot at least six months ago is eligible for a booster shot in the U.S., as are people who received a J&J shot at least two months ago.
- But 58 million Americans received their second shots within the last six months, per CDC data.
- Children aged 5–11 just became eligible for vaccines last month, meaning none of them are yet eligible for a third shot.
Driving the news: Adults in the U.K. are now eligible for booster shots three months after their second dose, and Denmark announced this week that it's making booster doses available to adults older than 40 after 4.5 months.
Yes, but: Experts warn that changing the timing of a third dose isn't a decision to be made lightly.
- "The main point of the six months interval is to allow affinity maturation and quality improvements in the immune response. That takes a finite amount of time," said Cornell virologist John Moore.
- "It's difficult to say if boosting nine weeks [after the primary series] would meaningfully impact durability," said Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization. "Longer intervals appear to induce better antibody responses even for two-dose regimes, so three doses in a short interval might not provide substantial benefit."
The big picture: Early data show that two doses of Pfizer's vaccine are only marginally effective at preventing Omicron infection, and that booster shots are much more effective.
- However, a South African analysis found that two Pfizer shots are 70% effective against hospitalization.
- That means that there's almost certainly a window of time when fully vaccinated people are vulnerable to Omicron infections — albeit pretty well protected against severe disease — but not yet eligible for a booster shot.
- It's at least worth looking at changing the interval, "given that we have evidence that protection decreases before we are planning to give the booster," said Gigi Gronvall, a senior scholar at the Johns Hopkins Center for Health Security.
The bottom line: Booster decisions are being made without good data about when is the ideal time to get them. Some experts argue they're also being made without a clear goal as to their purpose.
- "The question is, what is the goal of this vaccine?" said Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia.
- People vaccinated less than six months ago "should be reassured that they are in all likelihood protected against serious illness," he added.