Aug 20, 2021 - Health

The importance of vaccine timing

Illustration of a syringe in a bottle of insulin with a clock face cap
Illustration: Sarah Grillo/Axios

More time between COVID vaccine doses may help build more durable immunity, experts say.

Why it matters: The three- or four-week interval between the first and second doses of the Pfizer and Moderna vaccines was relatively short — and may help explain why the U.S. is now preparing for third doses.

What they're saying: "When you make that decision to do a three- or four-week interval, it sacrifices length of protection and durability of protection," said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College.

  • He said it was a smart decision to pursue that vaccine interval early on, "because so many Americans were losing their lives from COVID — 3,000 deaths per day — and we had to get people fully immunized."
  • But it also made boosters much more likely, he said.
  • Longer intervals between doses may allow the immune system time to mature, or allow antibodies to improve in quality while dwindling in number, John Moore, a professor of microbiology and immunology at Cornell, told MedPage Today.

Between the lines: On Thursday, a report from U.K. health officials offered similar observations.

  • COVID vaccines were more effective against symptomatic disease with at least six weeks between doses than with only three to four weeks between doses, the paper says.

What we're watching: Experts say the eight-month gap the U.S. is planning before third doses could offer a significant boost.

  • "That may be it for a while, we may not need annual boosters," Hotez told MedPage. "This could be the third and done."
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