Feb 7, 2022 - Health

The kids' vaccine dilemma

Illustration: Gabriella Turrisi/Axios

Federal health regulators will soon face their next controversial vaccine decision: whether to authorize Pfizer's vaccine for children younger than 5, despite ongoing questions around dosing and effectiveness.

Why it matters: Once again, the pandemic is forcing health officials to choose between unconventional vaccine approval methods and the human costs of abiding by more traditional — yet time-consuming — regulatory processes.

State of play: At the request of the agency, Pfizer has asked the FDA for two doses of its coronavirus vaccine to be authorized for emergency use in children between 6 months and 5 years old, even though the plan is for the vaccine to eventually be given as a three-dose series.

  • The company announced in December that two doses of the vaccine didn't produce an immune response that cleared the required threshold in children 2-4 years old, and that it is testing a third dose.
  • Those results aren't expected until March, but giving two shots the go-ahead would allow parents to begin vaccinating their children — a months-long process — while data on the third dose is gathered.
  • Two doses did clear the antibody threshold in children 6 months to 2 years old. No safety concerns were found in either age group.

Yes, but: The results announced by Pfizer analyzed whether two doses of the vaccine — which were smaller than the ones given to adults — created an antibody response in small children that is roughly equivalent to that of people ages 16 to 25.

  • Two shots didn't produce an antibody response specifically matching that of 16-to-25-year-olds in 2-4 year olds, but it did in children younger than two. However, it appears two doses did offer protection against hospitalizations and death, as well as some protection against infection.
  • And clinical data on effectiveness has accumulated faster than anticipated, as the rapid spread of the Omicron variant has resulted in more cases among clinical trial participants.

Between the lines: Some experts worry that these nuances haven't been communicated well.

  • The initial argument against authorizing two doses was that, although they were somewhat effective, three doses would be necessary. But "people latched on to the idea that an ineffective two-dose vaccine might be authorized," University of Pittsburgh professor Walid Gellad said.
  • "The way the information on potential pediatric vaccine authorization has been rolled out is a problem — it has led to confusion, uncertainty, concern about integrity of the process" he added.

By the numbers: Pfizer's data shows that the vaccines were 57% effective against symptomatic disease in children ages 2–4, and were 50% effective in those aged 6 months to 2 years old, according to a person familiar with the data.

  • But these are results against both Delta and Omicron. It's likely that effectiveness against Omicron alone is lower, and that effectiveness against hospitalization is higher. The data is based a small sample size, the person cautioned.
  • Additionally, the antibody levels produced by two doses just missed the threshold for children ages 2 to 4, the person added, and are likely comparable to those elicited by two doses in older age groups.
  • Because neutralizing antibodies help protect against hospitalization and death, we know that "the two-dose regimen, on its own, will help protect kids against hospitalization and serious disease," the person familiar said.

The big picture: This won't be the first time that federal health regulators have to consider using an unconventional process to get ahead of the virus.

  • This tension was at the heart of last fall's booster debate as well, when some scientists felt that there wasn't yet enough data to justify the widespread recommendation of a third shot of the vaccine.
  • Ultimately, the FDA and the CDC slowed down the booster authorization timeline that had been envisioned by the Biden administration, and the entire process was criticized as messy and confusing.

What we're watching: An FDA advisory board will meet Feb. 15 to consider whether to recommend authorizing two doses of the vaccine. The FDA will then have to decide whether to authorize it, and the CDC will weigh in as well.

  • If the board sees data showing that two doses are safe and effective, the challenge will be deciding whether to authorize two doses without having information on what happens with a third dose, board member Paul Offit told Axios.
  • "They want us to have the option of giving parents the choice to do this, pending the third dose," Offit said. "It's unheard of, but then again, the pandemic is novel."

Editor's note: This story has been updated to clarify that two shots didn't produce an antibody response matching that of 16-25-year olds when tested in 2-4 year olds. It did, however, have a matching response in kids younger than 2.

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