Study Says Pfizer COVID Vaccine Wanes in Kids Ages 5 to 11

March 1, 2022 — You may have seen the headline: Pfizer’s vaccine against COVID-19 infection drops to 12% in children ages 5 to 11. But how do experts interpret this and other results from this preliminary study? Despite the results, which have not been peer-reviewed, the New York State Department of Health researchers who conducted the study say that vaccinating children ages five and older is still essential to prevent severe illness from COVID-19.

The study data shows that “COVID-19 vaccines reduce the risk of more severe illness and hospitalizations for children ages 5-11,” said New York State Department of Health Commissioner Mary Bassett statement.

“I urge parents and caregivers to consult with their pediatrician about their children’s vaccinations and boosters, if they are eligible, as soon as possible,” said Bassett, co-author of the study.

Adam Ratner, MD, a member of the American Academy of Pediatrics Committee on Infectious Diseases, says doctors need to talk to patients and parents to make sure this study doesn’t stop them from getting their children vaccinated.

Part of that conversation will be telling them that vaccination “still is the best option we have right now to protect children in this age range,” he says.

While hospitalizations of children during the Omicron surge were rare, compared to adults, he says, the majority of hospitalizations were in unvaccinated children.

One-third of the dose

It may be the dose, not the vaccine per se, that is behind the drop in vaccine effectiveness from 65% to 12% during the Omicron spike. Children in this age group usually receive one-third of the dose, or 10 mcg, per shot, compared to the 30 mcg dose for adults and children 12 years of age and older.

“These data are not surprising since the vaccine was developed in response to an earlier variant of COVID-19, and a decrease in efficacy of two doses against the Omicron variant was observed to some extent across all vaccines and ages,” Bassett said.

The results were published on Monday as a preliminary study on MedRxiv. The preprints contain a disclaimer stating that the information “has not been verified by peer review. It reports on new medical research that has yet to be evaluated, and therefore No be used to guide clinical practice.”

Laying Responsibility on Omicron

The researchers note that previous studies in children ages 5 to 17 support the safety and efficacy of Pfizer’s COVID-19 vaccine. But the research was done before the Omicron variant became so widespread.

One study from Pfizer during the Delta surge, for example, reported 90% vaccine efficacy in children aged 5 to 11 years.

Bassett and his colleagues studied the number of infections and hospitalizations in New York state starting in late November. They compared cases of COVID-19 in both fully vaccinated and unvaccinated children aged 5 to 11 and 12 to 17 using a government database.

In children aged 12 to 17 years, the effectiveness of the vaccine dropped from 85% on November 29 to 51% on January 24, when Omicron accounted for 99% of the circulating strains of the virus.

In children aged 5 to 11 years, the effectiveness of the vaccine decreased from 68% in the week of December 13 to 12% by January 24.

The effectiveness of the vaccine was higher for hospitalization than for preventing infection. The hospitalization rate was 73% in the older age group and 48% in the younger age group.

“The best tool we have”

“A vaccine is the best tool we have, and it’s much better than no vaccination,” Ratner said. “And it is definitely safe. There is nothing to indicate any safety issue for children aged 5 to 11.”

In addition, vaccinating children aged 5 years and older makes even more sense, he said, now that requirements for masks and other protective equipment are easing.

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