March 1, 2022 -- You may have already seen the headline: The Pfizer vaccine’s effectiveness against COVID-19 infection drops to 12% in 5- to 11-year-olds. But how do experts interpret this and other results from this preprint study?
Despite the findings, which have not been peer-reviewed, researchers at the New York State Department of Health, who did the study, say vaccination of children 5 years and older remains essential to prevent severe COVID-19 disease.
The study data shows that "COVID-19 vaccines reduce the risk of more severe illness and hospitalization for children 5-11," New York State Department of Health Commissioner Mary Bassett, MD, said in a statement.
"I encourage parents and guardians to consult their pediatrician about getting their children vaccinated, and boosted if eligible, as soon as they can," said Bassett, a study co-author.
Adam Ratner, MD, a member of the American Academy of Pediatrics Committee on Infectious Diseases, says doctors need to talk with patients and parents to make sure this study doesn’t discourage them from getting children vaccinated.
Part of that talk would be telling them vaccination "is still the best option that we have right now for protection of kids in that age range,” he says.
Although hospitalizations of children during the Omicron surge was rare, compared to the rate in adults, he says, most admissions were among unvaccinated children.
One-Third the Dose
It could be the dose, not the vaccine, per se, behind the drop from 65% to 12% effectiveness of the vaccine during the Omicron surge. Children in this age group typically receive one-third the dose, or 10 micrograms, per shot, compared to a 30-microgram dose for adults and children 12 years and older.
"The data are not surprising as the vaccine was developed in response to an earlier COVID-19 variant, and reduced effectiveness of two doses against the Omicron variant has been seen to some degree with all vaccines and ages," Bassett said.
The results were published Monday as a preprint study on MedRxiv. Preprints carry a caveat that the information "has not been certified by peer review. It reports new medical research that has yet to be evaluated and so should not be used to guide clinical practice."
Putting the Onus on Omicron
Previous studies of children 5 to 17 support the safety and effectiveness of the Pfizer COVID-19 vaccine, the researchers point out. But the research was done before the Omicron variant was so widespread.
One study from Pfizer during the Delta surge, for example, reported 90% vaccine efficacy among 5- to 11-year-olds.
Bassett and colleagues looked at infection and hospitalization numbers in New York state starting in late November. They compared COVID-19 cases of both fully vaccinated and unvaccinated children ages 5 to 11 and 12 to 17 using a state database.
In the 12- to 17-year-olds, vaccine efficacy dropped from 85% on Nov. 29 to 51% on Jan. 24, when Omicron accounted for 99% of circulating virus strains.
In the 5- to 11-year-olds, vaccine efficacy decreased from 68% the week of Dec. 13 to 12% by Jan. 24.
Vaccine efficacy was stronger against hospitalization than for preventing infection. The rate of hospital admission was 73% in the older age group and 48% in the younger children.
'Best Tool We Have'
"The vaccine is the best tool we have, and it's way, way better than not vaccinating," Ratner said. "And it's certainly safe. There is nothing that would indicate any kind of safety issue for 5- to 11-year-olds."
In addition, vaccinating children 5 years and older makes even more sense he said, now that mask mandates and other protections are easing.