Two doses of the Pfizer-BioNTech COVID-19 vaccine were protective against severe disease in children ages 5 to 11 during the last Omicron variant augmentation, but soon lost most of its ability to prevent infection in this age group, according to a study by New York State researchers. .
Vaccine efficacy against infection among these children fell to 12 percent at the end of January from 68 percent in mid-December compared to unvaccinated children. According to the studywhich have not been peer-reviewed.
For those ages 12 to 17, the vaccine’s protection against infection fell to 51 percent in late January from 66 percent in mid-December.
“These findings highlight the potential need to study alternative vaccine doses for children and the continuing importance of multi-layered protection, including wearing masks to prevent infection and transmission,” the researchers said.
The data showed the vaccine was 48 percent effective in keeping the younger age group out of the hospital, with a 73 percent effectiveness against hospitalization among teens last month.
This was less than 100 percent and 85 percent effective against hospitalization for both age groups as of mid-December.
Dr. Paul Offit, an expert in pediatric infectious diseases at Children’s Hospital of Philadelphia, wondered if the data was strong enough to say the vaccine’s efficacy has fallen dramatically, particularly against severe disease.
“It is not surprising that protection against mild disease is diminished,” Offit said. “We know that Omicron is a kind of immune evasion to protect against mild disease. The goal of the vaccine is to protect against severe disease – to keep children out of the hospital.”
Offit said the number of hospitalizations was too low for any real conclusions to be drawn, and that there was little information about why the children were hospitalized. He noted that protection from previous infection among the unvaccinated might also skew numbers.
“Natural infection can protect against serious diseases,” he said.
Younger children receive a lower dose of 10 mcg of the vaccine than children 12 to 17 years old, who receive the same 30 mcg dose as adults and are eligible for a third booster dose.
Pfizer said it is studying a three-dose schedule of the vaccine in children, noting that studies in adults suggest that “people vaccinated with three doses of the COVID-19 vaccine may have a higher degree of protection.”