COVID-19 vaccine less effective in children 5 to 11, CDC reports

March 1 (UPI) -- The Pfizer-BioNTech COVID-19 vaccine provides children ages 5 to 11 years with less protection against emergency room and urgent care facility visits related to virus symptoms compared to teens, according to federal data released Tuesday.

More than two months after receiving a second dose of the vaccine, children ages 5 to 11 years had 46% protection against needing emergency care for virus symptoms, data from the Centers for Disease Control and Prevention showed.

In comparison, teens ages 12 to 17 years had up to 83% protection against such healthcare encounters for the first five months after their second dose of the two-shot vaccine, the CDC said.

After more than five months, vaccine effectiveness declined to 38% for teens ages 12 to 15 years and to 46% for teens ages 16 and 17 years, the agency said.

However, it rebounded to 86% seven days or more after teens receive a third, booster dose, it said.

Teens ages 12 to 17 years given the Pfizer-BioNTech vaccine receive the same dose as adults for both shots, but children ages 5 to 11 years are given a dose that is about two-thirds smaller, according to the Food and Drug Administration.

In a separate analysis released Tuesday, fewer than 914 reports of side effects were submitted to the agency among just under 3,500 teens ages 12 to 17 years who received a booster dose of the vaccine between Dec. 9 and Feb. 20, according to the CDC.

Of these side effects, 92% were considered "non-serious," with the most common being dizziness, fainting and fever, the CDC said.

Myocarditis, or heart inflammation, was the most common serious side effect reported following receipt of the booster dose among teens ages 12 to 17 years, accounting for 47 of 77 cases, it said.

"These analyses also show that, similar to adults, protection against infection and emergency department and/or urgent care visits in children and adolescents who received a primary series declined when Omicron became predominant," the CDC said in a statement.

"Children and adolescents who were vaccinated with a primary series were still less likely to get infected than those who were unvaccinated, despite protection against infection declining during Omicron in these age groups," it said.

The Pfizer-BioNTech vaccine is the only one approved for use in the United States for children 17 years old and younger.

During the full study period, vaccine effectiveness against laboratory-confirmed COVID-19-associated hospitalization among children ages 5 to 11 years was 74% 14 to 67 days after the second dose and more than 90% among teens ages 12 to 17 years, the CDC said.

However, vaccine effectiveness against COVID-19-associated ER and urgent care visits was substantially lower after the Omicron variant of the virus became the most common one in circulation nationally, according to the CDC.

Children ages 12 to 17 years had "no significant protection" against needing urgent care for virus symptoms more than five months after receipt of the second dose of the vaccine, it said.

In adolescents ages 16 and 17 years, vaccine effectiveness during the Omicron predominant period increased to 81% seven days or more following administration of a third booster dose, the agency said.

Booster doses of the Pfizer-BioNTech vaccine have only been cleared for use in children age 12 years and older, according to the FDA.

The CDC figures are not the only ones to suggest lower vaccine protection among younger children.

Data released Monday by the public health researchers in New York State revealed that vaccine effectiveness against hospitalization during the Omicron variant surge declined from 85% to 73% for teens ages 12 to 17 years.

Among children ages 5 to 11 years, effectiveness fell from 100% to 48% during the Omicron surge, the data showed.

Vaccine effectiveness against testing positive declined from 66% to 51% among teens, and from 68% to 12% among younger children, the researchers from New York said.

The findings, which have not yet been peer reviewed, were released at a time when state officials announced plans to relax masking requirements in schools.

"COVID-19 vaccines continue to protect against severe illness, hospitalizations and deaths due to Omicron," the CDC said in its statement.

"CDC continues to recommend that all children and adolescents stay up to date on their COVID-19 vaccines, including a booster dose for eligible adolescents," it said.