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  • The Pfizer-BioNTech vaccine still offers strong protection against severe disease and hospitalization among younger school aged children.
  • But studies also show that the vaccines are not as effective at stopping children from developing COVID-19 from the Omicron variant.
  • A third shot may help add more protection against infection.

The Pfizer-BioNTech pediatric COVID-19 vaccine continues to protect children ages 5 to 11 from severe illness and hospitalization, two new studies show.

However, one of these studies suggests two doses don’t offer this age group much protection against infection caused by the Omicron variant, which is in line with what is seen in adults who have received only two doses.

Studies in adults suggest three doses of a COVID-19 vaccine offer stronger protection against infection caused by Omicron.

Dr. Christina Johns, pediatrician and senior medical adviser for PM Pediatrics, said the key point here is the protection offered by the vaccine against severe illness in kids.

“While it is always disappointing to see that things don’t work perfectly, there is no need to be concerned,” she said. “It is still very clear from the data that the vaccines are effective against severe disease, hospitalization, and death.”

On Feb. 28, scientists from the New York State Department of Health released non-peer-reviewed data on the effectiveness of two doses of the Pfizer-BioNTech COVID-19 vaccine in children and adolescents during the Omicron wave.

The results show a substantial decline in protection against infection after vaccination in children 5 to 11 years old. There was also a decline in protection against hospitalization, although less steep.

In this age group, the effectiveness of the vaccine against infection fell from 68 percent in mid-December to 12 percent by the end of January, researchers found.

Effectiveness against hospitalization fell from 100 percent to 48 percent over that period. However, so few children were hospitalized that this number is less reliable.

“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,” New York State Health Commissioner Dr. Mary Bassett said in a statement posted online.

In contrast, in 12- to 17-year-olds, researchers saw a less steep decline in protection against infection — falling from 66 percent in mid-December to 51 percent at the end of January.

Effectiveness against hospitalization for this age group fell from 85 percent to 73 percent during this period.

The study was published as a preprint on the server medRxiv, which means it has not been reviewed by independent scientists or published in a medical journal.

The Centers for Disease Control and Prevention (CDC) released data on March 1 that showed two doses of the Pfizer-BioNTech vaccine continue to offer strong protection against severe illness and hospitalization in children and adolescents.

During the time the Omicron variant was circulating, the effectiveness of two doses against emergency department or urgent care visits was 51 percent for children ages 5 to 11, say researchers.

For 12- to 17-year-olds, the effectiveness was between 34 and 45 percent.

Vaccination of the younger age group only began in November, so during the Omicron surge, they were more likely to be recently vaccinated.

With all COVID-19 vaccines, protection against infection and severe illness wanes the further after vaccination a person is.

Among 5- to 11-year-olds, vaccine effectiveness against hospitalization was 74 percent, according to researchers. However, as in the New York state study, so few children were hospitalized that this number is less reliable.

For adolescents, effectiveness against hospitalization was between 92 and 94 percent, falling to between 73 and 88 percent in adolescents vaccinated over 150 days earlier.

The study was published March 1 in the CDC’s journal Morbidity and Mortality Weekly Report.

The drop in protection against infection among 5- to 11-year-olds may stem from the fact that they receive one-third the dose that adolescents and adults receive.

Pfizer and BioNTech also tested a smaller dose of their vaccine in children under 5 years. After two doses did not produce a robust immune response, the companies began testing a third dose in this age group.

Children under age 5 are still not authorized to get a vaccine at this point.

Experts also caution that more research is needed to know whether the results seen in the New York state study are true in other populations.

“We typically do not change the way we practice medicine based on one or two studies,” said Johns.

“So we need to look at more data, and data over a longer period,” she added. “Was this a dosing issue? Was it a dosing interval issue? Was it an immune escape issue because of Omicron?”

Dr. Tammy Lundstrom, an infectious disease specialist and chief medical officer at Trinity Health, said given the strong protection offered by the vaccines against infection in 5- to 11-year-olds, she still recommends parents have their children vaccinated.

“We will know with time whether further boosters are needed to optimize protection,” she said.

The CDC has not yet recommended booster doses for this age group.

Johns said another thing to keep in mind is that, in 12- to 18-year-olds, the Pfizer-BioNTech vaccine has been found to reduce the risk of multisystem inflammatory syndrome in children (MIS-C).

This potentially serious inflammatory condition can occur after infection with the coronavirus that causes COVID-19.

Data is not yet available on whether the vaccine reduces the risk of MIS-C in younger children, but this is another potential benefit of vaccinating this younger age group.

Lundstrom also recommends that parents use the CDC’s updated guidelines when deciding whether their child should wear a mask in indoor public settings. These can be found on the agency’s website.

In addition, “it’s important, as always, to stay home if ill, and get tested early if symptoms of COVID infection are present,” she said.