Albany, NY—Early in February, it looked as if the COVID-19 vaccines for children aged younger than 5 years was going to receive fast-track FDA approval.

However, the FDA was notified by Pfizer that new data had recently emerged regarding its Emergency Use Authorization request for the use of the Pfizer-BioNTech COVID-19 vaccine in children aged 6 months through 4 years. Based on the new data, the FDA postponed the Vaccines and Related Biological Products Advisory Committee meeting originally scheduled for February 15, 2022, so that additional data could be reviewed.

Now, a new preprint study is raising questions about how beneficial the Pfizer vaccine was in the older group aged 5 to 11 years. A study assessing the vaccine in children in New York points out that protection against the Omicron variant "declined rapidly," although they said it was protective against severe disease. New York State Department of Health researchers, who conducted the study, said they still recommended vaccination in that age group.

Noting limited evidence on the effectiveness of the vaccine for children, especially those aged 5 to 11 years, and after the Omicron variant's emergence, the authors sought to estimate the Pfizer vaccine's effectiveness against COVID cases and hospitalizations among those children and the children aged 12 to 17 years cohort between December 2021 and January 2022.

Data about the New York state children aged 5 to 17 years were obtained from statewide immunization, laboratory testing, and hospitalization databases. Researchers tracked new laboratory-confirmed COVID-19 cases and hospitalizations, while calculating the incidence rate ratio (IRR) and comparing outcomes by vaccination status as well as estimated vaccine effectiveness (VE: 1-[1/IRR]).

The participants included 852,384 fully vaccinated children aged 12 to 17 years and 365,502 children aged 5 to 11 years.

Results from December 13, 2021, to January 30, 2022, indicated that VE against cases declined from 66% (95% CI: 64%, 67%) to 51% (95% CI: 48%, 54%) for those aged 12 to 17 years and from 68% (95% CI: 63%, 72%) to 12% (95% CI: 6%, 16%) for those aged 5 to 11 years.

"During the January 24-30 week, VE for children 11 years was 11% (95% CI: -3%, 23%) and for those age 12 was 67% (95% CI: 62%, 71%)," the authors advised. "VE against hospitalization decline changed from 85% (95% CI: 63%, 95%) to 73% (95% CI: 53%, 87%) for children 12-17 years, and from 100% (95% CI: -189%, 100%) to 48% (95% CI: -12%, 75%) for those 5-11 years."

The study noted that, among children newly fully vaccinated December 13, 2021, to January 2, 2022, VE against cases within 2 weeks of full vaccination for children aged 12 to 17 years was 76% (95% CI: 71%, 81%) and by 28 to 34 days it was 56% (95% CI: 43%, 63%). It was even more dramatic for children aged 5 to 11 years—VE against cases declined from 65% (95% CI: 62%, 68%) to 12% (95% CI: 8%, 16%) by 28 to 34 days.

"In the Omicron era, the effectiveness against cases of BNT162b2 declined rapidly for children, particularly those 5-11 years," researchers concluded. "However, vaccination of children 5-11 years was protective against severe disease and is recommended. These results highlight the potential need to study alternative vaccine dosing for children and the continued importance layered protections, including mask-wearing, to prevent infection and transmission."

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