(CNN)The effectiveness of the Pfizer/BioNTech Covid-19 vaccines for children waned quickly during the Omicron surge, especially among children ages 5 to 11, but was still protective against severe disease, according to new data from the New York State Department of Health.
Within one month of being fully vaccinated, effectiveness of the Pfizer shots against infection caused by the Omicron variant fell from 68% to just 12% in the youngest children eligible to get the shots: those 5 to 11 years old.
Effectiveness against hospitalization in that age group was higher but also dropped substantially, falling from 100% in early December to just 48% by the end of January.
“The data are not surprising as the vaccine was developed in response to an earlier COVID-19 variant and reduced effectiveness of 2 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.
“It is critical to stress that vaccination is still recommended for everyone 5 years and older, including children 5-11. These data also demonstrate that COVID-19 vaccines reduce the risk of more severe illness and hospitalization for children 5-11, and I encourage parents and guardians to consult their pediatrician about getting their children vaccinated, and boosted if eligible, as soon as they can.”
Children 5 to 11 get a dose of the Pfizer vaccine that is 10 micrograms, one-third the dose given to children 12 to 17.
The study also found that while vaccine effectiveness also fell for older children and teens, it fell more slowly than it did for grade-schoolers. For any illness caused by Covid-19, vaccine effectiveness waned from 66% in early December to 51% by the end of January for kids 12 to 17. For hospitalizations, vaccine effectiveness fell from 85% to 73% over the same time frame.
The data was posted Monday as a preprint study on the medRxiv server. Preprints have not been reviewed by outside experts or accepted for publication in a medical journal.
The authors concluded that if other studies repeat these findings, the vaccine dose for younger children may need to be reviewed. The authors also said the data may demonstrate a need to continue “layered protections, including mask wearing, to prevent infection and transmission” in younger children.
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The US Centers for Disease Control and Prevention has been collecting its own data on vaccine effectiveness in children and is expected to release it soon.
“Pfizer and Moderna’s COVID-19 vaccines continue to offer high levels of protection against severe illness, hospitalization, and deaths in all age groups, despite decreased effectiveness against infection alone during the Omicron wave,” the agency said in a statement.
“CDC continues to monitor and evaluate data on vaccine effectiveness as it becomes available, but these vaccines work well and are the best tool we have to avoid severe outcomes.”
