New study on Covid-19 vaccine effectiveness in kids

March 10, 2022

Kids & COVID Vaccines

New research raises important questions about the COVID-19 vaccine in children ages 5-11.
What To Know & Why It Matters.


  • Dec. 2020: The FDA grants emergency use authorization (EUA) for the Pfizer COVID-19 vaccine for Americans ages 16 and older.
  • May 2021: The FDA grants EUA for the Pfizer COVID-19 vaccine for kids ages 12-15.
  • Oct. 2021: The FDA grants EUA for ages 5-11 for one-third the dose of the typical Pfizer COVID vaccine.
  • Important: The CDC confirmed the first case of the highly contagious Omicron variant in the U.S. on December 1, 2021.

New Study:

  • The New York State Dept. of Health analyzed COVID-19 data from 360,000+ vaccinated kids ages 5-11 and from 850,000+ vaccinated kids ages 12-17 during the Omicron surge (between mid-Dec. 2021 through the end of January 2022).
  • Results: Vaccine efficacy against infection and hospitalization dropped for both age groups, but data reflected a more pronounced decline in those in the younger age group.

"The striking difference between 11- and 12-year-olds can only be explained by the three-fold dosing reduction in the younger children. The one-year age difference is highly unlikely to make any other factor relevant."

Virologist John Moore, Weill Cornell Medical College, who (along with the study’s authors) suggests the lower vaccine effectiveness observed in kids ages 5-11 is likely due to the lower dose given to this age group. The “striking difference” in efficacy was especially observed between those ages 11 and 12 during the last week of January.

Something To Consider

  • We don’t know preexisting conditions for hospitalized vaccinated/unvaccinated children.
  • Younger children in this study had more recently been vaccinated (a median of 51 days vs. more than 200 days for older kids).
  • The study incl. a high % drop in efficacy vs. hospitalization for younger kids (100% – 48%), but a closer look at the numbers shows that out of hundreds of thousands of kids ages 5-11, 13 vaccinated children and 166 unvaccinated were hospitalized overall.

Why It Matters:

  • A recent CDC study echoes the NY State Health Dept. results — a much *smaller* sample size from AZ, FL, UT and TX shows a drop in vaccine efficacy vs. Omicron.
  • Recent data shows fewer vaccinated children were hospitalized or received medical care than unvaccinated.
  • Big Picture: Serious cases (even w/Omicron, & with some children vaccinated, others not) remain rare: “In states reporting, 0.00%-0.01% of all child COVID-19 cases resulted in death.” (American Academy of Pediatrics).

The authors of the NY State Health Dept.’s study say their findings “highlight the potential need to study alternative vaccine dosing for children …” More than 100 COVID vaccine trials continue. For available vaccines, we don’t even have a year’s worth of data for the group under the age of 16.

Meanwhile, Pfizer floated the idea for a second booster dose for some adults (something Moderna recently requested in EUA), and vaccine trials for those 6 months – 4 years old continue after a lower dose did not produce the efficacy desired.

Click HERE for the study from the New York State Department of Health

Click HERE for the recent study from the CDC

Pfizer Shot Is Far Less Effective in 5- to 11-Year-Olds Than in Older Kids, New Data Show (The New York Times)

Vaccine info. on kids: Summary of data publicly available reported by the Centers for Disease Control and Prevention (American Academy of Pediatrics)

Children and COVID-19: State-Level Data Report (American Academy of Pediatrics)

Pfizer Covid vaccine is less effective in kids 5 to 11, study finds (STAT)

by Jenna Lee,