Here’s how kids’ COVID vaccines are holding up in the real world amid omicron

New data on the real-world effectiveness of COVID-19 vaccines in children and teens largely mirrors what we’ve seen in adults so far: vaccine effectiveness is strong against the delta coronavirus variant but takes a significant hit when up against omicron. Time also erodes protection. But overall, the shots—particularly boosters—offer valuable protection against severe outcomes.

The data, published by the Centers for Disease Control and Prevention this week, drew on medical records from 10 states and only focused on vaccinations with the Pfizer-BioNTech vaccine. Researchers examined records of nearly 40,000 visits of non-immunocompromised children and teens to emergency departments and urgent care centers (ED and UC), as well as about 1,700 hospitalizations, all of which occurred between April 9, 2021, and January 29, 2022.

Expected waning

Across the delta and omicron eras, vaccine effectiveness of two doses against ED/UC visits was 83 percent in children 12 to 15, and 76 percent in teens 16 to 17. But those estimates only go up to five months after the two doses, and we know vaccine effectiveness wanes over time. After the five-month mark, those effectiveness estimates fell to 38 percent and 46 percent for ages 12 to 15 and 16 to 17, respectively.

In children ages 5 to 11, the overall effectiveness against ED/UC visits in the first five months after two doses was 46 percent. However, children in this age group were only eligible for vaccination starting in early November, significantly skewing the data in the omicron era. When researchers looked at vaccine effectiveness estimates just in the omicron era across all the age groups, they saw no significant differences. Specifically, omicron-era vaccine effectiveness for EC/UC visits in the first five months after two doses was 51 percent in children 5 to 11, 45 percent in children 12 to 15, and 34 percent in teens 16 to 17. On the other hand, in the delta-era-specific calculations, the effectiveness estimates were 92 percent for children 12 to 15 and 85 percent in teens 16 and 17.

A non-peer-reviewed pre-print study from researchers in New York was also released this week and purported to show that vaccine effectiveness in children ages 5 to 11 is lower than in older children who got a larger vaccine dose. The Pfizer-BioNTech vaccines for children 5 to 11 are 10 microgram doses, compared with the 30 microgram doses given to everyone 12 and older. The authors suggested that younger children may need larger doses in the future. However, this study did not control for immunocompromised status in children, and the finding has not borne out in this national data and other data sets collected by the CDC.

Still, other data from that New York study and the new CDC study generally reinforces what we already know about the vaccines—that the omicron variant—as well as time—can knock back effectiveness. This was particularly evident when the authors of the CDC study estimated the effectiveness against ED/UC visits after more than five months out from two doses and when children’s cases occurred in the midst of omicron. After five months, effectiveness against omicron ED/UC visits fell from 45 percent to -2 percent for children 12 to 15, and from 34 percent to -3 percent in teens 16 to 17.