January 10, 2024
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Key takeaways:
- The vaccine had a reported 98.4% efficacy during the delta wave.
- Vaccine efficacy also lasted for 4 months before stabilizing.
COVID-19 vaccination provided strong and durable protection among children and adolescents during two strong waves of infections, according to real-world study findings reported in Annals of Internal Medicine.
The study assessed the effectiveness of Pfizer-BioNTech’s COVID-19 vaccine, which first became available for older adolescents in December 2020 and then for younger children throughout the next year.
COVID-19 vaccination provided durable protection among children during two particularly difficult waves of the virus. Image: Adobe Stock.
Christopher B. Forrest
“What we didn’t know was whether the vaccine was effective in real-world settings, like primary care physicians’ offices or hospitals,” Christopher B. Forrest, MD, PhD, director of the Applied Clinical Research Center and PEDSnet at The Children’s Hospital of Philadelphia, told Healio. “We knew that the vaccine had had good efficacy against the delta virus, but there was less information about how it would perform against the omicron variant of the virus.”
Forrest said durability was also a question mark, with a lack of “good information” about the extent of the vaccine’s effectiveness.
“I lead a network of health systems that share electronic health record data for about 10% of all children in the United States. It’s called PEDSnet, and that became a really rich data source for us to evaluate the vaccine effectiveness,” Forrest said.
Updated monovalent COVID-19 vaccines have been recommended for all ages since this past September. Forrest said studying an older version of the vaccine does provide valuable insight.
“The strength of the messenger RNA technology is that it can be rapidly adapted to changing viral variants,” Forrest said. “I felt families and parents making decisions (about vaccination) would benefit from not just the clinical trials, which are now kind of old, but an ongoing assessment of how this vaccine is working. Unfortunately, there’s vaccine hesitancy out there, and the more we can allay concerns about the safety of the vaccine in large scale populations, the better.”
The researchers studied PEDSnet data on nearly 250,000 children and adolescents — a cohort 100 times larger than the clinical trials, which included around 2,500 participants, Forrest noted. The participants included 77,392 adolescents (58% vaccinated) during the delta wave, and 111,539 children (45% vaccinated) and 56,080 adolescents (38% vaccinated) during the omicron wave.
Over the course of the delta period, the authors estimated the effectiveness of the Pfizer vaccine to be 98.4% (95% CI, 98.1%-98.7%) against a documented infection among adolescents. During omicron, the estimated effectiveness against documented infection among children was 74.3% (CI, 72.2%-76.2%). Estimated effectiveness against a documented omicron infection was 85.5% (CI, 83.8%-87.1%), and declined 4 months after inoculation before stabilizing.
Forrest said the durability of the vaccine was particularly surprising.
“There was some sort of bias out there among my colleagues in pediatrics that the vaccine was pretty good for the first 6 months, but then it tends to tail off after that,” Forrest said. “What we found is that the vaccine effectiveness did decrease at 4 months, but then it persisted for at least a year, so that there was adequate protection for a whole year, which is now consistent with [the] thinking that we’re probably going to boost people every year, just like flu.”
From a public health perspective, the results show “adequate levels of protection with the older vaccines,” he said.
“This is a study that demonstrates that the vaccines delivered by primary care physicians are very effective … and they’re safe,” Forrest said.
References:
Real-world analysis: COVID-19 vaccine strongly effective for children and adolescents during delta and omicron. https://www.eurekalert.org/news-releases/1030472. Published Jan. 8, 2024. Accessed Jan. 10, 2024.
Wu Q, et al. Ann Intern Med. 2023;doi:10.1101/2023.06.16.23291515.
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Sources/Disclosures
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Disclosures:
Forrest reports receiving grants from the NIH and Patient Centered Outcomes Research Institute to fund parts of this work. Please see the study for all other authors’ relevant financial disclosures.
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