Addressing COVID-19 Vaccine Efficacy Challenges in Younger Children

The Pfizer-BioNTech COVID-19 vaccine's effectiveness in the younger populations have run into some challenges of late. On February 11, Pfizer-BioNTech postponed their Food and Drug Administration application for their COVID-19 vaccine, BNT162b2, in children who are 6 months to 4 years of age. The companies stated the need to review more data for their deferment.

Then, earlier this week, a study that was published in a preprint showed that the BNT162b2 vaccine had greatly diminished efficacy and protection against infection within 28-34 days after full vaccination.

“From December 13, 2021 to January 30, 2022, among 852,384 fully-vaccinated children 12-17 years and 365,502 children 5-11 years, [vaccine effectiveness] VE against cases declined from 66% (95% CI: 64%, 67%) to 51% (95% CI: 48%, 54%) for those 12-17 years and from 68% (95% CI: 63%, 72%) to 12% (95% CI: 6%, 16%) for those 5-11 years,” the investigators wrote in their preprint.

Peter Hotez, MD, PhD, dean for the National School of Tropical Medicine, Baylor College of Medicine, and co-director of the Center for Vaccine Development at Texas Children’s Hospital, says that the drop off in the 5-11 year old population may be a direct result of the amount of antigen being delivered in the vaccines.

“The dose went from 30 micrograms [12-17 year old dosage] to 10 micrograms [5-11 year old dosage], so I think there is a good possibility a lot of this is dose-dependency,” Hotez said.

Hotez explains there is “flexibility” built into the system to address the vaccine effectiveness, including upping the dosage in each vaccine or administering a booster dose.

“Can you do some additional dose-ranging studies in the younger kids to fix that—maybe don’t go so dramatically down from 30 to 10 but go to something in-between that and would that fix the problem? Or maybe the easiest thing is to give a booster.”

He said the booster dose helped the 12-17 year old group return to higher immunity levels.

As the case loads continue to come down in the United States, and the CDC changed its mask guidance last week, the question becomes what is next for the virus?

Hotez does see the pandemic evolving and its behavior is demonstrating a more episodic phase and not necessarily an endemic phase. However, he says we need to remain vigilant.

“We may get a breather or a pause, but the question is what does that pause look like? Is it going to be 6 weeks, 6 months, or longer? I personally think we should watch out what happens in the summer because of 2020 and 2021. We saw a terrible surge across the southern states and in Texas and we should anticipate that again.” 

Contagion spoke to Hotez about dose-dependency in m-RNA vaccines, his continued belief in the vaccines in the 5-11 year old population, and his perspective on COVID-19’s next phase.