The Pfizer-BioNTech-made coronavirus vaccine is far less effective at preventing infection in children ages 5 to 11 than in older adolescents or adults, according to a large new set of data collected by New York state health officials — a finding that has profound implications. for these children and their parents.
The Pfizer vaccine is the only Covid injection approved for that age group in the United States. It still prevents serious illness in the children, but offers virtually no protection against infection even within a month of full immunization, data collected during the Omicron peak suggest.
The sharp decline in vaccine performance in young children may be due to them receiving one-third the dose given to older children and adults, researchers and federal officials who reviewed the data.
The findings, posted online Monday, follow results of clinical trials indicating the vaccine fared poorly in children ages 2 to 4, who were given an even smaller dose.
Experts feared the news would discourage hesitant parents from vaccinating their children. Other studies have shown that the vaccine was also not potently protective against infection with the Omicron variant in adults.
“It’s disappointing, but not entirely surprising, given that this is a vaccine that was developed in response to an earlier variant,” said Eli Rosenberg, deputy director of science at the New York State Department of Health, who led the study. “It looks very disturbing to see this rapid decline, but it’s all against Omicron again.”
Still, he and other public health experts said they recommend the injection for children, given the protection against serious illness even shown in the new dataset.
“We have to make sure we emphasize the donut and not the hole,” says Dr. Kathryn M. Edwards, a pediatric vaccine expert at Vanderbilt University.
In their research, Dr. Rosenberg and colleagues collected data from 852,384 newly fully vaccinated children ages 12 to 17 and 365,502 children ages 5 to 11 between December 13, 2021 and January 31, 2022, the height of the Omicron Gulf.
The vaccine’s effectiveness against hospitalization fell from 85 percent in the older children to 73 percent. In the younger children, the effectiveness fell from 100 percent to 48 percent. But because few children were hospitalized, these estimates have large margins of error.
The numbers for protection against infection are more reliable. The effectiveness of the vaccine against infection in the older children decreased from 66 percent to 51 percent. But in the younger children, it dropped sharply to just 12 percent from 68 percent.
The numbers change drastically between the ages of 11 and 12. In the week ending Jan. 30, the vaccine’s effectiveness against infection was 67 percent in 12-year-olds, but only 11 percent in 11-year-old children.
“The difference between the two age groups is striking,” said Florian Krammer, an immunologist at the Icahn School of Medicine at Mount Sinai.
The biological difference between the two ages is likely minimal, but while 12-year-old children received 30 micrograms of the vaccine — the same dose given to adults — children aged 11 received only 10 micrograms, he noted.
“This is super interesting because it would almost suggest that it’s the dose that makes the difference,” he added. “The question is how to solve that.”
There have been at least 851 deaths from Covid-19 in children under 17 and nearly 7,000 cases of multisystem inflammatory syndrome in children, a rare but serious condition linked to Covid. More children were hospitalized during the Omicron peak than at any other time in the pandemic.
The findings underscore the need to gather more information about the best dose, number and timing for the injections given to children, said Dr. Rosenberg. They also underline vaccines as just one measure of protection against the virus, along with masks and social distancing, he said.
The research of Dr. Rosenberg was published just days after the Centers for Disease Control and Prevention issued new recommendations that would stop the majority of Americans from wearing masks, including in schools.
The new data also raise important questions about the Biden administration’s strategy for vaccinating children. Only about one in four children ages 5 to 11 have received two doses of the vaccine. (The CDC has not yet recommended booster doses for this age group.)
The vaccine is not yet approved for children under the age of 5. Scientific advisers to the Food and Drug Administration were set to meet on Feb. 15 to evaluate two doses of the vaccine for the youngest children, while three doses were still being tested. But the meeting was postponed after Pfizer submitted additional data indicating that two doses were not highly protective against the Omicron variant of the virus.
dr. Rosenberg briefed senior CDC officials, including Dr. Rochelle P. Walensky, the agency’s director, with findings. FDA leaders learned of the data around the same time. Some federal scientists insisted that the data be made public ahead of the FDA expert meeting scheduled for Feb. 15, considering it highly relevant to the discussion of dosing in children under 5, said federal officials and others who were familiar with their reactions to it.
The data is generally consistent with a report from Britain showing that vaccine efficacy against symptomatic infection in adolescents aged 12 to 17 falls to 23 percent after two months. The CDC has compiled its own data on the vaccine’s effectiveness in younger children and is expected to release some of it as early as this week, according to people familiar with the agency’s plans.
Israeli researchers have also been assessing the vaccine’s performance in young children since the country made it available to them in November.
“We will continue to study and review real-world data from the vaccine,” said Amy Rose, a Pfizer spokeswoman, in response to questions about the new data.
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dr. Philip Krause, who recently retired from the FDA as a senior vaccine regulator, said assumptions about certain antibody levels that are predictive of vaccine effectiveness should be re-evaluated in light of the new results.
“It certainly weakens the argument for forcing people to get that lower dose,” he said.
It’s not uncommon for experts to rethink the dosage and interval for pediatric vaccines as more evidence becomes available. But in this case, giving the children a higher dose to boost the immune response may not be an option, as some data suggests it can cause too much fever, an unwanted and potentially dangerous side effect in young children.
There are other alternatives that can improve immunity in young children, said Deepta Bhattacharya, an immunologist at the University of Arizona.
Pfizer and BioNTech are testing a third dose in children under the age of 5 and in children aged 5 to 11, with the idea that, as in adults, an additional injection could significantly boost immunity. The results of these trials are expected in a few weeks. Studies in adults suggest that three doses of the vaccine were more protective against the Omicron variant than two doses.
dr. Bhattacharya said he and his wife have spaced the two doses for their children, who are 8 and 10, eight weeks apart instead of the currently recommended three, based on studies suggesting longer intervals between doses may increase protection. improve. The CDC last week encouraged some people over the age of 12, especially boys and men between the ages of 12 and 39, to wait eight weeks between the first and second injection.
Another option could be a version of the vaccine designed to thwart the Omicron variant, or a version with a combination of several variants. Pfizer-BioNTech, Moderna, and Johnson and Johnson are all testing Omicron-specific versions of their vaccines.
The next variant can be very different from Omicron, just like Omicron did from the Delta variant. But training the body to recognize multiple versions would still provide a better chance of avoiding infection with newer forms of the virus. “Deciding when and how best to update these vaccines I think is still the most important conversation that’s going to take place here,” said Dr. Bhattacharya.
Newer vaccines that use different approaches than the vaccines currently approved in the United States may also work better for children. A protein-based vaccine made by Novavax is currently under review by the FDA, and pharmaceutical companies Sanofi and GSK said this month they plan to submit their vaccine for evaluation soon.
Many parents want to vaccinate their children to avoid spreading the virus to vulnerable relatives, to keep them in school or to avoid the possibility of long-term Covid, the poorly understood set of persistent symptoms that can occur even after a mild infection. Experts recognized that the vaccine’s low effectiveness against infection does not allay those concerns.
Still, the vaccines provide “more protection than we think,” said Jessica Andriesen, a vaccine data expert at the Fred Hutchinson Cancer Research Center in Seattle.
“They can also make sure that your child who brings Covid home doesn’t shed as many viruses as they would if they weren’t vaccinated, and they can also have it for a shorter amount of time,” she said.
The virus is here to stay, and children’s risk of serious consequences increases with age. So vaccinating children early is a good idea, says Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia and advisor to the FDA.
“The argument I make to parents when I talk to them about this vaccine is that your children will grow up,” he said. “They will have to be protected from this virus for years.”
Sharon LaFraniere and Isabel Kershner reported.
