In yet another twist on the debate over how best to protect children from the coronavirus, researchers reported on Wednesday that Covid vaccines offered reduced protection against hospitalization in children aged 12 and older during the latest Omicron wave.
The efficacy of the vaccine against hospitalization remained stable in children aged 5 to 11 years, however, in adolescents aged 12 to 18 years, two doses of the vaccine remained highly protective against critical illness requiring life support.
But effectiveness against hospitalization for minor illnesses fell to just 20 percent in these children. The findings were published in The New England Journal of Medicine.
The data is broadly consistent with studies showing that the vaccines lost much of their potency against infection with the Omicron variant in all age groups, but still prevented serious illness and death.
While any hospitalization is nerve-wracking, it’s reassuring that the vaccines still protected children from the worst effects of infection, said Dr. Manish Patel, a researcher at the Centers for Disease Control and Prevention who led the study.
Of the adolescents in the study who were critically ill, 93 percent had not been vaccinated, and most had at least one underlying condition, Dr. Pat up. “I think the big message is that with the simple act of vaccination you can prevent the most critical illness in most children,” he said.
As of March 23, in the United States, only about one in four children ages 5 to 11 and just over half of youth ages 12 to 17 had been fully vaccinated. Those percentages have barely increased in recent months.
For some parents who are still debating vaccination, the decision is complicated by the apparent coronavirus withdrawal. Cases and deaths have fallen to their lowest level in a year and no one knows yet if Omicron’s BA.2 sub-variant will bring another wave.
Some parents, who believed that the risk of Covid to their children was insignificant, were reluctant to vaccinate them from the start. But while children are much less likely than adults to become seriously ill, far more of them were hospitalized during the Omicron wave than at any other time during the pandemic.
In the new study, the researchers analyzed medical records and interviewed parents of children ages 5 and older who had been hospitalized for Covid. They excluded children who tested positive for the coronavirus but were hospitalized for other reasons.
Because relatively few children are hospitalized for Covid, the researchers were only able to identify 1,185 children, compared with 1,627 others who did not have Covid. Of those hospitalized for Covid, 291 received life support and 14 died.
The study included data from 31 hospitals in 23 states, and ran from July 1 to December 18, 2021, when the Delta variant was in circulation, and from December 19 to February 17, when the Omicron variant was dominant. During the Delta period, the effectiveness against hospitalization was more than 90 percent in the adolescents up to 44 weeks after vaccination.
However, during the Omicron peak, those numbers plummeted to about 40 percent for protection against hospitalization in general, regardless of the time since vaccination.
When the researchers analyzed the data for disease severity, they found that vaccine efficacy against critical illness among hospitalized adolescents remained high, at 79 percent, but had fallen to 20 percent for minor illnesses.
The new study is one of the first to look at vaccine effectiveness in relation to disease severity in hospitalized patients. It’s possible that this trend would also occur in adult patients, if they were analyzed in the same way, said Eli Rosenberg, deputy director for science at the New York State Department of Health.
“This split between critical and non-critical is interesting,” he said. “This definitely adds another layer.”
In children aged 5 to 11 years, complete vaccination had a 68 percent effectiveness against hospitalization overall. That data was collected during the Omicron peak, because these children only became eligible for vaccination on November 2. There were too few to analyze effectiveness by disease severity.
About 78 percent of all hospitalized adolescents in the study, and 82 percent of the younger children, had one or more underlying medical conditions, such as obesity, autoimmune disorders or breathing problems, including asthma.
The study suggests that the vaccine protected a majority of these children from the worst outcomes, said Dr. Luciana Borio, a former acting chief scientist at the Food and Drug Administration.
“It really reaffirms the importance of vaccines for children ages 5 and older, and especially for those who are immunocompromised or have underlying medical conditions,” she said.
The Omicron variant can partially evade immune defenses, so it’s not surprising that the vaccines didn’t fare as well as they did against the Delta variant, they and others said. Another recent study found that in adolescents aged 12 to 17 years, two doses of the vaccine also provided virtually no protection against moderate illness caused by the Omicron variant. (Booster doses are now recommended for all Americans ages 12 and older.)
The large discrepancy in vaccine efficacy between those who needed life support and those who did not may be due in part to the wide range of symptoms for which children were hospitalized. About one in four adolescents in the study required life-sustaining interventions, such as mechanical ventilation or extracorporeal membrane oxygenation.
dr. Marietta Vazquez, an infectious disease specialist at Yale School of Medicine who was not involved in the study, said that, in her experience, most children hospitalized during the Omicron wave recovered quickly.
“The kids we saw admitted — they were either very, very sick, or they were usually admitted because they were infected and they had a high fever or they had low oxygen saturation,” she said.
Parents also seemed more likely to take young children to the hospital during the Omicron wave, added Dr. Vazquez added: “There is so much concern and fear about Covid.”
Some researchers have theorized that the decline in vaccine protection in adolescents was the result of declining effectiveness over time — that is, adolescents may not have been as well protected during the Omicron wave because too much time had passed since their vaccination. immunizations.
But the new study found that vaccine efficacy against the Omicron variant was 43 percent up to 22 weeks after immunization and 38 percent between 23 and 44 weeks. Declining immunity turned out to be less of a factor than the variant itself.
“Looks like it was more Omicron-related,” said Dr. patella.
Most of the vaccinated adolescents in the new study had received only two doses. There weren’t enough of those who received a third dose to evaluate its benefit, but a previous study suggested that a booster shot dramatically improved protection against moderate disease in this age group, just as it did in adults.
“I really think kids should get three doses, and I’m hoping this number will go up,” said Akiko Iwasaki, an immunologist at Yale University. So far, only about 14 percent of children ages 12 and older have received a booster dose.