In another twist in the debate about how best to protect children from the coronavirus, researchers reported Wednesday that Covid vaccines provided reduced protection from hospitalization in children as young as 12 during the latest Omicron surge.
However, the vaccine’s effectiveness against hospitalization remained consistent in children aged 5 to 11 years, and in adolescents aged 12 to 18 years, two doses of the vaccine remained highly protective against life-sustaining vital diseases.
But effectiveness against hospital admissions for less serious illnesses dropped to just 20 percent in these children. The results were published in The New England Journal of Medicine.
The data are broadly consistent with studies showing that the vaccines lost much of their effectiveness against Omicron variant infections in all age groups, but still prevented serious illness and death.
While any hospital stay is unnerving, it’s comforting to know that 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.
Among the teens in the study who were critically ill, 93 percent were unvaccinated, and most had at least one underlying condition, noted Dr. Patel fixed. “I think the big takeaway message is that with simple vaccination, you can prevent most critical diseases 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 were fully vaccinated. These percentages have hardly changed in recent months.
For some parents still debating vaccination, the apparent coronavirus retreat is complicating the decision. Cases and deaths have fallen to their lowest levels in a year, and no one knows yet if Omicron’s BA.2 subvariant will bring another wave.
Some parents, considering their children’s risk of Covid insignificant, were reluctant to vaccinate them from the start. But while children remain far less likely than adults to become seriously ill, many more of them were hospitalized during the Omicron surge than at any other time during the pandemic.
In the new study, the researchers analyzed medical records and interviewed parents of children aged 5 and older who were hospitalized for Covid. They excluded children who had tested positive for the coronavirus but had been hospitalized for other reasons.
Because relatively few children are hospitalized for Covid, the researchers were only able to identify 1,185 children and compare them to 1,627 others who did not have Covid. Among those hospitalized for Covid, 291 received life support and 14 died.
The study included data from 31 hospitals in 23 states and spanned July 1 to December 18, 2021, when the Delta variant was in circulation, and December 19 to February 17, when the Omicron variant was dominant. During the delta period, efficacy against hospitalization in adolescents was over 90 percent up to 44 weeks after vaccination.
However, during the Omicron surge, those numbers plummeted to about 40 percent for protection from overall hospitalizations, regardless of time since vaccination.
When the researchers analyzed the data by disease severity, they found that the vaccine’s effectiveness against critical illnesses in hospitalized adolescents remained high at 79 percent, but had fallen to 20 percent for less severe illnesses.
The new study is among the first to examine the effectiveness of vaccines in relation to disease severity in hospitalized patients. It’s possible this trend could also occur in adult patients when analyzed similarly, said Eli Rosenberg, associate director of science at the New York State Department of Health.
“This division between critical and non-critical is interesting,” he said. “It definitely adds a new layer.”
In children aged 5 to 11, full vaccination had an overall effectiveness of 68 percent against hospitalization. This data was collected during the Omicron wave because these children were not eligible for vaccination until November 2nd. There were too few to analyze efficacy by disease severity.
About 78 percent of all hospitalized adolescents in the study and 82 percent of younger children had one or more underlying conditions, such as obesity, autoimmune diseases, or breathing problems, including asthma.
The study suggests 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 validates the importance of vaccines for children as young as 5 and especially those who are immunocompromised or have pre-existing conditions,” she said.
The Omicron variant can partially evade immune defenses, so it’s not surprising that the vaccines didn’t do as well against the Delta variant, they and others said. Another recent study showed that in adolescents aged 12 to 17, two doses of the vaccine also offered virtually no protection against moderate disease caused by the Omicron variant. (Booster doses are now recommended for all Americans ages 12 and older.)
The wide discrepancy in vaccine effectiveness between those who were life-sustaining and those who weren’t may be due in part to the wide range of symptoms that children were hospitalized for. About one in four adolescents in the study required life support 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 that we saw were admitted — they were either very, very sick, or they were mostly admitted because they were infected and had a high fever or low oxygen saturation,” she said.
Parents also seemed more inclined to take young children to the hospital during the Omicron wave, added Dr. Vazquez added: “There are such concerns and fears about Covid.”
Some researchers have theorized that the decline in immunization protection among adolescents is due to declining efficacy over time—that is, adolescents may not have been as well protected during the omicron surge because too much time had passed since they were vaccinated .
However, the new study found that the vaccine’s effectiveness against the Omicron variant was 43 percent up to 22 weeks after immunization and 38 percent between 23 and 44 weeks. Falling immunity seemed less of a factor than the variant itself.
“It looked like it had more to do with Omicron,” said Dr. patel
Most of the vaccinated youth in the new study had only received two doses. There weren’t enough of those who received a third dose to rate its usefulness, but a previous study suggested that a booster shot dramatically improved protection against moderate disease in this age group, as it did in adults.
“I really think kids should get three doses, and I hope those numbers will go up,” said Akiko Iwasaki, an immunologist at Yale University. To date, only about 14 percent of children aged 12 and over have received a booster shot.