Vaccination protection against moderate disease among adolescents has decreased,

Five months after immunization, the two doses of Pfizer-BioNTech vaccine appeared to offer virtually no defense against moderate disease caused by the Omicron variant, as measured by visits to emergency rooms and urgent care clinics. Data released on Tuesday by the Centers for Disease Control and Prevention.

But booster shots have greatly increased protection and bolstered the agency’s recommendation of booster shots for anyone aged 12 and over.

Findings should be interpreted with caution. The agency’s study did not exclude unvaccinated adolescents who were immune to a previous infection, which could make the vaccination seem less effective than it was.

And the researchers presented only limited data on hospitalizations, a more reliable surrogate for serious illness than emergency room and emergency care visits.

“A limitation of these data is that parents may bring their children to emergency care or the emergency room for a variety of reasons, and the efficacy of the vaccine has not yet been studied with an immunocompromised condition, underlying health condition, or vaccine product,” the CDC said. Said. In a statement.

A few studies have shown that although vaccine efficacy against infection declines over time, the immune response remains extremely protective against hospitalization and death, even against the highly contagious Omicron variant.

A separate analysis of data from 29 jurisdictions published on the CDC’s website reported nine Covid-related deaths among vaccinated children and adolescents aged 5 to 17 years between early April 2021 and January 2022, while 121 deaths were reported in unvaccinated children at that age. .

Still, the findings suggest that scientists should carefully monitor vaccine performance over time in children and adolescents, bearing in mind that vaccines may be necessary.

“We need to see more of these studies to see if this is consistent,” said Deepta Bhattacharya, an immunologist at the University of Arizona. “But I think it’s likely, and as parents we have to be prepared for this to take another chance.”

The results are particularly important to parents as school districts across the country consider ending mask mandates. Last week, the CDC released new guidance suggesting that nearly 70 percent of Americans can safely leave their masks indoors in public.

Vaccine uptake among young children has been slow; Less than one in four children aged 5 to 11 are now fully vaccinated. More than half of adolescents aged 12 to 17 were fully vaccinated with two shots, and about 12 percent received a third booster dose.

The findings follow data released Monday showing two doses being offered. little protection against infection with the Omicron variant in children aged 5 to 11 years after only one month. The vaccine has been shown to provide reduced protection against infection, particularly against the Omicron variant, even in adults. new data published by the CDC website reflects this trend.

In the new study, the researchers analyzed data on 39,217 visits to emergency rooms and emergency care clinics and 1,699 hospitalizations among children ages 5-17 in 10 states from April 9, 2021 to January 29, 2022.

In children aged 5 to 11 years, the vaccine’s ability to prevent moderate disease dropped to 46 percent about two months after full vaccination (two weeks after the second vaccine). Most visits to emergency rooms and urgent care clinics occurred during the Omicron surge, when older children and adults were also more vulnerable than they were before the pandemic.

During the delta period, the efficacy of the vaccine against moderate disease in adolescents remained stable. But 150 days after full vaccination, efficacy dropped sharply to 38 percent in 12- to 15-year-old adolescents and 46 percent in 16- and 17-year-olds.

When the researchers analyzed the data for protection specifically during the Omicron period, protection against moderate disease was almost completely absent in adolescents vaccinated more than 150 days ago. But a third dose of vaccine brought efficacy back to 81 percent.

The findings are consistent with studies in adults, which showed that the efficacy of the vaccine against infection and mild illness declined sharply over time, particularly after the arrival of the Omicron variant.

Efficacy is a comparison between protection in vaccinated and unvaccinated groups of people. However, Paul Offit, director of the Vaccine Education Center at Children’s Hospital in Philadelphia and consultant to the Food and Drug Administration, said that as more people in the population become immune through the infection, it becomes harder to get a true picture of vaccine effectiveness.

“Are we comparing apples to apples when we say that vaccine efficacy has decreased?” said.

It was still harder to parse protection against severe disease. Young children had too few hospitalizations to draw firm conclusions. Among adolescents vaccinated more than 150 days ago, efficacy against severe disease remained strong at 70 percent or higher.

However, most of these hospitalizations occurred during the Delta period, so the data do not provide a window into efficacy against hospitalization as the Omicron variant comes and goes.

The CDC recommends booster shots for Americans 12 years and older. Pfizer and BioNTech evaluate the benefit of the third dose in young children.

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