The Pfizer three-dose vaccine would cover children 6 months to 4 years of age, while the Moderna two-dose vaccine would be for children 6 months to 5 years old. States have already ordered millions of doses. Depending on what the regulators are doing, White House officials have said the installments could begin in earnest on Tuesday. The FDA said clinical trial data from the companies showed that each vaccine met the safety and efficacy criteria in the age group. More than two years after the pandemic, no vaccine has been approved for children under 5 in the United States, an unmet need that has frustrated many parents. The FDA is expected to act immediately on the recommendations, followed by the Centers for Disease Control and Prevention later this week. The advisory committee voted 21-0 to propose the approval of the Moderna and Pfizer vaccines. “I know the mortality rate from Covid and young children may not be extremely high,” he said. Jay Portnoy, professor of pediatrics at Children’s Mercy Hospital in Kansas City, Mo. However, he said: “It is absolutely scary for parents for their child to get sick” or to be hospitalized. “There are so many parents who are absolutely desperate to get this vaccine,” he added, “and I think we have to give them the choice.” Both vaccines the panel considered Wednesday appear to be significantly less effective against symptomatic infection than adult vaccines when they were introduced. The FDA says Omicron is much more experienced in preventing vaccines from becoming infected than the original version of the virus. Given the decline in protection seen in adult recipients and the rapid progression of the virus, regulators said children receiving the Pfizer and Moderna vaccines would likely need a booster. This would mean that the Pfizer vaccine, developed with the German company BioNTech, could be completed in four doses, while Moderna’s in three. Both the Pfizer-BioNTech vaccine and the Moderna vaccine elicited levels of neutralizing or exclusive antibodies in children comparable to those in adolescents and young adults aged 16 to 25 years. The Pfizer vaccine has been approved for children ages 5 to 15 since last year, and regulators say it has helped prevent hospitalization and death. After two doses, the Pfizer vaccine was only about 28 percent effective in preventing symptomatic infection in children aged 6 months to 4 years. Pfizer has suggested that the vaccine was 80 percent effective after a third dose, but the finding was based on only 10 cases out of a subset of 1,678 participants in the trial. The test protocol stated that evaluations of vaccine efficacy were based on at least twice as many cases. The small number of cases on which the effectiveness finding was based was a matter of concern between committee members and regulators on Wednesday. Dr. Doran Fink, senior federal vaccine regulator, called Pfizer efficacy data preliminary. “We consider them inaccurate and potentially unstable,” he said. “Exactly how effective the vaccine is after the third dose needs further data.” Moderna found that its vaccine was 51 percent effective in preventing symptomatic infection in children aged 6 months to 2 years and 37 percent effective in children 2 to 5 years old. These results are consistent with those reported in adult studies during the Omicron era, the FDA said. However, vaccination continues to offer strong protection against a serious illness leading to hospitalization and death. Regulators and company employees spent part of the day discussing the side effects caused by vaccines. The vast majority were mild and tolerated by children in clinical trials: irritability and crying, drowsiness, fatigue and loss of appetite. Smaller participants in the trial had a fever, but these were consistent with the results of other pediatric vaccines.
In younger age groups, fevers may be more debilitating and require more urgent medical attention, a dynamic that puts significant pressure on manufacturers to properly calibrate the dose. Pfizer opted for a dose of just one-tenth the strength of the adult dose, given in three doses. The first two are given three weeks apart, with the third coming at least eight weeks after the second. Moderna used a quarter of its adult dose, administered in two shots, four weeks apart. Some difficult questions remain. Importantly, no vaccine has been tested against subtypes circulating in the United States. Clinical trials were largely carried out when the Omicron variant prevailed. Two variants, BA.4 and BA.5, could become dominant within a month. The need to protect these children from Covid is great, Dr. Peter Marks, the FDA’s top vaccine regulator, told the meeting. He added that hundreds of children had died from Covid, a percentage he said was “very comparable” to child deaths during a major flu outbreak in 2009 and 2010. .