Samantha Castaneda, 10, received her first dose of the Pfizer vaccine in San Francisco last year. Credit … Mike Kai Chen for The New York Times
A booster injection of Covid vaccine by Pfizer-BioNTech has increased the level of neutralizing antibodies against both the original version of the virus and the Omicron variant in a small experiment in children aged 5 to 11, the companies said Thursday.
If companies’ claims of a strong immune response are approved by federal regulators, the government could extend eligibility for booster doses to include another 28 million children.
The Pfizer and BioNTech study, which the companies described in a brief news release, included 140 children who received a booster dose six months after their second injection.
Children showed a sixfold increase in antibody levels against the original version of the virus one month after receiving the booster vaccine, compared with one month after receiving the second dose. Laboratory tests on 30 blood samples also showed 36 times higher levels of neutralizing antibodies against the Omicron variant than levels after just two doses, according to a press release and a Pfizer spokesman.
The companies said they would ask the Food and Drug Administration for emergency permission for a booster dose for 5- to 11-year-olds “in the coming days”. The Agency shall normally act within one month of receiving such requests.
At present, everyone aged 12 and over in the United States qualifies for at least one booster dose, and about 30 million people aged 50 and over qualify for a second dose. Studies show that 5- to 11-year-olds may need a booster dose in particular.
Researchers in New York recently found that while two injections of the Pfizer vaccine protect children in this age group from serious illness, they provide virtually no protection against symptomatic infection, even just a month after full immunization.
The announcement of the companies comes as the cases increase slightly again after two months of prolonged decline. The rise is particularly noticeable in the northeast, where sub-option BA.2, now the dominant version of the virus in the United States, first emerged.
Dr Anthony C. Fauci, President Biden’s chief medical adviser, warned in recent days that the nation could see a significant increase in infections over the next few weeks. But he said the hospitalization rate is unlikely to rise at the same time because so many Americans have some immunity, whether from vaccines or previous infections.
Several hundred children between the ages of 5 and 11 have died from Covid since the beginning of the pandemic, according to the Centers for Disease Control and Prevention, but pediatric vaccines have been difficult to sell to many parents. Only about 28 percent of children in this age group received two doses and would qualify for a booster. Nearly 7 percent received only one dose, according to the agency.
Vaccines were initially rushed after they were proposed for this age group in November, but the increase in vaccination rates has since slowed to a creep. In the last month, for example, it has risen by one percentage point.
The proportion of children aged 5 to 11 with at least one dose varies considerably from region to region, according to a study by the Kaiser Family Foundation. Five of the top 10 states with the highest vaccination rates are in New England, while eight of the 10 states with the lowest vaccination rates are in the South.
Although more than 250 million Americans have been safely vaccinated since the pandemic began, pediatric experts say many parents fear unknown consequences for their children. Compared to decades-old vaccines to protect against measles, mumps and other diseases, Covid vaccines are brand new.
A study by New York researchers published online in late February found that for children aged 5 to 11, the effectiveness of the Pfizer vaccine against infection dropped to 12 percent from 68 percent within 28 to 34 days after the second dose.
This is a sharper decline than in older adolescents and teenagers, who received a much stronger dose. Some experts suggest that the dose difference explains the gap in protection, while others blame the Omicron variant, which prevailed during the study.
Another CDC study found that two doses of Pfizer vaccine reduced the risk of Omicron infection by 31% among those aged 5 to 11 years, compared with a 59% reduction in the risk of those aged 12 to 15 years.
So far, Pfizer is the only vaccine approved for people under 18 years of age.
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