Pfizer vaccine significantly less effective in children ages five to 11, study shows

Strikingly higher rates of decline in effectiveness for younger children suggest the lower dose they receive may be the reason

The Pfizer/BioNTech Covid-19 vaccine is less effective in children aged five to 11 than in adolescents and adults, according to new data from New York state health officials.

The new research was announced shortly after federal authorities relaxed masking guidance and a day after Eric Adams, the mayor of New York, said he would probably follow Governor Kathy Hochul in ending a mask mandate in city schools.

The study was carried out during the Omicron variant surge but was made public at a time of rapidly dropping cases and hospitalizations in New York and elsewhere.

In the study released on Monday, not yet peer-reviewed, six New York state public health scientists analyzed cases and hospitalization rates from 13 December 2021 to 30 January 2022 among 852,384 fully vaccinated children aged 12 to 17 and 365,502 fully vaccinated children aged five to 11.

Results revealed that vaccine effectiveness against hospitalization during the Omicron variant surge declined from 85% to 73% for children aged 12 to 17.

Among children aged five to 11, effectiveness fell even more significantly, from 100% to 48%.

Vaccine effectiveness against testing positive declined from 66% to 51% among children aged 12 to 17. In the younger group, effectiveness dropped from 68% to 12%.

In the last week of January, vaccine effectiveness against hospitalization among 12-year-olds was 67% – but just 11% for 11-year-olds.

“The difference between the two age groups is striking,” Florian Krammer, an immunologist at Mount Sinai’s Icahn School of Medicine, told the New York Times.

He noted that 12-year-olds were administered 30mg of the vaccine, the same dose given to adults. But 11-year-olds were given only 10mg.

“This is super interesting because it would almost suggest that it’s the dose that makes the difference … the question is how to fix that,” Krammer said.

Eli Rosenberg, the New York state deputy director for science, told the New York Times that although it was disappointing to see the decline in vaccine effectiveness, it should be acknowledged that the Pfizer/BioNTech shot was developed in response to an earlier virus variant.

“It looks very distressing to see this rapid decline but it’s again all against Omicron,” he said.

News of the research came shortly after the Centers for Disease Control and Prevention (CDC) outlined new mask guidelines for more than 70% of the US population.

The new system changes the CDC risk map and puts more than 70% of the population in counties where coronavirus is posing a low or medium threat to hospitals. Those people can stop wearing masks in many settings, the agency said.

Nevertheless, the CDC is still advising that people including schoolchildren wear masks where the risk of Covid-19 is high. That is the situation of approximately 37% of US counties, where about 28% of Americans liv

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