The Pfizer / BioNTech vaccine against coronavirus is much less effective in preventing infection in children aged five to 11 years than it is in adolescents and adults, according to a new major US scientific study.
This vaccine is so far the only one approved by the US Food and Drug Administration (FDA) for children aged 5-11. According to the latest data from the New York Times, the vaccine protects children of this age from severe Covid-19, but provides almost no protection against the possibility of infection, even just one month after they have been fully vaccinated. .
The new study, conducted amid the spread of the Omicron variant (December 2021 and January 2022), analyzed data from 852,384 fully vaccinated children aged 12-17 years and 365,502 aged 5-11 years. The researchers did the relevant pre-publication on medRxiv.
The efficacy against the risk of hospitalization decreased from 85% to 73% in adolescents, while in young children from 100% to 48%. Efficacy against infection risk decreased in older children from 66% to 51% and in young children from 68% to just 12%. A large difference was observed between the age of 12 years (efficiency 67%) compared to that at the age of 11 years (only 11%).
The large reduction in effectiveness is probably due, according to researchers and the US health authorities, to the fact that young children receive only one third of the dose of older children and adults. The results of a clinical trial recently showed that the vaccine was also less effective in two- to four-year-olds taking an even lower dose.
“The difference between the two age groups is striking,” said Dr. Florian Kramer, a leading immunologist at Mount Sinai Medical School in New York. This difference is probably explained because 12-year-olds received a dose of 30 micrograms of the vaccine, while 11-year-olds received only 10 micrograms.
Experts in the US have expressed concern that the above will make some parents even more reluctant to vaccinate their children against coronavirus. “It’s disappointing, but not entirely unexpected, given that this is a vaccine developed in response to a previous variant. However, it seems very disappointing to see such a rapid decline (in effectiveness) against Omicron,” said lead researcher Eli Rosenberg. of the New York State Department of Health.
However, experts continue to recommend the vaccine for children, as it continues to protect against the serious disease Covid-19. “We need to focus clearly on the donut itself, not its hole,” said Dr. Kathryn Edwards, a pediatric vaccine specialist at Vanderbilt University in Tennessee.
The findings, according to Dr. Rosenberg, raise questions about what is the right dose for young children, how many doses should be given and when. So far in the US only one in four children aged 5-11 have taken two doses of the Covid-19 vaccine (the CDC has not yet recommended a third booster for this age group), and the FDA has not yet approved the vaccine for children under five years. Pfizer and BioNTech continue to try a third dose in children 5-11 years old and under five years old, with results expected within a few weeks.
Another recent British study showed that the effectiveness of the vaccine against symptomatic infection in adolescents 12-17 years falls after only two months to only 23%.
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