3 doses of Pfizer vaccine are effective, says Pfizer

Three doses of Pfizer-BioNTech’s Covid-19 vaccine for younger children were 80% effective against the omicron variant of the coronavirus, according to initial data released by the company on Monday.

The long-awaited results bring the vaccine one step closer to a reality for parents of children aged 6 months to 4 years – the only group that remains ineligible for vaccination.

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Results from the company’s Phase 2/3 clinical trial also found the vaccine – which uses a dose one-tenth the level used for adults – generated a strong immune response and was safe.

The results suggest that the low-dose vaccine “provides young children with a high level of protection against recent strains of Covid-19,” Dr. Uğur Şahin, CEO and co-founder of BioNTech, said in the statement. “We are preparing the relevant documents and expect to complete the FDA submission process this week.”

The 80% efficiency figure may change as the company collects more data. It is based on 10 symptomatic Covid cases that occurred seven days after the third dose of the vaccine as of April 29. A formal analysis will be performed once there are at least 21 positive cases in the clinical trial. Safety and immune response data are finalized, the company said.

The first two doses of the vaccine are given three weeks apart, followed by a third dose at least two months later.

The results were announced in a press release and the full data was not made available to outside experts for review.

Dr Isaac Bogoch, an infectious disease specialist at the University of Toronto, said while the results are “useful”, more data on the vaccine in young children is still needed.

“In the age of the omicron, it doesn’t appear that vaccine protection against infection is durable,” he said. “It would be useful to feed studies to see the protective benefit of two versus three doses of vaccine against severe infection, which is less common in this age cohort but can still occur.”

Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center, said Pfizer’s trial data may be too small to detect myocarditis, although he doesn’t expect inflammatory heart disease be a problem for this age group. The Covid mRNA vaccines, from Pfizer and Moderna, have been associated with a small but increased risk of side effects in older adolescents and young adults.

Covid cases are on the rise again in the United States, including among children. The American Academy of Pediatrics reported 93,000 new cases in children in the week ending May 12, up 76% from the previous two weeks. Cases have increased in children over the past five weeks, the academy said.

The rollout of a vaccine for the youngest age group – originally planned for the end of 2021 – has had a series of hiccups, leaving parents and pediatricians frustrated that the smallest children remain ineligible for vaccination.

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In December, Pfizer said two doses of the vaccine did not generate a strong enough immune response in children 2 to 4 years old and as a result it would collect data on a three-dose regimen.

Even so, the company planned to submit data on both doses to the Food and Drug Administration in February. The idea was that the agency could at least begin the review process and potentially get children started with the first two doses of the vaccine, knowing that a third would be added later.

An advisory committee meeting to review the two-dose regimen, however, was postponed due to concerns that the data was insufficient.

Moderna submitted its vaccine application for children under 6 at the end of April.

Dr. Doran Fink, deputy director of the FDA’s vaccines division, said in a public meeting Thursday that the agency was working to get Moderna’s request to its advisory committee as “quickly as possible.”

The FDA plans to convene its Vaccine Advisory Committee on June 15 to discuss Moderna and Pfizer vaccines for young children.

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