Coronavirus: Pfizer expands vaccine trial for children under 12

Pfizer officials on Tuesday announced that the company is expanding the number of children included in its vaccine tests as the company works toward submitting data to regulators for an emergency use authorization in the fall.

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In March, company officials said they were launching tests of the two-dose vaccine developed by Pfizer and by German biotechnology firm BioNTech with 144 participants and plans to widen that range to 4,500. The trial will include children between the ages of 6 months and 11 years in the U.S., Finland, Poland and Spain.

>> Related: Coronavirus: Pfizer, BioNTech begin testing COVID-19 vaccine in children under 12

The company chose a lower dose of the vaccine to test in children than used for adult vaccinations, Reuters reported. The first two participants in the trial, a pair of 9-year-old twin girls, received their first shots of the Pfizer/BioNTech vaccine at Duke University in North Carolina on March 28, according to The New York Times.

Pfizer officials said they aim to ask the Food and Drug Administration for an emergency use authorization to use its drug to vaccinate children from 5 to 11 years in September or October. Company officials said they expect to apply for an emergency use authorization to vaccinate children between 6 months and 5 years old “soon after.”

>> Related: Moderna begins testing COVID-19 vaccine for children

Regulators authorized emergency use of the the Pfizer/BioNTech vaccine for adults in December, making it the first vaccine against COVID-19 available in the U.S. In a clinical trial, the companies’ drug had an efficacy rate of 95%, according to the U.S. Food and Drug Administration.

As of Monday afternoon, the most recent date for which data was available, 302.8 million COVID-19 vaccine doses have been administered nationwide. According to the Centers for Disease Control and Prevention, 139.7 million Americans have been fully vaccinated so far, amounting to about 42% of the population. The numbers include about 25,000 people under the age of 12 who have so far been fully vaccinated.

>> Related: Coronavirus: Half of U.S. adults fully vaccinated, CDC data shows

More than 33.3 million people across the U.S. have tested positive for COVID-19 since the start of the pandemic, according to a tally from Johns Hopkins University. The viral infection has claimed over 598,000 lives nationwide.

Globally, nearly 174 million people have tested positive for COVID-19, resulting in over 3.7 million deaths, according to Johns Hopkins.