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

American drug manufacturer Pfizer and German biotechnology company BioNTech have begun to test their COVID-19 vaccine in children under 12, company officials announced Thursday, according to multiple reports.

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Officials expect to enroll 144 participants as young as 6 months old into the first part of the trial before expanding the volunteer pool to 4,500 more children in the U.S. and Europe, Bloomberg reported. In the second phase of the trial, two-thirds of children will get the vaccine, while the rest will get a placebo, according to the news site.

Pfizer officials hope the trial will allow the company to extend vaccinations to children between 6 months and 11 years old by early 2022, Reuters reported.

>> Related: Coronavirus: When can teenagers, younger children be vaccinated?

The first two participants in the trial, a pair of 9-year-old twin girls, received their first shot of the two-dose Pfizer/BioNTech vaccine at Duke University in North Carolina on Wednesday, according to The New York Times.

The trial begins after officials with Massachusetts-based biotechnology company Moderna announced last week that they had started to test a COVID-19 vaccine for children between the ages of 6 months and 11 years.

>> 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 Wednesday morning, the most recent date for which data was available, 130.4 million COVID-19 vaccine shots have been administered nationwide. According to the Centers for Disease Control and Prevention, 46.3 million Americans have been fully vaccinated so far, amounting to about 14% of the population.

More than 30 million people across America 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 545,000 lives nationwide.

Globally, nearly 125 million people have tested positive for COVID-19, resulting in over 2.7 million deaths, according to Johns Hopkins.