Pfizer, BioNTech opens 2nd phase of tests for COVID-19 vaccine in kids under 12

June 8 (UPI) -- Pharma company Pfizer said Tuesday it will begin testing the effectiveness of its COVID-19 vaccine in larger groups of children 11 and younger.

The company said it and partner BioNTech will conduct a study among 4,500 children at dozens of clinical sites in the United States, Poland, Spain and Finland.

"Today begins the Phase 2/3 part of our continuous study of the Pfizer-BioNTech COVID-19 vaccine in healthy children," Pfizer tweeted Tuesday.

"This is the next step allowing us to gather data to understand the safety and immunogenicity of the vaccine in this group aged 5-11 years."

The study will give three groups of children two doses three weeks apart. One group will include those 5-11, and others with children 2-5 and 6 months to 2 years old.

The first results of the study are expected in a few months.

Pzifer said children under the age of 15 account for 26% of the global population, and it believes "successfully vaccinating children will contribute to protection against COVID-19."

Tuesday's announcement came days after the European Union authorized Pfizer's COVID-19 vaccine in children ages 12-15.

Pfizer said in March that its vaccine was well tolerated and effective in children 12-15. The company began testing the vaccine in children earlier that month.