Plain language summary of Pfizer-BioNTech BNT162b2 vaccine protection against COVID-19 and its safety in participants 12-to 15-years-old

What is this summary about?This is a summary of an article about part of a clinical study for the BNT162b2 COVID-19 vaccine, also called the Pfizer-BioNTech vaccine. The article was published in the New England Journal of Medicine in May 2021. This summary describes how the vaccine worked in participants 12- to 15-years old. The part of the study described in the article is ongoing and expected to finish March 2023. This means that the final results may be different from the results included in this summary.What happened in this study?The part of the study described in this summary included participants 12- to 15-years old who had no serious health issues. The BNT162b2 vaccine had already been studied in participants 16 years of age or older. In this part of the study, the researchers wanted to find out:How effective and safe the vaccine was in participants 12- to 15-years old.What the immune response to the vaccine and the vaccine safety were like in 12- to 15-year-olds compared with 16- to 25-year-olds.How well the vaccine prevented SARS-CoV-2 infections in participants who received the vaccine compared to those who did not. This is also called efficacy of the BNT162b2 vaccine Half of the participants in this study received 2 injections of the BNT162b2 vaccine and half received 2 injections of a placebo in a muscle of the upper arm. The placebo looked like the BNT162b2 vaccine but did not have any active vaccine in it.What were the results?BNT162b2 had a favorable safety profile. The most common reactions were pain at the injection site, fatigue, and headache. None of the participants had serious reactions to the vaccine.The 12- to 15-year-old participants' immune system responses to the BNT162b2 vaccine were as good as or stronger than the 16- to 25-year-old participants' immune responses.The participants who received the BNT162b2 vaccine were less likely to get COVID-19 compared with the participants who got the placebo.