Stanford Medicine researchers have started enrolling children younger than 12 in clinical trials to evaluate their response to the Pfizer-BioNTech COVID-19 vaccine.

Stanford is serving as a site of the Phase 2-3 trial to determine whether the vaccine produces an immune response and prevents COVID-19 in children 5 through 11 years old. It is also a site of the Phase 1 trial to determine the appropriate dose of the vaccine for children 6 months to 5 years old.

The Phase 1 trial has already begun, and the Phase 2-3 trial is expected to begin mid-May. Both trials now have enough participants.

The Food and Drug Administration on May 10 authorized use of the vaccine for 12- to 15-year-olds in the United States.

“Children under 18 make up about a quarter of the U.S. population, so if we want to get the virus under control and make sure we have as many people protected by vaccines as possible, we really need to include them,” said Yvonne Maldonado, MD, professor of pediatrics and of epidemiology and population health at the Stanford University School of Medicine.

Far fewer children than adults have developed severe respiratory problems from COVID-19, but some children have become seriously ill, and a few hundred in the U.S. have died of the disease, said Maldonado, the Taube Professor in Global Health and Infectious Diseases. She added that long-term implications of contracting the SARS-CoV-2 virus in childhood are unknown. Young people are also vulnerable to a multisystem inflammatory syndrome, which typically occurs a few weeks after viral infection.

Children can spread COVID-19

“Even though the risk in children appears to be lower than in adults, this is still an important, potentially vaccine-preventable illness in kids,” Maldonado said. Children can also spread the disease to other people, meaning that vaccinating them is vital both for their own safety and to help bring the pandemic under control.