Moderna's COVID-19 vaccine safe and effective for young children, study finds

Results of the two-part KidCOVE study of nearly 13,000 children conducted last year at 87 sites in the United States and Canada were published in The New England Journal of Medicine.

The findings echo the results of a previous study reported in May by Creech and his colleagues that found the vaccine was safe and generated robust immune responses in children ages 6 to 11 years.

"This work is the capstone of a great deal of hard work from our team and, just as importantly, the willingness of parents and children to volunteer to find a solution to the pandemic through vaccines," said Creech, director of the Vanderbilt Vaccine Research Program and Edie Carell Johnson Professor of Pediatrics at VUMC.

Creech and Vladimir Berthaud, MD, MPH, professor, and director of the Division of Infectious Diseases at Meharry Medical College, were the paper's second and third authors. Evan Anderson, MD, from Emory University School of Medicine in Atlanta, was first author.

"Having a safe and effective (COVID-19) vaccine available for infants, toddlers and young children is critically important," the researchers reported.

COVID-19-related hospitalizations and deaths in children younger than 5 years of age during the height of the pandemic (2020-2021) in the United States surpassed annual influenza-related rates observed before the pandemic.

In addition, while infected children may be asymptomatic or have mild symptoms, they still can transmit the COVID-19 virus, SARS-CoV-2, to other people, including those at risk for serious illness and death if they become infected because of their age or underlying health conditions.

In June the U.S. Food and Drug Administration granted emergency use of the Moderna and Pfizer-BioNTech COVID-19 vaccines in children as young as 6 months of age. Moderna's mRNA-1273 vaccine had previously been authorized for use in adults 18 years and older.

"As we have seen with older age groups, we expect that the vaccines for younger children will provide protection from the most severe outcomes of COVID-19, such as hospitalization and death," FDA Commissioner Robert Califf, MD, said in a news release.

The FDA decision was based on an analysis of safety and effectiveness data reported in The New England Journal of Medicine.

Part one of the phase 2-3 clinical trial sought to compare two doses of the vaccine -- 25 and 50 micrograms -- in two groups of children, those 6 to 23 months of age and another group 2 to 5 years of age.

The 25-microgram dose elicited immune responses consistent with those observed in clinical trials involving higher doses in older children, adolescents and adults. Minor reactions included fatigue, irritability, and fever lasting two to three days.

Based on these findings, a randomized, second part of the study compared two, 25-microgram doses of the vaccine to inactive placebo in children in the two age groups. The doses were administered 28 days apart.

Vaccine efficacy in the study, which was conducted when the more contagious omicron variant was widely circulating, was lower than that reported in previous clinical trials conducted when other variants were predominant. However, vaccine efficacy matched that observed in adults studied during the omicron wave.

The 25-milligram dose also was sufficient to elicit robust antibody levels against a broad range of variants in young children, and it was associated with a lower rate of COVID-19 infections compared to placebo.

Thus, the researchers concluded, "primary vaccination offers protection against (COVID-19-related) hospitalization and death."

The KidCOVE (Coronavirus Efficacy) trial was supported by the Office of the Assistant U.S. Secretary for Preparedness and Response, the Biomedical Advanced Research and Development Authority (BARDA), and by National Institutes of Health grants AI148576, AI148452, AI148689, AI148450, AI148372, and AI148575.