The mRNA-1273 Vaccine at 25-μg Dosage May Protect Infants, Young Children Against Omicron

The Moderna mRNA-1273 vaccine was found to be effective for more than 50% of children aged 6 to 23 months.

For children aged 6 months to 5 years, researchers observed that 2 primary doses of Moderna’s messenger RNA vaccines (mRNA)-1273 vaccine can protect against hospitalization and death from COVID-19, according to authors of a study published in the New England Journal of Medicine. The authors explained further that young study participants who tested positive for COVID-19 were found to have the Omicron BA.1 and BA.1.1 variants, with the study researchers suggesting two 25-μg doses of the mRNA-1273 vaccine to protect against a wide range of other variants.

“Two 25-μg doses of the mRNA-1273 vaccine were found to be safe in children 6 months to 5 years of age and elicited immune responses that were noninferior to those in young adults,” wrote the study authors.

From October 2020 to September 2021, the data show that there were more hospitalizations and deaths among children aged 5 years and younger from SARS-CoV-2 than pre-pandemic influenza-related rates. However, although Moderna’s COVID-19 mRNA vaccine has been proven safe and effective against the spread of COVID-19 in adults, adolescents, and children aged 6 years and older, the mRNA vaccine from Moderna is not yet authorized for children younger than age 6, while children who are at least 6 months of age can receive it in an emergency.

Since, it has been shown that 2 doses of Moderna’s mRNA vaccine (mRNA-1273) can protect against hospitalization and death, the KidCOVE phase 2 and 3 trial was conducted to evaluate the safety, reactogenicity, immunogenicity, and efficacy of mRNA-1273 vaccine in children aged 6 months to 5 years. During the study, the primary endpoints included safety, vaccine reactogenicity, and a noninferior immune response to young adults in a related phase 3 trial. Secondary endpoints were defined as incidences of COVID-19 and SARS-CoV-2 infection, in both the mRNA-1273 and placebo groups.

In part 1 of the trial, researchers evaluated safety and immunogenicity of the 25-μg mRNA-1273 dose. In part 2, the children aged 6 months to 5 years were randomly assigned to receive two 25-μg doses of mRNA-1273 or the placebo, with a median follow-up of about 70 days, depending on age.

By day 57, the mean concentration of neutralizing antibodies was only 300 less than young adults who had received two 100-μg injections, “[which] met the noninferiority criteria for immune responses for both age cohorts,” study authors wrote in the report.

The 25-μg mRNA-1273 dose triggered mild-to-moderate and transient reactogenicity, including fever, which affected 22 to 23% of patients. At analysis-cutoff, there was no myocarditis pericarditis—nor incidences of death—and adverse events were mostly low-grade.

The researchers noted that the study also has some limitations. Primarily, researchers enrolled heathy children with stable medical conditions to participate. Additionally, the researchers did not evaluate the efficacy of the vaccine in the long-term.

“Active and passive safety surveillance will continue during the post authorization period in large global safety networks to detect any new safety signals,” the study authors wrote. “The longer-term effectiveness and durability of mRNA-1273 will also continue to be assessed in clinical trials and through its post authorization use.”

Reference

Anderson EJ, Creech CB, Berthaud V, et al. Evaluation of mRNA-1273 Vaccine in Children 6 Months to 5 Years of Age. October 19, 2022, NEJM. doi:10.1056/NEJMoa2209367