Pfizer or Moderna for Young Children? Some Differences In Studies, Timing

Covid vaccines for children 6 months to 5 years have been approved by the FDA as of June 18. Additionally, on June 19, CDC director Dr. Rochelle Walensky recommended the vaccines for this age group after meeting with with the Advisory Committee on Immunization Practices (ACIP). Both vaccines underwent rigorous review, and benefits to children were determined to outweigh vaccine risks.

Both Pfizer and Moderna are approved for children as young as 6 months, but there are some key differences. Moderna is approved for 6 months to 5 years, while Pfizer is approved for 6 months to 4 years. Studies are underway for both vaccines  to determine if boosters are needed. Both vaccines have been shown to provide protection against severe disease, hospitalization and death, as well as similar immune responses to adults receiving the vaccines.

Moderna data is derived from two randomized, blinded, placebo-controlled trials that enrolled 11,700 children; 6,700 were under the age of 6. The trial still ongoing in both the US and Canada and was conducted during the Omicron surge. 

The Moderna vaccine series requires two doses a month apart, although an additional vaccination a month after the second is approved for children who are immunocompromised. The vaccine was about 50% effective at preventing a Covid infection in children 6 to 23 months and about 37% effective at preventing a Covid infection in children 2 to 5 years of age. Most common side effects are injection site soreness, pain and redness; fever; and underarm pain/swelling of underarm lymph nodes.

Pfizer data is derived from an ongoing randomized, blinded, placebo-controlled study in the US and internationally that enrolled 4,500 children, with 1,678 5 years of age and younger. It’s important to note that, unlike with Moderna, this study was conducted prior to the Omicron surge. That’s relevant because efficacy data is derived from variants prior to Omicron, so this study does not reflect how the Pfizer vaccine will respond specifically to Omicron.

The immune response in children receiving the Pfizer vaccine was comparable to those in older age groups, and 80% of symptomatic infections were prevented after a third dose of the vaccine.  The Pfizer vaccination series includes three doses, with the second vaccination spaced three weeks after the first and the third injection at least eight weeks from the second. Most commonly reported side effects post injection were irritability, reduced appetite, fever and pain and swelling at the injection site.

Although there were no cases of myocarditis or pericarditis in either study, there is continuing analysis of the increased risk of inflammation of the heart muscle and/or of the outer lining of the heart following vaccination with either Pfizer or Moderna. The highest risk of occurrence for these conditions has been in males age 18 to 24. International data suggests rapid resolution with conservative management, with no change in quality of life reported at 90 days after reporting the diagnosis.

Vaccinations can be found at pediatrician’s offices, retail clinics such as Minute Clinics that are authorized to provide vaccinations for those 18 months and up as well as pharmacies that provide vaccines for those 3 years and up. Find a vaccine here.

As of February, about 75% of children have already had Covid, but the vaccine is still advised because natural immunity wanes after infection; additionally, previous studies have shown that a mix of natural and vaccine-mediated immunity may be the most beneficial in preventing symptomatic disease.