Early MMR Vaccination is not linked to Reduction in Hospitalizations for Non-Targeted Infections in Infants: BMJ study

Researchers allocated Infants in 1:1 to intramuscular injection with standard titre MMR vaccine (M-M-R VaxPro) or placebo (solvent only).

In Denmark, the first three doses of DTaP-IPV-Hib+PCV are scheduled at 3, 5, and 12 months of age—that is, the first two doses were administered before randomization and the third dose at the end of follow-up. To account for a possible effect of diphtheria, tetanus, and pertussis as the latest administered vaccine, we performed an analysis where the infants were censored at the date of immunization with DTaP-IPV-Hib+PCV after randomization.

The study results are:

• Six thousand five hundred thirty-six infants were included.
• Three thousand two hundred sixty-four infants randomized to the MMR vaccine experienced 786 hospitalizations for infection before age 12 months compared with 762 for the 3272 infants randomized to placebo.
• There was no difference in the rate of hospitalizations for infection between the MMR vaccine and placebo groups.
• For infants randomized to the MMR vaccine compared with those randomized to placebo, the hazard ratio of hospitalizations for infection with a duration of at least 12 hours and prescriptions of antibiotics was 1.25 and 1.04, respectively.
• The estimate did not change when censoring at the date infants received DTaP-IPV-Hib+PCV after randomization (1.02, 0.90 to 1.16).

The primary outcome of our study was hospitalizations for infection, they said.

We found that live attenuated MMR vaccine administered to infants at 5-7 months of age did not decrease the rate of hospitalizations for non-targeted infection before age 12 months, they concluded.

The study’s strengths were a randomized controlled design, complete follow-up, and less risk of bias.

Further reading:

https://www.bmj.com/content/381/bmj-2022-072724