MMRV Vaccine for Second Dose at 37 Months
For a 3-year-and-1-month-old child receiving their second dose of MMR, MMRV vaccine is generally preferred over separate MMR and varicella vaccines. 1, 2, 3
Age-Based Recommendation
At 37 months of age (≥48 months threshold does not apply here, but the child is receiving a second dose), MMRV is the preferred option because the increased febrile seizure risk only applies to children aged 12-23 months receiving their first dose of measles-containing vaccine. 1, 2, 3
Postlicensure studies definitively show that children aged 4-6 years receiving the second dose of MMRV have no increased risk for febrile seizures compared to those receiving separate MMR and varicella vaccines. 1, 4
The ACIP specifically states that for the second dose at any age (15 months–12 years), use of MMRV vaccine is generally preferred over separate injections. 1, 2
Key Safety Considerations
Febrile Seizure Risk Profile
The approximately 2-fold increased febrile seizure risk (1 additional seizure per 2,300-2,600 vaccinated children) occurs only during days 5-12 after the first dose in children aged 12-23 months. 1, 5
For second doses, the febrile seizure rate after MMRV is not elevated compared to MMR+V, with adjusted odds ratio of 1.04 (95% CI 0.82-1.32). 4
Clinical trial data from over 2,700 children receiving a second dose of MMRV showed a febrile seizure incidence of only 0.07% (2/2,695), compared to 0.26% after first dose. 6
Contraindications and Precautions
Personal or family history (sibling or parent) of seizures is a precaution for MMRV. In such cases, administer separate MMR and varicella vaccines instead. 1, 2, 3
This precaution applies regardless of whether it is the first or second dose. 1
Practical Advantages
MMRV reduces the number of injections from two to one, improving vaccine acceptance and compliance. 1
The combination vaccine provides equivalent immunogenicity and protection compared to separate administration. 3, 7
Using MMRV for the second dose may increase varicella vaccine coverage, particularly in states without school-entry requirements for a second varicella dose. 1
Expected Adverse Events
Injection-site reactions (redness, pain/tenderness) may occur, with redness being slightly more common after the second dose. 6
Fever and rash may occur 7-12 days after vaccination but are less frequent after the second dose compared to the first dose. 8, 6
Overall adverse event rates are lower after the second dose (57.7%) compared to the first dose (70.5%). 6