Is it contraindicated to administer the Measles, Mumps, and Rubella (MMR) vaccine and the Varicella (chickenpox) vaccine on the same day for a 1-year-old?

MMR and Varicella Vaccines Can and Should Be Given on the Same Day to a 1-Year-Old

It is not contraindicated to administer MMR and varicella vaccines on the same day for a 1-year-old—in fact, simultaneous administration is explicitly recommended by ACIP to ensure timely protection and improve vaccination coverage. 1

Evidence Supporting Same-Day Administration

Immunogenicity and Effectiveness

• MMR and varicella vaccines administered on the same day produce identical immune responses compared to vaccines given one month apart. 1
• Seroconversion rates for all four antigens (measles, mumps, rubella, varicella) are equivalent whether vaccines are given simultaneously or separately, with rates exceeding 96-99% for all components. 2
• Long-term protection remains robust, with varicella antibody persistence rates >98-100% during 6 years of follow-up regardless of whether vaccines were given together or apart. 2

Safety Profile

• Adverse reaction rates (fever, injection site reactions, rashes) are similar whether MMR and varicella are administered simultaneously or separately. 2
• No evidence exists of immunologic interference between these vaccines when given on the same day. 1

Critical Decision Point: MMRV vs. Separate MMR + Varicella

For a 1-year-old receiving the first dose, you should administer separate MMR and varicella vaccines rather than the combination MMRV vaccine, unless parents specifically request MMRV after informed discussion. 1, 3

Why Separate Vaccines Are Preferred for First Dose (Ages 12-47 Months)

• MMRV vaccine doubles the risk of febrile seizures compared to separate MMR + varicella vaccines, causing approximately one additional febrile seizure per 2,300-2,600 doses administered. 1, 3
• This increased risk occurs specifically 5-12 days after the first dose in children aged 12-23 months. 1
• The 47-month age cutoff was selected because 97% of all febrile seizures occur in children ≤47 months of age. 1, 3

When MMRV Is Acceptable

• For the second dose at any age, or for the first dose in children ≥48 months, MMRV is generally preferred over separate injections. 1, 3
• At these ages/doses, the increased febrile seizure risk is not observed. 4

Specific Precautions for MMRV (Not for Separate MMR + Varicella)

Screen for personal or family history (sibling or parent) of seizures of any etiology before considering MMRV. 1, 3

• If positive history exists, use separate MMR and varicella vaccines because the risks of MMRV outweigh benefits in this population. 1, 3
• This precaution applies specifically to MMRV, not to separate vaccine administration. 1

Clinical Implementation Algorithm

For a 1-year-old due for first dose:

1. Confirm no contraindications to live vaccines (immunodeficiency, pregnancy, recent antibody-containing blood products, severe immunosuppression). 1

2. Screen for seizure history (personal or family). 1, 3

3. Discuss options with parents:

   • Explain that separate MMR + varicella = 2 injections but lower febrile seizure risk
   • Explain that MMRV = 1 injection but approximately 1 extra febrile seizure per 2,300-2,600 doses 1, 3

4. Unless parents specifically prefer MMRV, administer separate MMR and varicella vaccines on the same day. 1, 3

Common Pitfalls to Avoid

• Do not delay varicella vaccine to a separate visit. Approximately one-third of measles cases during outbreaks occurred in vaccine-eligible children who could have been protected if MMR had been given at the same visit as another vaccine. 1
• Do not confuse the febrile seizure risk with long-term neurological harm. Febrile seizures do not cause epilepsy, neurological damage, or neurodevelopmental delays. 3
• Do not use the MMRV precautions for separate vaccine administration. The increased febrile seizure risk is specific to MMRV, not to MMR + varicella given separately. 1