Is Priorix (Measles, Mumps, and Rubella vaccine) more effective than MMRII (Measles, Mumps, and Rubella vaccine)?

Priorix vs. MMRII: Effectiveness Comparison

Priorix and MMRII vaccines are considered fully interchangeable with similar effectiveness for preventing measles, mumps, and rubella, with no significant differences in immunogenicity or clinical outcomes. 1

Vaccine Effectiveness

Both Priorix and MMRII demonstrate excellent effectiveness in preventing measles, mumps, and rubella:

• Measles protection: 95% effectiveness after one dose and 96% after two doses (moderate certainty evidence) 2
• Mumps protection: 72% effectiveness after one dose and 86% after two doses with Jeryl Lynn strain (contained in both vaccines) 2
• Rubella protection: 89% effectiveness 2

Immunogenicity Comparison

Multiple studies have directly compared Priorix and MMRII:

• Four studies conducted with Priorix at U.S. potency found no significant difference in anti-measles, anti-mumps, or anti-rubella geometric mean concentrations (GMCs) after the first dose between Priorix and MMRII recipients 1
• Studies showed no significant difference in antibody levels for any antigen after a second dose between Priorix and MMRII recipients 1
• Long-term immunity studies found no difference between vaccines in antibody persistence 2 years after vaccination 1

Safety Profile Differences

While both vaccines have excellent safety profiles, there are some differences:

• Priorix causes significantly less pain at the injection site compared to MMRII, as demonstrated in clinical trials 3
• In most clinical studies comparing Priorix with MMRII as a primary vaccination in infants, Priorix was associated with significantly fewer local adverse events (pain, swelling, and redness) 4
• Both vaccines have similar rates of fever, rash, and parotid gland swelling 4

Interchangeability

The Advisory Committee on Immunization Practices (ACIP) has explicitly stated:

• Priorix and MMRII are fully interchangeable for all indications 1
• Either vaccine may be administered in any situation where an MMR virus-containing vaccine is indicated 1
• Studies have shown that Priorix is safe and immunogenic when administered as a second dose after MMRII 1

Practical Considerations

• Both vaccines follow the same administration schedule: first dose at 12-15 months and second dose at 4-6 years 1, 2
• Both are administered as subcutaneous injections 1
• Priorix is supplied as a single-dose vial of lyophilized antigen to be reconstituted with accompanying prefilled syringe of sterile water diluent 1
• Having two interchangeable vaccines from different manufacturers helps safeguard the U.S. vaccine supply 1

Clinical Decision-Making

When choosing between Priorix and MMRII:

• Primary consideration: Both vaccines are equally effective at preventing measles, mumps, and rubella 1, 2
• Secondary consideration: Priorix may cause less injection site pain, which could be beneficial particularly in younger children 3
• Practical consideration: Use whichever vaccine is available, as they are fully interchangeable 1

In summary, while both vaccines provide equivalent protection against measles, mumps, and rubella, Priorix may offer a slight advantage in terms of reduced injection site pain, making it a potentially preferable option when both vaccines are available.