Is it acceptable to administer a third Measles, Mumps, and Rubella (MMR) vaccine to a 19-year-old patient who received two doses of the MMR vaccine more than 10 years ago during an outbreak?

From the Guidelines

It is generally safe and appropriate to administer another MMR vaccine to a 19-year-old patient who completed their two-dose series more than 10 years ago during an outbreak situation. The standard MMR vaccine schedule consists of two doses, typically given at 12-15 months and 4-6 years of age, which usually provides long-lasting immunity. However, during outbreaks, public health authorities may recommend an additional dose to boost immunity, especially in high-risk settings like college campuses or communities experiencing active transmission.

Key Considerations

• The additional dose is administered as a standard 0.5 mL subcutaneous injection, identical to previous doses.
• This approach is considered safe, with side effects typically limited to mild reactions such as soreness at the injection site, low-grade fever, or mild rash.
• The scientific rationale for an additional dose during outbreaks is that while most individuals maintain immunity after two doses, some may experience waning antibody levels over time, and the extra dose provides enhanced protection by boosting the immune response in a high-risk situation, as supported by studies such as 1.

Evidence-Based Decision

The decision to administer an additional MMR dose is based on the understanding that two doses of measles vaccine are necessary to develop adequate population immunity to prevent measles outbreaks among school-aged and older persons, as indicated in 1. Furthermore, mumps can occur in highly vaccinated populations, and in these outbreaks, substantial numbers of cases have occurred among persons who had previously received a single dose of mumps-containing vaccine, highlighting the potential benefit of an additional dose in preventing such cases, as noted in 1.

Clinical Application

In clinical practice, the administration of an additional MMR dose during an outbreak situation should be guided by public health recommendations and the individual patient's risk factors, including their vaccination history, age, and potential exposure to the virus. The patient's medical history and any contraindications to the vaccine should also be considered, as outlined in guidelines such as 1.

From the Research

MMR Vaccine Administration in Outbreaks

• The administration of a third dose of MMR vaccine in an outbreak situation is supported by studies such as 2, which found that a third dose of MMR vaccine can boost rubella-specific humoral immunity in women of childbearing age.
• Another study 3 found that long-term neutralizing antibody levels against measles and rubella viruses remain high in adults up to 11 years after receipt of a third MMR dose, suggesting that a third dose can provide long-term protection.

Immune Response to MMR Vaccine

• A study 4 found that a large proportion of pre-school children had measles and mumps IgG antibody levels below the putative level of protection 2-4 years after receiving a first dose of MMR vaccine, highlighting the importance of a second dose.
• The same study 4 found that after a second dose of MMR, the proportion of children with negative or equivocal levels to one or more antigens dropped to <4%, indicating a strong immune response to the second dose.

Considerations for 19-Year-Old Patient

• Given that the patient had both MMR shots more than 10 years ago, it is possible that their immune response may have waned over time, as suggested by study 3, which found that measles antibody levels can decline over time.
• However, study 2 found that a third dose of MMR vaccine can boost antibody levels, even in individuals who have previously received two doses, suggesting that a third dose may be beneficial in an outbreak situation.