Data indicate that the levels of antibody against the mumps virus decrease after childhood. “Waning of immunity is a major cause in the re-emergence of mumps among vaccinated young adults,” explains Patricia Kaaijk, PhD, “A third dose of the measles-mumps-rubella (MMR) vaccine that increases antibody levels may protect young adults who are at risk for mumps.” Dr. Kaaijk and colleagues conducted a study, published in The Journal of Infectious Disease, to determine the safety and antibody responses to a third dose of the MMR vaccine (MMR-3) in young adults aged 18 to 25.

In the prospective study, participants with mean age of 22.4 years who received MMR-3 underwent blood samples just before vaccination, as well as 4 weeks and 1 year after in order to gauge antibody levels to the mumps virus. Antibody levels were log transformed to achieve normal distributions. Differences in antibody concentrations were analyzed with the NcNemar test.

Safe & Effective

Participants were asked to track their temperature and record pain, redness, or swelling at the injection site, as well as rash, neck gland swelling, and arthralgia or myalgia for the first 2 weeks after vaccination. No serious adverse reactions were reported during the study. However, 17% of participants reported one or more mild adverse events at the injection site (12% local pain, 7% redness, and 5% swelling). Although 33% of participants experienced one or more systemic adverse events (16% swelling neck glands, 18% arthralgia or myalgia, 4% fever, and 3% rash), all adverse events were mild and resolved by 4 weeks follow-up.

Blood samples indicated that before receiving MMR-3, participants had an average immunoglobulin G (IgG) geometric mean concentration (GMC) of 186 RU/mL, a neutralizing antibody dilution of serum that resulted in 50% plaque reduction (ND50) titer against the vaccine strain of 88.8, and a ND50 titer against previous outbreak strain of 65.3. Blood samples 4 weeks after injection indicated that antibody levels were increased by 1.65-, 1.34-, and 1.35-fold to an IgG concentration of 306 RU/mL, vaccine strain ND50 titer of 119, and the outbreak strain ND50 titer of 88.4, respectively. Data suggest that more than 86% of participants were protected against mumps, which was confirmed with all three serological assays. The same level of protection persisted at 1-year follow-up (Table). “The third MMR vaccination increased antibody levels protecting recipients for longer than had previously been hypothesized,” says Dr. Kaaijk. “While the antibody levels declined 1 year after vaccination, the antibody levels were still significantly higher than before vaccination. The data support that a third MMR dose could help safely control a mumps outbreak.”

Increasing Antibody Protection

Looking to future implementation, Dr. Kaaijk is encouraged. “Physicians are recommended to follow the childhood vaccination program for two MMR vaccinations as advised by national health authorities,” explains Dr. Kaaijk. “Our data strengthen the recent recommendation of the Advisory Committee on Immunization Practices (ACIP) to offer a third dose of a mumps virus-containing vaccine to persons who are identified to be at risk of mumps during an outbreak to prevent mumps virus infection and related complications. In addition, we now provide evidence that MMR-3 vaccination boost the waning immunity and thereby prevent mumps virus infection and related complications for at least 1 year.”

Dr. Kaaijk notes that continued research is still needed in this area. “Moving forward, our team will investigate whether the elevated antibody levels still persist 3 years after the third MMR dose, through collection of follow-up blood samples,” she says. “In addition to antibodies, other immune factors can play a role in the defense against mumps. We intend to investigate the effects of a third dose of the MMR vaccine on these other immune factors (eg, cellular immunity) as well.”