Mumps Resurgence: Understanding the Causes

Current Concerns Among Health Professionals

Mumps is experiencing a resurgence, prompting doctors to investigate the reasons behind this increase. Is the rise in cases linked to vaccine hesitancy, or are there issues with the vaccines themselves? Researchers from Harvard University are exploring these questions.

Vaccination Effectiveness and Duration of Immunity

Recent findings suggest that the MMR (measles, mumps, rubella) boosters administered at ages 13 or 14 may not be providing adequate protection. Specialists from the T.H. Chan School of Public Health indicate that mumps immunity lasts, on average, for about 27 years. This raises the possibility of implementing a second booster shot, resulting in at least three doses over an individual’s lifetime.

Since 2006, a notable rise in mumps cases has raised concerns about the effectiveness of the mumps vaccine, hindering efforts aimed at eradication.

Mumps Overview and Complications

Mumps is a highly contagious viral infection characterized by fever and swelling of the salivary glands, particularly affecting children. If contracted after puberty, it can lead to severe complications such as orchitis (testicular inflammation), meningitis, and even deafness. In Canada, the vaccination schedule requires the first dose to be administered between 12 and 15 months of age, followed by a second dose no earlier than 18 months, which must be completed before school entry.

Investigating Immunity and Vaccine Efficacy

Patterns of Infection Among Young Adults

Since 2006, there has been a significant increase in mumps infections among adults aged 18 to 29, particularly on university campuses in the United States. These outbreaks have occurred among fully immunized individuals in areas with high vaccination rates. Two primary theories have emerged to explain this trend: waning immunity and vaccine ineffectiveness.

Researchers from Harvard T.H. Chan School of Public Health reviewed six epidemiological studies focused on mumps vaccine effectiveness to uncover the cause of these outbreaks. Their findings were published in the journal Science Translational Medicine.

Research Findings on Immunity

Using mathematical models based on population data, the researchers tested the hypothesis that immunity declines over time, which would indicate waning immunity. They also considered the possibility of genetic shifts in the mumps virus, suggesting current vaccines may not be as effective as previously thought.

The analysis revealed that the resurgence in mumps cases is primarily due to waning immunity. Current vaccines provide protection for an average of 27 years. Although there has been a shift in the virus’s genetic makeup, the resurgence is largely affecting university-aged adults, indicating that the vaccination protocols remain effective.

Potential Solutions and Future Recommendations

The Role of Additional Vaccination

Vaccination remains the most effective method for preventing mumps. The results from the study support the routine administration of a third dose of the mumps vaccine to mitigate future outbreaks. A policy introduced in 1991 mandated that all U.S. military recruits receive the mumps vaccine, regardless of prior vaccination history, and has successfully prevented any cases in this group.

Following university outbreaks, students who received a third dose of the mumps vaccine showed improved immunity against the virus. However, these studies are observational and based on limited evidence. Comprehensive clinical trials are necessary to assess the safety and effectiveness of administering an additional booster shot.

The Need for Ongoing Research

Recent mumps outbreaks among young adults have hindered the goal of eradicating the disease through vaccination. Current protocols are estimated to remain effective for about 27 years, but the necessity for further doses later in life remains to be determined through additional clinical studies.

References

(1) Lewnard JA, Grad YH. Vaccine waning and mumps re-emergence in the United States. Sci Transl Med. 2018.
(2) Tesini, BL. Mumps. Merck Manual Professional Version. 2018.
(3) Canadian Immunization Guideline. Part 4 – Active Vaccines: Mumps Vaccine. 2016.