Immunity against mumps virus appears insufficient in a fraction of college-aged people who were vaccinated in childhood, research from Emory Vaccine Center and the Centers for Disease Control and Prevention indicates.
The findings highlight the need to better understand the immune response to mumps and mumps vaccines.
The results of the study are scheduled for publication in PNAS.
In the last 15 years, several mumps outbreaks have occurred among college students, sports teams and in close-knit communities across the United States.
Two possible contributing factors include waning vaccine-induced immunity and differences between the strain of mumps virus now circulating and the vaccine strain, which is part of the standard measles, mumps, and rubella (MMR) childhood vaccine.
“Overall, the MMR vaccine has been great, with a 99 percent reduction in measles, mumps and rubella disease and a significant reduction in associated complications since its introduction,” says Sri Edupuganti, MD, MPH, associate professor of medicine (infectious diseases) at Emory University School of Medicine and medical director of the Hope Clinic of Emory Vaccine Center.
“What we’re seeing now with these mumps outbreaks is a combination of two things – a few people were not making a strong immune response to begin with, and the circulating strain has drifted away from the strain that is in the vaccine.”
Emory and CDC scientists collaborated on a study that included 71 people, aged 18 to 23, in the Atlanta area – the largest study so far of mumps memory B cells in vaccinated people.
Recruitment of participants took place in 2010. Although almost all (69/71) had received two MMR doses, 80 percent of the participants received their second MMR more than ten years before enrolling in the study.
Most participants (93 percent) had antibodies against mumps, but ten percent of people in the study had no detectable mumps-specific memory B cells, which would normally be capable of producing antiviral antibodies as part of a memory response after exposure to mumps virus.
On average, the frequency of memory B cells in participants’ blood was 5 to 10 times lower for cells making antibodies against mumps, compared with cells making antibodies to measles or rubella.
In addition, antibodies from the participants did not neutralize wild-type mumps virus as efficiently as the vaccine virus.
At least six study participants may have been potentially susceptible to infection with the currently circulating wild-type mumps strain, the paper concludes. The researchers did not see a clear relationship between the timing of vaccination and low antibody or memory B cell levels.
Other research has shown that a third MMR dose resulted in increased neutralizing antibody responses to mumps in some individuals with low neutralization titers; however, the antibody levels declined toward baseline by 1 year so the effect was not long-lasting.
In 2017, the CDC’s Advisory Committee on Immunization Practices approved a third dose of MMR vaccine for groups of people who are at risk because of an ongoing mumps outbreak.
The Jeryl Lynn mumps vaccine strain in the MMR vaccine was originally cultured from a scientist’s daughter’s throat in the 1960s.
Though there is only one serotype of mumps virus, the current circulating strain (“genotype G”) is genetically distinct from the vaccine strain. How these genetic changes affect the antigenic properties of the wild-type strain is not fully understood.
Additional studies to characterize the immune response to wild-type and vaccine strains of mumps are clearly needed to determine if developing a new mumps vaccine is warranted. Developing a new mumps vaccine would take a large investment in clinical trials needed to demonstrate safety and efficacy.
Symptoms of mumps include those common to viral illnesses – fatigue, body aches, headache – but a distinctive aspect is often swelling of the salivary glands. More severe cases can lead to encephalitis or deafness. The disease is spread by direct contact, droplets, or contaminated objects. It usually takes 16 to 18 days for mumps symptoms to show up after infection starts.
MMR and MMRV Vaccine Composition and Dosage
Two vaccines containing measles, mumps, and rubella virus are licensed for use in the United States.
- M-M-R II® is a combination measles, mumps, and rubella (MMR) vaccine.
- ProQuad® is a combination measles, mumps, rubella, and varicella (MMRV) vaccine.
Both vaccines contain live, attenuated measles, mumps, and rubella virus. MMRV also contains live, attenuated varicella-zoster virus. All vaccine strains, including the Moraten strain (used in the United States) and the Edmonston- Zagreb strain are in genotype A.
The lyophilized live MMR vaccine and MMRV vaccine should be reconstituted and administered as recommended by the manufacturer1,2.
- Merck & Co. Inc. M-M-R II (Measles, mumps, and rubella virus vaccine live); 2009.
- Merck & Co. Inc. ProQuad (measles, mumps, rubella and varicella virus vaccine live lyophilized preparation for subcutaneous injection). 2011.
MMR Vaccine Effectiveness and Duration of Protection
- 1 dose of MMR vaccine is—
- 93% effective for measles (range: 39%–100%)
- 78% effective for mumps (range: 49%−92%)
- 97% effective for rubella (range: 94%–100%)
- 2 doses of MMR are—
- 97% effective for measles (range: 67%–100%)
- 88% effective for mumps (range: 31%–95%)
Duration of Protection
People who receive MMR vaccination according to the U.S. vaccination schedule are usually considered protected for life against measles and rubella. While MMR provides effective protection against mumps for most people, immunity against mumps may decrease over time and some people may no longer be protected against mumps later in life.
- Both serologic and epidemiologic evidence indicate that vaccine-induced measles immunity appears to be long-term and probably lifelong in most persons.
- While the effectiveness of two doses of MMR against mumps is high, serologic and epidemiologic studies suggest this effectiveness decreases with time. A person with a decreased immune response after time may then become infected when exposed to mumps virus through close contact with a person with mumps. A third dose of MMR can provide added short term protection for those who are likely to have close contact with a mumps patient during an outbreak.
- Studies indicate that one dose of vaccine confers long-term, probably lifelong, protection against rubella.
More information: Mohammed Ata Ur Rasheed el al., “Decreased humoral immunity to mumps in young adults immunized with MMR vaccine in childhood,” PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1905570116
Journal information: Proceedings of the National Academy of Sciences
Provided by Emory University