Over the past few years, there has been a resurgence in mumps outbreaks across the USA and other parts of the world. Although these outbreaks did not spread widely as they did before the advent of mumps vaccines, it still required some scientific research into why this happened. According to just published peer-reviewed research, much of the mumps outbreaks may result from waning mumps vaccine effectiveness.
Because I am concerned that this new article will be misinterpreted by some parts of the discussion, I’m glaring at the anti-vaccine religion, it is important that we take a very careful look at this well-done study examining what could be the root cause of some outbreaks – waning immunity to the mumps vaccine.
Many people think mumps is a minor disease, something you can overcome with a little bed rest and homeopathic potions. This belief results from a lack of personal history with the disease by parents of today. It has been over 50 years since major mumps epidemics swept through children.
Mumps is caused by the mumps virus. According to the CDC, the initial symptoms of the disease include fever, muscle pain, headache, and feeling tired. This is similar to many other infectious diseases, including the flu. However, these early symptoms are usually followed by painful swelling of one or both parotid salivary glands.
Mumps symptoms generally occur 16-18 days after initial exposure, and the symptoms resolve after 7-10 days. Symptoms in adults are often more severe than in children (pdf).
The CDC reports that there can be severe complications from the mumps. These include:
- Meningitis (swelling of the tissue covering the brain and spinal cord), which occurs in about 15% of cases.
- Pancreatitis, which occurs in about 4% of cases.
- Deafness (temporary or permanent)
- Encephalitis (swelling of the brain)
- Orchitis (swelling of the testicles) in males who have reached puberty, which can lead to permanent infertility
- Oophoritis (swelling of the ovaries) and/or mastitis (swelling of the breasts) in females who have reached puberty
- In rare cases, mumps can cause death.
Mumps is highly contagious, spreading quickly in close quarters. The virus is spread through respiratory droplets in the air. Children, teens, and adults who are frequently in these closed spaces, like classrooms, dormitories, and offices can be susceptible to an outbreak.
Mumps can be prevented by the mumps vaccine, which is a part of the MMR vaccine (against measles, mumps, and rubella). The Advisory Committee on Immunization Practices (ACIP) and Centers for Disease Control and Prevention (CDC) recommend two doses of the MMR vaccine for children – the first dose is given at age 12 through 15 months, and the second dose is given at age 4 through 6 years, prior to starting school.
Let’s take a look at the article
This new article, published in Science Translational Medicine by Joseph A Lewnard and Yonatan H Grad, of the Harvard T.H. Chan School of Public Health, examined the resurgence of mumps outbreaks in the USA. And according to the Lewnard and Grad, the resurgence may be due to waning protection from the mumps portion of the MMR vaccine.
The researchers reviewed six studies that had examined mumps vaccine effectiveness to answer two important questions about the vaccine:
- Is the mumps vaccine less effective against emerging and circulating strains of the mumps virus?
- Or does the protection provided by the mumps vaccine wane over time?
The researchers were able to answer the question and more about the mumps vaccine which should be helpful in how the CDC and ACIP move forward with potentially new recommendations.
First, the authors determined that the mumps vaccine was effective in providing broad protection against all of the different circulating strains of the mumps virus. This result itself refutes the oft-repeated claim that the mumps vaccine portion of the MMR vaccine is “useless” against newly mutated mumps virus strains (see Note 1).
Second, the researchers estimated that the protection lasts, on average, about 27 years. In addition, about 25% of vaccinated individuals will lose protection and be at risk for mumps in about eight years. About 50% will be at risk in about 19 years. And 75% of people will be at risk within 38 years. In other words, there is substantial variation as to the timing of waning immunity of the mumps vaccine.
As a result, Lewnard and Grad surmised that the mumps vaccine portion of the MMR induces a shorter-lasting immune response than either the measles or the rubella components. Their full conclusion was:
Routine use of a third vaccine dose at 18 years of age, or booster dosing throughout adulthood, may be a strategy to prevent mumps re-emergence and should be assessed in clinical trials.
I would probably add that there is probably some research into developing a new mumps vaccine (which could be a part of a revised MMR vaccine or given separately) that improves the immune response. However, a third dose probably should be recommended. In fact, ACIP, which is a panel of medical and public health experts who meet three times a year to provide vaccine recommendations to the CDC, did recommend the use of a third dose during mumps outbreaks. However, and this must be stressed, we don’t have any research that tells us how long a third dose might last.
The authors described data from the US military, where newly inducted soldiers, sailors, and officers are given an MMR vaccination, irrespective of previous vaccination status (see Note 2). Since beginning this policy, the US military has not experienced any mumps outbreaks, despite most military personnel are in close quarters much of the time. If this additional dose didn’t work, a mumps virus can fly through an army base or aircraft carrier rather quickly.
And there’s one more thing the authors stressed – although the mumps vaccine may not be perfect in long-term immunity, it actually does a good job of preventing many of the complications I mentioned above. So even if the vaccinated individual contracts mumps, the illness itself is milder.
Despite the claims of the anti-vaccine world, mumps is not rare and it is relatively dangerous, for both children and adults. Also, the myth that a “natural immunity” against mumps, by catching the disease as a child, is not supported by robust epidemiological evidence. Even if that were true, the risk of complications from the disease is too serious to ignore.
Yes, this research provides us with powerful evidence that the mumps vaccine is not perfect, and its immunity wanes over time. But nowhere in this study is there any data or conclusion that the mumps vaccine is completely ineffective. Only those who fall for the Nirvana fallacy, that is, if the vaccine isn’t perfect, it must be useless, will reject the vaccine.
What this study really tells us that we should probably implement a third dose of the MMR vaccine (which also may help improve the long-term effectiveness of the measles component). And it tells us that the vaccine, despite its long-term issues, still provides a high level of immunity, while reducing the complications of measles. I know the anti-vaccine crowd will completely misinterpret and misuse this article to further their agenda, but any real analysis of the full article will lead you to understand the facts.
The only conclusion one can make is that the mumps vaccine, as a part of the MMR vaccine, is incredibly powerful in preventing mumps short- and medium-term, and there is no reason to forgo it. Given that the MMR vaccine is extremely safe (no, it does not cause autism) while protecting against three serious diseases, including mumps, simple math tells us that its benefits far outweigh the risk.
- I’ve noticed that people seem to have a misunderstanding about how viruses mutate. Forgive me for oversimplifying, but the immune system recognizes one antigen on a virus – one out of possibly a few dozens that are on every virus. Vaccines are developed to target the most stable antigen on a virus, an ongoing goal for preventing viruses that mutate quite a bit like the flu. Just because the mumps virus mutates, the vaccine still induces the immune system to recognize parts of the virus that hasn’t mutated. Also, the mutation in the virus may not actually be sufficient to cause the immune system to not recognize it. However, as the mumps virus does mutate, especially in the targeted antigens, the immune response may decline as it becomes “harder” for the immune system to recognize the mutation. I hope this basic explanation assist in understanding how vaccines and mutated viruses work.
- Despite the myths of the anti-vaccine zealots, exemptions to vaccinations in the military are rare and very difficult to receive. Saying that you don’t “believe” in vaccines will not get you very far. And using some unethical physician to get you a bogus medical exemption isn’t going to pass muster, and possibly get you summarily dismissed from the military.
- Lewnard JA, Grad YH. Vaccine waning and mumps re-emergence in the United States. Science Translational Medicine, 21 Mar 2018: Vol. 10, Issue 433, eaao5945. DOI: 10.1126/scitranslmed.aao5945.
- Marin M, Marlow M, Moore KL, Patel M. Recommendation of the Advisory Committee on Immunization Practices for Use of a Third Dose of Mumps Virus-Containing Vaccine in Persons at Increased Risk for Mumps During an Outbreak. MMWR Morb Mortal Wkly Rep. 2018 Jan 12;67(1):33-38. doi: 10.15585/mmwr.mm6701a7. PubMed PMID: 29324728; PubMed Central PMCID: PMC5769794.