MMR vaccine prevents far more risks from measles, mumps, and rubella than it causes

Measles, mumps, and rubella are viral infectious diseases that were very common among children before the vaccines became available in the 1960s.

In most cases, these diseases resolve on their own without causing long-term complications. This has led some people to perceive them as benign, a misconception that has been likely reinforced by years of narratives downplaying the risks associated with these infections.

In January 2025, such narratives gained momentum on social media, spurred by a measles outbreak in Texas, U.S., which began in late January 2025. As of 14 March 2025, Texas health authorities had confirmed 279 cases, 36 hospitalizations, and one death, over 99% of them in undervaccinated communities.

Amid this situation, political commentator and TV host Candace Owens shared on Facebook an episode of her 2023 series “A Shot in The Dark” dedicated to the measles, mumps, and rubella (MMR) vaccine. What Owens’ website describes on Google’s search results as a “series for in-depth vaccine information” is in reality a catalog of vaccine misinformation, in line with multiple false and misleading claims about childhood vaccination that Owens made in the past.

The MMR vaccine episode specifically revolved around the idea that the MMR vaccine poses more risks than the diseases it prevents. To support this narrative, the episode rehashed old, debunked myths linking the MMR vaccine with autism and childhood mortality. These common anti-vaccine talking points have no scientific basis, as we will show below.

Vaccines don’t cause autism

Autism spectrum disorder comprises a variety of neurodevelopmental disorders characterized by difficulties with social interaction and communication. Extensive research has shown that vaccines, including the MMR vaccine, don’t increase the risk of autism.

The origin of this myth is a now-retracted study by physician Andrew Wakefield published in The Lancet in 1998, which the MMR vaccine episode also invoked. The study was eventually shown to be fraudulent and the British Medical Council banned Wakefield from practicing medicine. However, the consequences of the infamous study persist today.

Studies in twins indicate that autism has a strong hereditary component^[1]. While non-genetic factors are also believed to contribute to the risk, vaccination isn’t one of them. Instead, factors that may play a role include parents’ advanced age, certain medical conditions in the mother, exposure to air pollution and certain pesticides, and prematurity or birth complications that deprive the baby’s brain of oxygen.

Autism diagnoses have indeed risen globally in the past decades, particularly in high-income regions like the U.S.^[2]. This rise coincided with the introduction of newly-developed vaccines in the immunization schedules of the U.S. and many other countries. But this correlation isn’t the smoking gun the episode claimed it to be, because the sole fact that two events occurred in parallel doesn’t imply that one caused the other.

As explained above, studies don’t show any link between vaccination and autism. Instead, the rise in autism is most likely the result of increased awareness, improved screening methods, and changes in diagnostic criteria that have broadened the definition of autism over the years. This has resulted in better diagnoses, enabling doctors to identify cases that may have previously gone undiagnosed or misdiagnosed.

MMR vaccination in Japan: a cautionary tale

Another argument frequently used to attack vaccines is that their side effects increase mortality. Following this narrative, the MMR vaccine episode implied that low childhood mortality in Japan is somehow related to the country’s vaccination policies, including not using the MMR vaccine.

The MMR vaccine is a combined vaccine that contains live, weakened forms of the measles, mumps, and rubella viruses. These weakened viruses induce immunity but can’t cause disease in people with a properly functioning immune system. The effectiveness of two vaccine doses is around 96% against measles, 86% against mumps, and 89% against rubella.

The belief that avoiding the MMR vaccine or vaccination in general reduces childhood mortality is baseless. Global data shows that vaccination reduces childhood mortality. And while Japan doesn’t mandate vaccines, it does recommend vaccination against multiple infectious diseases including measles and rubella, and the levels of vaccine coverage are similar to those in the U.S.

Data from the United Nations shows that Japan’s infant mortality rate is indeed lower than that of the U.S. However, scientific evidence doesn’t support the belief that this difference is related to vaccination policies. A 2005 study by the U.S. National Center for Health Statistics found that a high number of preterm births is a major factor contributing to infant mortality in the U.S.^[3,4].

In addition, research indicates that socioeconomic factors and racial disparities also have a significant impact on infant mortality^[5,6], and that socioeconomic inequalities might be at least partly driving the high infant mortality rate in the U.S. Thus, infant mortality in the U.S. is highest among Native American and Black infants, a disparity that is associated with socioeconomic status^[7].

An excerpt of the MMR vaccine episode that circulated on Instagram referred to a 2001 article in the Daily Mail claiming that Japan decided “to ban the MMR vaccine” in 1993 after “a record number [of vaccinated children] developed non-viral meningitis and other adverse reactions”.

This is true. Following the introduction of a locally-produced combination MMR vaccine, authorities saw a higher-than-usual rate of aseptic (non-bacterial) meningitis (inflammation of the outer protective layer of the brain) in vaccinated children in Japan. In response to this, the Japanese government replaced mandatory vaccinations with a schedule that classifies vaccines as “recommended” routine immunizations or “voluntary” vaccines in 1994^[8]. The combination MMR vaccine was removed from the schedule. Instead, separate vaccinations against measles and rubella were recommended, while mumps vaccination became voluntary^[9].

But there’s more to this story than Owens let on, as a 2018 article on the website Vaxopedia explained.

The increased risk of aseptic meningitis was specifically associated with a mumps strain (Urabe) present in the Japanese MMR vaccine^[10]. While cases of aseptic meningitis following MMR vaccination occurred more frequently in Japan than in other countries using a different strain, the rate was still very low.

Furthermore, the case of the MMR vaccine in Japan is a reminder of why vaccines are still necessary. Concerns over MMR vaccine safety led to a gap in vaccine coverage in Japan that translated into periodic measles, mumps, and rubella outbreaks in the following decades^[11]. Later studies found that the risk of aseptic meningitis in children who got mumps was 25 times higher (1.24%) than after MMR vaccination (0.05%)^[12].

The consequences of Japan’s changes in childhood vaccination policies are still visible today. Voluntary mumps vaccine coverage remains very low in Japan, which results in mumps outbreaks every four to five years^[13-15]. One factor that might contribute to this low coverage is that voluntary vaccines require families to cover the vaccination costs out-of-pocket. For this reason, some local governments have implemented subsidization programs to incentivize mumps vaccination^[16].

What are the risks of measles, mumps, and rubella?

One strategy commonly used by those opposing vaccination is to downplay the health threat posed by infectious diseases.

The MMR vaccine episode did so by arguing (timestamp 28:00) that measles, mumps, and rubella were actually “never even risky” because few people died from them before the vaccines became available. Owens cited a 2007 article published in JAMA showing that measles caused the highest mortality of the three, with “only” around 500 reported deaths every year^[17].

Arguing that a disease is only dangerous if it kills many people is a fallacy that misrepresents reality. While it is true that measles, mumps, and rubella aren’t as lethal as other infectious diseases like Ebola, this doesn’t mean they aren’t dangerous. Death isn’t the only adverse outcome of a disease, and measles, mumps, and rubella can lead to many non-fatal but still serious complications. Moreover, they are highly contagious diseases that can quickly spread in undervaccinated populations, causing large outbreaks.

Measles typically causes cold-like symptoms followed by a red, blotchy, and non-itchy rash. In most cases, the rash fades away in about a week without any major problems. But even in mild cases, measles infection can weaken the body’s immunity, leaving the person more vulnerable to other infections for months or even years.

About 3 in every 10 people infected with measles develop complications—either from measles itself or from secondary infections—that can result in problems as serious as deafness, pneumonia, and brain swelling. Complications are more likely in small children and pregnant women^[18]. Overall, about 20% of the people infected with measles require hospitalization, and roughly 1 in every 1,000 dies.

Rubella symptoms are similar to those of measles, although usually less severe and with a rash that can be itchy and fades away quicker. While rubella is usually mild in children, it is particularly dangerous for pregnant women, especially during the first trimester. The reason is that the infection can easily pass from the mother to the fetus, increasing the risk of miscarriage and stillbirth.

In addition, approximately 85% of newborns whose mothers had measles during early pregnancy develop congenital rubella syndrome. This condition causes developmental problems that can result in loss of hearing and eyesight, as well as damage to multiple organs, including the heart and the brain.

According to the non-profit U.S. National Foundation for Infectious Diseases, during the last major rubella epidemic in the U.S. in the 1960s, 11,000 pregnant women lost their babies, 2,100 newborns died, and 20,000 babies were born with congenital rubella syndrome.

Mumps causes painful swelling of the salivary glands located between the ears and jaw (parotid glands), which makes the person’s cheeks puff like “chipmunk cheeks”. Complications from mumps are infrequent but can be serious, resulting in problems such as deafness, brain swelling, and meningitis.

No specific treatment exists for measles, mumps, or rubella; once a person is infected, the disease must run its course. Only vaccination can prevent the serious complications and deaths that these diseases cause.

How do the risks of MMR vaccination compare to those of the diseases it prevents?

Widespread vaccination has been key for eliminating measles and rubella from over 80 countries^[19] and considerably reducing the number of mumps cases globally^[20].

However, effectively preventing the spread of these diseases requires that at least 95% of the population be vaccinated. Owing to a decrease in vaccine coverage, measles outbreaks have increased globally in recent years, causing an estimated 100,000 deaths in 2023, mostly children younger than 5 years. Vaccine misinformation exacerbates the risks that these diseases pose.

Like all vaccines, the MMR vaccine carries a small risk of side effects. However, these are generally mild and short-lived, including soreness at the injection site and mild fever. Measles and rubella-containing vaccines can also cause some children to develop a mild rash that isn’t contagious.

Serious reactions to the MMR vaccine can occur but are uncommon. These can include severe allergic reactions (anaphylaxis) and immune thrombocytopenia, an autoimmune reaction that causes the body to attack its own platelets. In rare cases, measles-containing vaccines can also lead to febrile seizures (convulsions caused by high fever). Although they may seem alarming, this type of seizures is unlikely to harm the child or cause long-term effects.

However, these potential risks always need to be viewed within the context of the vaccine’s benefits.

As the cases of aseptic meningitis in Japan illustrated, many of the risks associated with MMR vaccination are much higher after infection than after vaccination. For example, the risk of immune thrombocytopenia is at least eight times higher after measles or rubella infection than after MMR vaccination. Likewise, febrile seizures are about 2.5 times more likely after measles infection than after receiving the MMR vaccine.

In summary, vaccination is the most effective way of preventing measles, mumps, and rubella and their associated complications. Such complications aren’t just limited to deaths but also include many non-lethal but disabling sequelae. While serious reactions to the MMR vaccine can happen, this risk is small, and vaccination prevents far more complications than it causes.

REFERENCES

• 1 – Tick et al. (2015) Heritability of autism spectrum disorders: a meta-analysis of twin studies. Journal of Child Psychology and Psychiatry.
• 2 – Li et al. (2022). Global, regional and national burden of autism spectrum disorder from 1990 to 2019: results from the Global Burden of Disease Study 2019. Epidemiology and Psychiatric Sciences.
• 3 – Delnord et al. (2018) Variations in very preterm birth rates in 30 high-income countries: are valid international comparisons possible using routine data? BJOG.
• 4 – MacDorman et al. (2010) Behind International Rankings of Infant Mortality: How the United States Compares with Europe. International Journal of Social Determinants of Health and Health Services.
• 5 – Okui T. (2023) Association between infant mortality and parental educational level: An analysis of data from Vital Statistics and Census in Japan. PLOS One.
• 6 – Lisonkova et al. (2022) Racial and Ethnic Disparities in the Perinatal Health of Infants Conceived by ART. Pediatrics.
• 7 – Saiyed et al. (2025) Black:white inequities in infant mortality across the 69 most populous US cities, 2018–2021. Frontiers in Public Health.
• 8 – Nakano T. (2023) Changes in vaccination administration in Japan. Vaccine.
• 9 –  Ugai et al. (2023) Mumps vaccine hesitancy: Current evidence and an evidence-based campaign in Japan. Vaccine.
• 10 –Di Pietrantonj et al. (2021) Vaccines for measles, mumps, rubella, and varicella in children. Cochrane Library of Systematic Reviews.
• 11 – Saitoh and Okabe. (2014) Recent progress and concerns regarding the Japanese immunization program: Addressing the “vaccine gap”. Vaccine.
• 12 – Nagai et al. (2007) A comparative study of the incidence of aseptic meningitis in symptomatic natural mumps patients and monovalent mumps vaccine recipients in Japan. Vaccine.
• 13 – Kitano T. (2020) Close the gap for routine mumps vaccination in Japan. Human Vaccines and Immunotherapeutics.
• 14 – Ohfuji et al. (2021) Mumps-Related Disease Burden in Japan: Analysis of JMDC Health Insurance Reimbursement Data for 2005–2017. Journal of Epidemiology.
• 15 – Takeuchi et al. (2024) Mumps vaccination and immune status among Japanese university students: A multicenter cross-sectional study. Journal of Public Health Research.
• 16 – Miyazaki et al. (2021) Impact of local vaccine subsidization programs on the prevention of mumps in Japan. Human Vaccines and Immunotherapeutics.
• 17 – Roush et al. (2007) Historical Comparisons of Morbidity and Mortality for Vaccine-Preventable Diseases in the United States. JAMA.
• 18 – Khalil et al. (2024) Pregnant women and measles: we need to be vigilant during outbreaks. eClinical Medicine.
• 19 – Raghunathana and Orenstein. (2022) Investing in global measles and rubella elimination is needed to avert deaths and advance health equity. The Lancet Global Health.
• 20 – Galazka et al. (1999) Mumps and mumps vaccine: a global review. Bulletin of the World Health Organization.