The Loss of Control of Measles in the U.S.: A Harbinger of Bad Things to Come

For the past five years, we have been seeing the impacts of decades of coordinated anti-vaccine, and more generally and more recently, anti-science campaigns on a grand scale. When writing the previous sentence, I initially used the phrase “we have been seeing the end results,” but then I replaced “end results” with “impacts.” That is because, sadly and tragically, I think we are far from the end results that we will watch unfold over the upcoming months and years.

This is a difficult blog post for me to write because by nature, I am an eternal optimist, and that trait is aided and abetted by another trait in that I have a great propensity for being naïve. During the first couple of years of the COVID-19 pandemic, I optimistically and naively believed that (1) the pandemic would be our wake-up call to take infectious disease threats more seriously, and as a result invest more in research and preparedness (the exact opposite is occurring); (2) the clear and mounting evidence would persuade the citizenry and our elected leaders of the value of vaccines and the need to think about treating the circulating air in public buildings as a public health measure in much the way we thought about the need to treat water for public health back in the early 1900s (it didn’t); and (3) those doctors who promoted disinformation would be held accountable or at least fade away from the public light in shame (that largely did not happen).

As of April 17, 2025, the CDC has reported 800 confirmed cases of measles in the U.S. in 25 states: Alaska, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Indiana, Kansas, Kentucky, Maryland, Michigan, Minnesota, New Jersey, New Mexico, New York City, New York State, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas, Vermont, and Washington. The number of actual cases is likely orders of magnitude higher as there are time delays in confirming and reporting cases, not all cases have sought medical care, and there have been reported to be some efforts among some communities to keep cases from being disclosed. Not only are the actual numbers almost certainly far higher, this outbreak is likely far from over. I will be surprised if this outbreak ends before the end of this calendar year and before extending to every state.

There are some interesting demographic data about these confirmed cases:

Under 5 years: 249 (31%)
5-19 years: 304 (38%)
20+ years: 231 (29%)

Percent of Age Group Hospitalized

Under 5 years: 19% (47 of 249)
5-19 years: 7% (21 of 304)
20+ years: 6% (15 of 231)

Many people have the idea that measles would just be an issue for toddlers and preschoolers. But, as one can see, the outbreak is impacting children at all ages, including nursery, pre-school, elementary, middle school, high school, and even college. Some will be surprised by the number of cases in persons over 20 years of age. However, this is easily explained. The U.S. mounted a campaign to eliminate measles through immunization that resulted in measles cases precipitously dropping by 1991 and a certification that measles in the U.S. had been eliminated by 2000. Thus, persons born after 1990 (i.e., 35 years old and younger) who were not vaccinated, would have a fairly good chance of not having been exposed to measles and therefore susceptible to infection now. Further, I would suspect that a fair number of those that are over 20 years of age are also parents. If they were not vaccinated as children, there would be a good chance that they would not vaccinate their children and that many of these parents may have been infected by their children.

Another surprise to some may be that 15 of those over age 20 were hospitalized for measles. I actually am surprised that the number was not higher. Typically, those that are under 5 and those who are adults are the ones at highest risk for severe complications of measles such as pneumonia.

Further, as I have written before, this will not be the end of the health consequences from this outbreak of measles even once it does end. We know that those recovered will experience varying degrees of immune amnesia, meaning that they will lose some degree of their immune protection to other viruses as well as bacteria that they accumulated over the years, and as a consequence, their health risks and mortality rates are higher than the general population for the next few years until that immunity is reconstituted. Further, there is an absolutely dreadful and universally fatal neurological condition (subacute sclerosing panencephalitis) that, though fortunately rare, we are almost certain to see, probably in the next 3 – 7 years, due to the large number of people infected.

Much of what I wrote about above has been discussed with the public about the scale of this outbreak and the health consequences. However, what I have not heard is a discussion about is what other implications this outbreak has for us and our children and grandchildren.

While our focus has been on measles, it is important to realize that this same population of measles-susceptible individuals is also susceptible to rubella (German measles) and mumps since the vaccines for all three viral diseases has been included in a single vaccine – MMR – for their entire lifetime. Infection with measles provides no protection against rubella or mumps. It would not be surprising that measles would be among the first of these viral illnesses to emerge due to its high transmissibility and infectiousness, and the high levels of population immunity required to provide herd immunity (~95%).

I expect that we will see outbreaks of rubella and mumps in the months and years to come for a number of reasons. First, the wide-spread measles outbreak (over 800 reported cases as this time, however, I suspect that the actual number is in the thousands) is a good indicator of the number of children and young adults likely also susceptible to rubella and mumps. Measles is more highly contagious than rubella or mumps, and whereas the head immunity threshold is ~95% for measles (meaning that if a population has less than that number of its members protected against measles by virtue of vaccination or prior infection, then the potential for outbreaks increases significantly), that threshold for rubella is ~85% and for mumps is 85 – 90%. Thus, we expect measles to be the bellwether for disease outbreaks due to lack of herd immunity, but mumps and then rubella are certainly concerns to follow, unless high numbers of those not protected receive the MMR vaccine in response to efforts to contain the measles outbreak. Unfortunately, our federal response to the measles outbreak has not sufficiently focused on MMR vaccination, but rather confusing messages that tout various alternative approaches that we know do not prevent infection by the measles, German measles or mumps viruses.

So, let’s discuss these two other diseases and explain the concerns about their reemergence, if I am correct in my prediction.

Rubella (German measles)

As stated above, measles is the most contagious virus we know. Its reproduction number (R0), meaning the number of susceptible persons who are likely to be infected by one person with infection ranges between 12 – 18. German measles (rubella) is also transmitted by air and quite contagious, but much less so that measles. The R0 for rubella has been difficult to quantify and far ranging in various settings, but commonly believed to be < 5.

Rubella is caused by the rubella virus. Illness is characterized by fever, rash and swelling of the lymph nodes. Rubella is, in most people, a milder illness than measles, however, rubella has been a more common cause of birth defects than measles, and frequently, more severe defects. In fact, rubella has been the most frequent infectious disease cause of birth defects.

Rubella is a vaccine-preventable illness and the vaccine was approved in the U.S. in 1969. It was administered as a single dose vaccine until it was incorporated into the MMR vaccine in 1971 as a two-dose series. Through vaccination efforts, rubella was eliminated in the United States in 2004.

One of the feared conditions occurs when a pregnant mom is infected with the rubella virus, which can then pass to and infect the unborn child. That condition is referred to as congenital rubella syndrome. My fear is that many of the young girls and women who are infected in the current measles outbreak, will not seek vaccination against rubella, and that this will potentially give rise to an increase in congenital rubella syndrome in their future children.

Congenital rubella syndrome (“CRS”) is a constellation of possible manifestations that can include stillbirth, premature labor, brain structural abnormalities, liver involvement and enlargement, jaundice, growth retardation, cataracts, heart disease, and hearing loss. The risk of the fetus developing CRS is estimated to be 80% if the mother is infected with rubella during the first trimester, and this drops to a bit over 50% in the first part of the second trimester and then to 25% if the maternal infection occurs in the last part of the second trimester. CRS is a range of mild defects to severe, with severe occurring in roughly 10-20% of cases of CRS. The infants born to mothers infected in the third trimester can have congenital abnormalities, but they typically are milder and fewer and don’t present as the constellation of abnormalities characterized by CRS.

The last major rubella epidemic in the United States was from 1964 to 1965, and the toll was very significant. An estimated:

• 12.5 million people got rubella
• 11,000 pregnant women lost their babies
• 2,100 newborns died
• 20,000 babies were born with congenital rubella syndrome 

In recent years, we typically have 10 or fewer cases of rubella infections per year and no cases of CRS. Most of these resulted from exposure during international travel or living abroad.

Mumps

The mumps virus is of similar contagiousness to the rubella virus with a R0 of just under 5 (about 4.8).

The mumps vaccine is very effective, however, unlike the measle vaccine which generally results in lifetime protection, the protection from the mumps vaccine does wane after 16 – 51 years, with an average of 27 years. So long as we continue to have high rates of vaccination such that 85 – 90% of the population is protected, older adults should remain at low risk even with waning immunity.

Mumps is generally a mild, though miserable, illness in children in which they experience fever and swelling of the parotid glands (these are salivary glands located over the cheeks just in front of the ears and extending down to the bottom of the jaw giving rise to a chipmunk appearance in children with infection), however, in rare cases, those infected can develop a serious inflammation of the brain requiring hospitalization that can cause death or permanent disability. However, as many as 10% of mumps infections acquired after puberty may cause severe complications including orchitis (swelling of the testicles), meningitis (inflammation of the lining around the brain), and deafness that can be transient or permanent. Orchitis can result in shrinking of the testicle or testicles and at least temporary loss of or decrease in fertility. Girls and women who are infected may develop oophoritis (an inflammation and swelling of the ovaries) and/or mastitis (an inflammation and swelling of the breasts).

In the case of measles and rubella, our concern in future outbreaks would be for those who are unvaccinated or those who are immunocompromised. However, if we do experience outbreaks of mumps in the future, we would be concerned that some young to middle-aged adults, as well as older individuals might be susceptible even though previously vaccinated due to waning immunity. If that happens, I suspect we would institute a third booster of mumps vaccine.

These would be truly sad developments given our previous success and knowledge accumulated over the years.