The Vaccine-Preventable Diseases

Critica Begins a New Series About What We Are Vaccinating Against

Part One: MMR

Although a large majority of Americans believe that vaccines are safe and effective, a sizable minority are “vaccine hesitant” and worry about the safety of childhood vaccinations. One reason often cited for vaccine hesitancy is that many of the diseases we vaccinate against are rare in the U.S. today, so new parents have never seen them. Without a mental image of what a vaccine-preventable disease looks like and does, people may have trouble appreciating the risk it poses. If the risk of the disease seems, mistakenly as we will see, negligible, then any alleged risk of the vaccine against it becomes more believable.

         Simply telling people that the risk of a serious reaction to a vaccine is one in several thousand does not have the weight of a single anecdote of a child who has suffered from one of the rare serious adverse side effects.  Similarly, just telling people that a vaccine-preventable disease causes “X” number of serious complications may not be convincing. But seeing children with these conditions is highly persuasive.

One member of the Critica team began his medical career in pediatrics and is old enough to have seen cases of measles, mumps, rubella, and diphtheria. For him, the idea that anyone would hesitate to vaccinate against these diseases is hard to grasp. Recently, he was describing how serious the complications of measles can be to a young parent who had never seen a case. She seemed surprised that measles can be, and still is, sometimes fatal. “I don’t think people my age have any clue what the diseases we vaccinate our children against can actually do,” she said.

         And so we decided to begin a series of articles describing some of the vaccine-preventable diseases, starting here with measles, mumps, and rubella, the targets of the MMR vaccine.  That’s the one, of course, that was once accused of causing autism, a thoroughly false claim that we won’t bother getting into here. Nor can we counter vivid anecdotes of serious vaccine reactions with vivid anecdotes about children with these illnesses because we have none: despite the recent and alarming increases in measles cases in the U.S., it is still uncommon and most pediatricians will go through an entire career without ever seeing a single case of measles, mumps, or rubella.

         We do hope, however, that these short descriptions of vaccine-preventable diseases will serve as a reminder that there is a very good reason we vaccine against them: at very least they make young children thoroughly miserable for a week or more and at worst they cause severe and sometimes fatal complications.

Measles Still Kills

         Measles, also known as rubeola, is caused by a remarkable virus. Remember that all the cells in the human body have genes composed of a molecule called DNA and that DNA is transcribed to RNA, which then begins the process of engineering protein production. The measles virus, on the other hand, has no DNA. It contains only RNA and is therefore called an RNA-virus. The same thing is true of the virus that causes AIDS, HIV. That makes it easier for the virus to incorporate itself into an infected person’s own cells and redirect what they do.

         And just like HIV, the measles virus has the uncommon ability to suppress an infected person’s immune system for months and sometimes longer.

That makes people who get measles susceptible to getting infected with other viruses and bacteria, increasing the risk of serious complications.  

         The measles virus lives in an infected child’s nose and throat and is spread to others by coughing and sneezing. It can actually live in the air of a room where someone coughed for as long as two hours. An infected child can spread measles to other people from four days before a rash appears to four days after it appears. Because measles often starts with symptoms that are similar to the common cold, like coughing, runny nose (coryza), fatigue and loss of appetite, a person can spread it before even knowing they have measles. And spreading it is easy; measles is one of the most contagious viruses known. As many as 90% of people who come in contact with someone with measles will get it.

         The rash is what gives away the diagnosis of measles. Shown in the illustration below, It often starts with little white spots, called Koplik spots, inside the cheeks. A day or two later the characteristic red, bumpy, blotchy, and somewhat itchy rash starts on the face and neck and spreads throughout the rest of the body, all the way to the feet. During this week to ten days of unfolding symptoms, a child with measles feels awful. While it is true that you can only get measles once, that one time is memorable for the patient, who spends the time with watery eyes, coughing, sneezing, feeling very weak, and itchy all over. High fever makes it impossible for the child to do much and kills his or her appetite. If you are a parent with a child who has measles, you are likely to say to yourself “even though I know this is going to go away, I wish my child didn’t have to suffer like this.”

A young, very unhappy looking girl with the rash typical of measles (source: Shutterstock).

         Unfortunately, measles doesn’t always “just go away.” While most children recover completely, others have serious complications. Before the measles vaccine became available, measles killed more than 2 million children every year. That number has been drastically reduced since the measles vaccine was introduced, but unvaccinated children can still succumb to measles. In 2018 there were about 140,000 measles deaths around the world, mostly in children under five years old. For every 1000 children who contract measles, two die. Most of those occur when the measles virus infects the lungs, causing pneumonia, or the brain, causing encephalitis. Measles can be especially devastating for children with suppressed immune systems, including children with cancer. Infants who have not yet been vaccinated against measles are also particularly vulnerable to the serious complications of measles infection.

         Against all of this, it seems clear that vaccinating children to protect them from measles is a very good idea. The measles vaccine is a “live attenuated virus” vaccine, meaning that the naturally occurring measles virus is changed by growing it in cell cultures to a form that is incapable of causing measles but still able to stimulate the immune system to make antibodies against it. If at any point a vaccinated person is exposed to the real measles virus, the immune system will then immediately attack the virus and prevent the vaccinated person from getting sick


The leading cause of death from measles is pneumonia. The measles virus can infect the lung, as seen in this illustration where the white patch in the right lung represents the infection (source: Shutterstock). 

As we mentioned earlier, we are not going to debunk here the completely erroneous claims that the MMR vaccine causes autism or any other damage to the brain or immune system. It is true that there are people who have allergies to all kinds of things and that includes the MMR vaccine. But just keep this in mind: fewer than one in one million people have a serious allergic reaction to MMR vaccine; two out of every 1000 children will die from measles. Consider those odds.

Mumps: A Silly Name for a Serious Disease

         The word “mumps” sounds a bit silly and perhaps encourages people to think of the illness as something that is not very serious. That is, of course, a mistake. The mumps virus belongs to the same family of viruses as the measles virus (the paramyxoviruses) and, like measles, it first infects the nose and throat and is spread mainly by coughing and sneezing. Also like measles, mumps is highly contagious.

         Although rarely fatal, mumps infection can cause serious and sometimes permanent damage. The hallmark of the illness is swelling of the salivary glands, especially the parotid gland. This is very uncomfortable and often painful, but almost always resolves in about a week without complications. More serious is infection by the mumps virus of the testicles, a condition called orchitis. About 10 to 20% of post pubertal boys and men get orchitis with mumps. In about half of those cases, there is permanent damage to some of the internal structures of the testicles, resulting in permanent reductions in sperm count and impaired fertility.

This poor child shows the characteristic swelling of the parotid gland, one of the salivary glands, caused by the mumps virus (source: CDC). 

         Another complication of mumps that occurs in about 10% of infected people is meningitis, an infection of the membrane the lines the brain and spinal cord. Although uncommon, mumps can cause temporary hearing loss and sometimes permanent deafness. In fact, it was once one of the leading causes of deafness in children.

         Swollen testicles, impaired fertility, brain infection, and deafness, then, are all some of the potential complications of having mumps. Doesn’t sound as if most parents would want to take the risk of withholding the vaccine, does it?

Rubella: the German measles

         It is true that rubella (the “R” in MMR) is usually a very mild illness. So mild, in fact that many people don’t realize they have it or think it’s just a routine viral infection.  And that is the problem, because the serious threat from rubella infection (also known as “German measles”) occurs when it strikes a pregnant woman. Because rubella can be so subtle and because people who have it are contagious for a week before the typical rash appears, it is not possible to simply try and keep pregnant women away from someone with rubella. The damage can be done by someone who doesn’t know they have it or to a woman who doesn’t yet know she is pregnant.

         The rubella virus belongs to a different family of viruses that measles and mumps (togavirus), but like them is an RNA-virus. Children with rubella may have fever, runny nose, swollen glands, red eyes, and a pinkish rash. It’s also spread by coughing and sneezing. It goes away by itself in a few days and rarely causes any further complications or damage. So why bother with a vaccine?

         The answer is that rubella infection in a pregnant woman, especially if she is in the first trimester, causes the congenital rubella syndrome. The baby whose mother was infected is born with cataracts, deafness, and heart defects. There may also be problems with other organs, growth retardation, and intellectual disabilities. That is, of course, if a baby is born: rubella infection can also cause miscarriage and stillbirth.

This illustration shows viral particles, like the rubella virus, infecting an unborn fetus. The baby will likely have the congenital rubella syndrome (image: Shutterstock). 

         When the same member of the Critica team who started his medical training in pediatrics was in college in 1973 he got rubella. He didn’t feel that sick, but he had a rash all over his body and went to the student health service. He remembers the doctor there saying, “I’ve seen deaf babies because of German measles, you are going into isolation in the hospital.” One interesting thing about this case is that he was told as a child that a viral illness he had was German measles, but that could not have been possible because you cannot get it twice. Rubella infection was confirmed by a blood test when he got it in college and that means what he had as a child had to have been something else. That’s how easy it is to mistake rubella for a different viral infection and hence to unwittingly spread it to a pregnant woman.

         It is true that if you don’t vaccinate your child against rubella, someone else will suffer the consequences: the newborn of an unvaccinated pregnant woman whom that child infects. It would seem to take a very high degree of self-centeredness and cynicism to use that as the excuse for not administering a completely safe vaccine against rubella to every child.

A Reminder

         We will do this reminder about what the diseases do that we don’t see much of anymore because vaccines prevent them again soon. Next up will be the diseases prevented by the DPT vaccine (diphtheria, pertussis, and tetanus). It will be more harrowing stories of children dying or being born with terrible congenital abnormalities. Next time someone tries to tell you that vaccines hurt children, you might show them this commentary and correct that impression: it is the diseases that vaccines prevent that hurt children.

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