Some vaccines have been extremely successful.
“If you want to see one of the greatest public health achievements ever, follow smallpox, and how we were able to eradicate it.”
That’s Rich Lakin. He’s the immunization program manager at the Utah Department of Health.
Smallpox was a contagious childhood disease that killed about 30% of the children who contracted it. Due to an effective vaccination campaign, the disease was declared eradicated in the US in 1972 and in the world in 1980 by the World Health Organization.
Eradicated. As in, no longer present anywhere in the world.
Vaccines work best when most people in a population get them. This is because of a concept called herd immunity.
“So herd immunity is the amount of the population that needs to be vaccinated to protect those who cannot get a vaccination,” Lakin said.
Some people have stronger immune systems than others and, therefore, build stronger immunities against a disease when exposed to the vaccine. If a person with a relatively low resistance to the disease only encounters other people who have relatively high resistance, the disease is not likely to spread to that person, since they are not likely to come into contact with anyone who is infected. Because the infection is less able to move through the population when those who do come into contact with it are highly resistant, most people are much less likely to be exposed to it at all. Basically, vaccines hinder the chain of infection.
The number of people in a population that need to be vaccinated to impart herd immunity depends on how contagious the target infection is. Smallpox, which was very contagious, required almost everyone in the population to be vaccinated to provide protection through herd immunity.
“We always kind of put a 95% of the population needs to be vaccinated or at least 90%, somewhere between there,” Lakin said.
Doctors and scientists often use a measure called R-naught to describe how contagious infectious diseases are. If the R-naught value is lower than 1.0, that means each existing infection causes fewer than one new infection. If the R-naught is one, the new infection rate is one-to-one for each existing infection. If the R-naught is higher than one, more than one new infection is likely to arise for each existing infection.
So, for example, the R-naught value for seasonal influenza is estimated to be between 0.9 and 2.1. It’s an infectious disease, it at least replaces itself, and sometimes one infected person can infect more than one person.
Shockingly, the R naught value for measles is between 12 and 18.
Measles is extremely contagious, so the vaccination rate needs to be high enough to effectively impart herd immunity.
Earlier this century, public health officials hoped to eradicate measles in the United States.
“Measles was so close, but now exemptions have increased, now we’re starting to see outbreaks again," Lakin said. "That’s a prime example of herd immunity.”
Kristen Chevrier does not believe that vaccines are effective enough to provide any protection through herd immunity. She is a vaccine-choice advocate, often called anti-vaxxers.
“When you have a vaccine where A) you don’t know if it’s effective or not, you don’t know if it’s working in all people, and B) you know that it wanes, but it’s probably waning at different rates in different people, and you also have an adult population who’s never had boosters, most of them, you cannot have herd immunity under those conditions because you don’t know who has immunity and who doesn’t," she said. "And there’s really no way for you to keep track of that, as far as I can tell.”
Lakin says that some vaccines do wane, but that is not a reason to avoid them.
“So, yeah," he said, "the immunity will wane over 50 years or 40 years because your body hasn’t been exposed to it. So that is why they do recommend boosters in adults.”
All 50 states have laws requiring school children to get some vaccines, including the MMR - the vaccine for measles, mumps and rubella - but they also all provide avenues to get medical exemptions for children who cannot be vaccinated. 45 states also provide options for religious exemptions and 15 states have philosophical exemptions. The religious and philosophical exemptions are often very flexible. Utah allows for all three of these exemptions.
Chevrier does not believe that the recent uptick in measles cases is a concern.
“Measles is cyclical and it has never been eradicated," she said. "I don’t think we’re seeing a huge number of additional outbreaks is what I’m saying.
“You see the thing with measles is, it’s actually a super mild disease or illness - it’s not a disease. It lasts for about a week, and if you have vitamin A, and you have clean living conditions and rest, you usually don’t ever have complications. Where we have the deaths is where there’s a population that doesn’t have clean living conditions, they don’t have access to good nutrition and they don’t have vitamin A. And their lifestyle makes them more susceptible to complications,” Chevrier said.
Lakin disagrees that measles is so easily managed.
“Simply a bunch of hogwash. I’ve always heard people talk about that there’s holistic-type stuff out there that they can take that prevent them from getting any type of infectious diseases, and it’s simply not true.”
He says the effects of measles can be very serious.
“I know at least 1 out of 20 could get pneumonia, which is going to be one of the reasons why they die, because of pneumonia. One out of 1000 that gets it gets the encephalitis, which is swelling of the brain. If it’s swelling of the brain, that means you’re going to have central nervous system problems. Of every thousand children that get it, one or two will die from it. Measles in pregnant women give birth prematurely. Long term complications, they could get permanent hearing loss. So those are just a few of the symptoms.”
Additionally, there was a study in 2005 that found 1 in 10,000 people who have measles develop a disease called subacute sclerosing panencephalitis, or SSPE. This disease causes swelling in the brain in children and young adults six to 10 years after they have measles. There is no cure and it is almost always fatal. A 2016 study indicated that if the patient has measles when they’re a baby, 1 in 609 of the survivors will develop SSPE.
According to the Center for Disease Control, or the CDC, the measles vaccine included in the MMR is 93 to 97 percent effective. The World Health Organization estimates that over 21 million deaths, mostly children, have been prevented because of the measles vaccine since 2000.
Despite this, some parents still worry that unintended side effects from the vaccine may harm their healthy children. In a few cases, those parents may choose not to have their child vaccinated.
“I started doing research and I came to the conclusion that, for my children, that is was probably best not to continue to vaccinate." Chevrier said. "So, let’s see, the fourth one was probably two months when I made that decision, and then I would have had a sevenyear old, would have been the oldest.”
“We’ve got to remember that the anti-vax movement is a small population, very loud, but a small population,” Lakin said. “With exemptions, they are increasing, we saw a half a percent increase, 0.05, between 2017 and 2018. So we are seeing our exemptions increase, just like the rest of the country.”
Despite this increase in parents declining to vaccinate their kids, the rate of MMR vaccination among school-aged children is still over 90% in Utah.
Happily, if rates of vaccination remain high in the communities where non-vaccinated children live, it is unlikely that they will ever be exposed to measles or any other vaccine-preventable childhood disease.