On March 19, in the midst of a chickenpox outbreak in his state, Kentucky Gov. Matt Bevin said in a radio interview that he had not vaccinated any of his children against the disease, choosing instead to purposely expose his kids to an infected person to get chickenpox — a practice that public health officials say is dangerous.

In the course of the interview, Bevin made several other false or misleading statements:

He said that the people catching and spreading chickenpox had been vaccinated, calling this an example of irony. Some outbreaks include more vaccinated than unvaccinated people, but that’s an expected outcome. Vaccinated people are far less likely to develop the disease and are usually less contagious if they do.

Bevin incorrectly said that natural chickenpox infection in childhood “will have 99.999 percent no long-term [repercussion] on you.” Shingles, a disease caused by reactivation of the chickenpox virus, is a possibility for anyone who has had chickenpox.

He also falsely claimed that people who are vaccinated against chickenpox “need to keep getting boosters.” There is no evidence that boosters are needed after a person receives the two recommended doses of the vaccine.

Bevin made his comments during an interview with WKCT, a talk radio station in Bowling Green, Kentucky (the interview starts approximately an hour-and-a-half in). According to his campaign website, Bevin has nine children between the ages of 5 and 16. His office did not reply to our request for additional comment.

We’ve written about some of these ideas before. But there are several unusual aspects of chickenpox, or what doctors call varicella, that are worth discussing in more detail.

The governor’s statements also followed news of a Catholic high school student filing a lawsuit against the Northern Kentucky Health Department because of a moral objection to the chickenpox vaccine, which is produced in cells derived more than half a century ago from voluntarily aborted fetal tissue. The student attends a private school where at least 32 students have fallen ill in a chickenpox outbreak.

We’ll explain how the chickenpox vaccine is made, and why the Catholic Church has told its members that getting the vaccine doesn’t go against doctrine.

Deliberate Exposure Is a Bad Idea

Here’s what the Kentucky governor said about his experience with his kids’ cases of chickenpox:

Bevin, March 19: Every single one of my kids had the chickenpox. They got the chickenpox on purpose. Because we found a neighbor that had it and I went and made sure every one of my kids was exposed to it, and they got it. They had it as children. They were miserable for a few days, and they all turned out fine.

Eugene Shapiro, a professor of pediatrics and epidemiology at the Yale School of Public Health, said that in the past, some doctors recommended so-called chickenpox parties, with the idea of making sure a person gets chickenpox as a child, and not as an adult, when the disease is usually much worse.

But that was before the vaccine became available. Now that there’s a vaccine that protects against the disease, Shapiro said deliberate exposure is “foolish to do.”

That’s because while most kids who get chickenpox are fine after a few days of itching and scratching, there can be complications, including serious skin infections, brain inflammation and even death.

Chickenpox is caused by the varicella-zoster virus, or VZV, and typically involves a blister-like rash, along with fatigue, fever, headache and loss of appetite.

Prior to the vaccine, nearly all Americans — about 4 million annually — came down with the disease, usually in childhood. In the early 1990s, before the first vaccine was licensed, around 12,000 people were hospitalized and between 100 and 150 died every year.

While chickenpox is more dangerous to immunocompromised people, most of the deaths, Shapiro said, were in previously healthy people with fully intact immune systems.

The Centers for Disease Control and Prevention “strongly recommends against” chickenpox parties or other events in which parents intentionally expose their children to chickenpox. “There is no way to tell in advance how severe your child’s symptoms will be,” the CDC’s website warns. “So it is not worth taking the chance of exposing your child to someone with the disease.” The best protection, the agency says, is vaccination.

All of Bevin’s children are young enough to have benefited from the chickenpox vaccine, which first became available in 1995 and was recommended by the CDC in 1996. In 2006, the CDC changed its recommendations to include two doses, one at 12 to 15 months, and a second between the ages of 4 and 6.

Who Gets Chickenpox

Bevin also misleadingly pointed out that cases of chickenpox often occur in people who have been immunized.

Bevin, March 19: Here’s the irony. So many of these people that are getting the chickenpox were vaccinated for it. It’s not being spread by the kids who didn’t have the vaccination.

We contacted the Northern Kentucky Health Department to find out how many of the 32 students in the current outbreak had been vaccinated, but the department declined to provide more information. So we don’t know the specifics in this case.

Nevertheless, chickenpox outbreaks can happen in highly vaccinated populations and sometimes a larger proportion of sick people will have been vaccinated. But as we’ve explained before, that doesn’t mean immunization makes you more susceptible, or more likely to spread the disease.

Because vaccines don’t work 100 percent of the time, and the vast majority of children are vaccinated in the United States, it’s entirely possible for more vaccinated than unvaccinated people to get chickenpox.

There’s no irony involved — just math.

The chickenpox vaccine is highly effective, but isn’t perfect. According to the CDC, one dose prevents about 85 percent of people from getting even a mild case, and protects nearly all people from having a severe case. Two doses provide even more protection.

Chickenpox can be spread by anyone with the disease — vaccinated or unvaccinated — but a CDC study found that because vaccinated people are more likely to have a more mild illness with fewer infectious skin lesions, they are also usually less contagious.

Boosters

The governor also erred when he described the long-term immunity of natural chickenpox infection and contrasted that with immunization.

Bevin, March 19: And the odds of getting chickenpox again, if you’ve already had it naturally as a child — where it will have 99.999 percent no long-term [repercussion] on you if you get it naturally — your odds of ever getting it again are slim. But now they’re finding that you need to keep getting boosters if you’re inoculated against it. It’s absurd.

Bevin’s basic claim — that natural chickenpox infection almost always provides good, lifelong immunity — is accurate. But he’s wrong that natural infection won’t have effects on a person later in life, and that one needs to “keep getting boosters” if vaccinated.

The booster idea probably stems from the shift from one to two vaccine doses, which the CDC recommended in 2006. At the time, an unexpected number of outbreaks were still happening in places with good vaccine coverage, so public health officials decided to add a second shot.

And indeed, two doses appear to have largely solved that problem. Surveillance studies have found that since the introduction of the two-dose program, outbreaks and the number of chickenpox cases, hospitalizations and deaths — which had already fallen dramatically with the one-dose vaccine — tumbled further.

Although it isn’t known how long vaccinated people are protected from chickenpox, there is no indication that boosters beyond the second recommended shot are needed to preserve immunity.

Shingles

The larger problem with continued immunity is actually shingles, or herpes zoster, which, like chickenpox, is also caused by VZV.

Anyone who has had chickenpox or who has received the vaccine, which is a live but attenuated form of the virus, can get shingles.

After initially causing chickenpox or triggering immunity, VZV can hide out, dormant, in neurons scattered throughout the body. For the most part, the virus lies low and doesn’t do much. But the virus occasionally reactivates. And if a person’s VZV immunity has declined, either because of age or other factors, the virus can cause a chickenpox-like illness that unfortunately, is usually much more painful.

With shingles, a person develops a painful and itchy rash, typically on just one side of their body. After the rash clears, some patients experience continued and sometimes debilitating pain in the rash area that can last for weeks, months and even years. This is called postherpetic neuralgia, or PHN, and is the most common complication of shingles.

According to the CDC, nearly one in three people develop shingles at some point in their lives. As Shapiro explained, the waning immunity that is responsible for shingles happens “whether or not you get the vaccine.”

In fact, people who have been vaccinated are at a lower risk of developing shingles as children — another benefit of immunization.

There is a concern, suggested by some mathematical modeling, that as more people get vaccinated and there are fewer cases of chickenpox, there will be less natural boosting in the population, which might lead more adults to develop shingles because their VZV immunity will decline more quickly.

But Shapiro told us this was “purely theoretical” and has never been shown.

In the United States, multiple CDC studies have found that while shingles cases have gradually risen over time, the increase began before the chickenpox vaccine rollout, and there hasn’t been an acceleration in the increase since the vaccine came out. The CDC also notes that other countries have observed an uptick in shingles cases, even though they do not have chickenpox vaccination programs.

Shapiro explained that the lack of chickenpox exposures might not be a problem because the virus likely reactivates periodically without causing any disease, in effect producing its own exposures.

“Your immune system sees it and reacts and controls the infection,” said Shapiro. “And it also gives you a boost.”

But even if chickenpox vaccination did have a slight negative impact on shingles, Shapiro said there’s another fix for that: the shingles vaccine.

Two doses of the CDC’s preferred vaccine protects about 90 percent of people from developing shingles and is recommended for people ages 50 and over.

Moral Objection to the Vaccine

The impetus for the governor’s chickenpox comments was a lawsuit brought by a Catholic high school student attending a school experiencing a chickenpox outbreak.

The student, Jerome Kunkel, alleges that the Northern Kentucky Health Department violated his freedom of religion by preventing him from playing basketball because he refused to get the chickenpox vaccine. The Cincinnati Enquirer reported that according to the lawsuit, Kunkel is opposed to the vaccine because it is made in cells that originally came from aborted fetal tissue.

According to letters sent to parents, the health department on Feb. 21 decided to cancel all extracurricular activities, including sports, at the school until the outbreak resolved. Later, on March 14, the department barred any students without proof of vaccination or immunity from attending school. As of that date, 32 students, or 13 percent of the student body, had been affected by the outbreak.

The health department said in a statement that its actions were a “direct response to a public health threat and [were] an appropriate and necessary response to prevent further spread of this contagious illness.”

We won’t go into the legal arguments of the case, but we will share the facts on how the chickenpox vaccine is made.

The two licensed chickenpox vaccines in the U.S. are made of live, weakened virus that, according to their package inserts, is grown in either one or two human cell strains. The cell strains, known as MRC-5 and WI-38, are fetal cell strains that were created from a bit of lung tissue from two different aborted fetuses in the 1960s.

Because VZV primarily infects humans, and these human cells replicate easily in culture, it is possible to grow a large amount of virus with them.

Vaccine production today is linked to abortion only in the sense that it uses the cell strains created half a century ago from those two abortions, which were voluntary and not performed to create vaccines. Vaccines are not grown in aborted fetal tissue, and as the Children’s Hospital of Philadelphia’s website explains, there is no ongoing need to use other fetal cells.

The vaccines also do not contain any fetal cells, although it’s possible an incredibly small amount of fetal cell DNA could end up in the vaccine after purification.

Recognizing this distant link to abortion, and the benefits of vaccines to public health, the Catholic Church has told its congregants that chickenpox vaccination does not violate its teachings.

The Pontifical Academy for Life, for example, stated in 2005 that Catholics should always seek out alternative vaccines, but if they do not exist — and there is no such alternative for chickenpox — then people may use them.

The church also requested that Catholics register a complaint with vaccine manufacturers to push for an alternative in the future.

More recently, after vaccination rates fell in Italy, the Pontifical Academy for Life was even more explicit about this advice.

“The technical characteristics of the production of the vaccines most commonly used in childhood lead us to exclude that there is a morally relevant cooperation between those who use these vaccines today and the practice of voluntary abortion,” the academy wrote in a July 2017 note. “Hence, we believe that all clinically recommended vaccinations can be used with a clear conscience and that the use of such vaccines does not signify some sort of cooperation with voluntary abortion.”