Kentucky Governor Matt Bevin made headlines Tuesday after revealing in a radio interview that he had purposefully exposed his nine unvaccinated children to chickenpox, drawing swift condemnation from health experts.

In case anyone needs a refresher on why you shouldn’t deprive children of safe, potentially lifesaving vaccines or purposefully expose them to serious, potentially life-threatening infections, here’s a quick rundown.

Chickenpox is nothing to mess with

Though most children who get the itchy, highly contagious viral disease go on to recover after a week or so of misery, chickenpox can cause severe complications and even death in some. Complications include nasty skin infections, pneumonia, brain inflammation, hemorrhaging, blood stream infections, and dehydration.

If the infection strikes early in a pregnancy, there’s a small chance it could cause birth defects, including abnormally formed limbs, brain, eyes, and skull, as well as intellectual disabilities. If it strikes just before birth, a newborn has a 30 percent chance of getting a severe form of the disease, which can be fatal.

In addition to newborns, people who have an increased risk of severe complications from chickenpox include teens, adults, pregnant women, and people who have a weakened immune system, such as cancer patients on chemotherapy, transplant patients, and those with HIV/AIDS.

But even healthy children may develop complications. There is no way to determine in advance the severity of the infection.

And the fight’s not over after chickenpox. Then there’s shingles

The same virus that causes chickenpox causes shingles, or zoster. After chickenpox subsides, the virus, varicella-zoster virus (VZV), goes dormant. It hides out in dorsal root ganglia, which are nerves that transmit signals to the spinal cord. VZV can react at any point later in life to cause shingles, which commonly manifests as an incredibly painful, sometimes itchy rash on the trunk of the body.

Shingles is also nothing to mess with, as Ars’ own Managing Editor Eric Bangeman can attest. He battled with the resurgence in the fall of 2015 and described it as “several days of acute misery sandwiched by a couple of weeks of feeling crappy.”

Shingles also has the potential to cause complications. The most common—occurring in around 13 percent or more of shingles cases—is postherpetic neuralgia (PHN), which is persistent pain for weeks, months, or even years in the area of the rash after the rash disappears. There’s also the possibility that shingles could lead to bacterial superinfections on the rash and issues with the eyes that can lead to vision loss, as well as inflammation of the brain or liver, and nerve palsies.

Of course, nearly all of this can be avoided because...

There are vaccines for this

The chickenpox vaccine—aka varicella vaccine—debuted in the US in 1995. It’s safe and highly effective. Two doses of it is up to 98 percent effective at preventing all forms of chickenpox. In the rare cases when a vaccinated person still gets chickenpox, the disease is very mild. The vaccine is 100 percent effective at preventing severe forms of the illness.

In the years before the vaccine was available, there were an average of 4 million cases of chickenpox each year in the United States. This led to an average of 10,500 to 13,000 hospitalizations and 100 to 150 deaths each year, according to the Centers for Disease Control and Prevention. With the availability of the vaccine, cases of chickenpox in 31 monitored states fell 79 percent between 2000 and 2010. Deaths from the disease fell 87 percent between four-year periods before and after the vaccine arrived.

The vaccine contains a live but weakened VZV, which causes a latent infection. This can reactivate later in life to cause shingles. However, in a recent study, children who had been vaccinated for chickenpox had a 79 percent lower chance of getting shingles than those who had gotten chickenpox.

Also, there are now two vaccines to prevent shingles in older adults. The current preferred vaccine is the recombinant zoster vaccine Shingrix, which is more than 90 percent effective at preventing shingles after two doses.

This should make “chickenpox parties” obsolete, if not just dangerous

In the past, some parents may have thought it was a good idea to expose their children to chickenpox on purpose to ensure that they got the disease before they were older, when it is more likely to lead to complications. However, as noted earlier, chickenpox can be severe even in healthy children, and it’s impossible to tell in advance how severe each case will become. Moreover, with the advent of safe and effective vaccines, there’s no reason to subject children to preventable infectious disease that—even in mild cases—causes hundreds of agonizing, itchy blisters along with fever, malaise, and headache.

But it’s not just about your kid

Vaccination protects vulnerable people, including those with who can’t get vaccines due to medical conditions or those who are immunocompromised. Even if the kids at the parties go on to have mild cases and fully recover—as was the case for Gov. Bevin’s children—the parties can keep the virus circulating.

The dangers of allowing chickenpox to keep spreading hit home for Italian politician Massimiliano Fedriga, who came down with the disease last week after opposing legislation that mandated the immunization in school children.

Prominent Italian microbiologist Roberto Burioni responded in a Facebook post, noting that the situation was unfortunate for Fedriga but could have been even more tragic if, for instance, the virus had spread to a fetus or a child undergoing a transplant.

“The only way we have to avoid these tragedies (because they are tragedies) is to vaccinate us all to prevent the circulation of this dangerous virus, which could have hit a much more vulnerable person,” he wrote.