The Problem With Vaccines

When a public health intervention is literally too good.

Pictured: Lifesaving. Photo by Ed Us on Unsplash

It’s uncommon that you need to convince someone over the age of 60 that vaccines are a good thing. While there are of course exceptions to this rule, if you ask the people in my father’s generation about whether they think vaccines are good they’ll usually say “hell, yes!”. They can tell you stories about the kid in their year at school who was permanently paralyzed from a case of polio, or the mum next door who lost a baby to whooping cough, or their friend who struggled to have kids after a nasty case of mumps as a child.

But in the decades since we developed childhood vaccines, these diseases have all but disappeared. Measles was famously eliminated in the United States way back in 2000. This doesn’t mean that the disease completely disappeared - the term for that is eradicated - it means that there are no ongoing outbreaks of measles in the country.

Prior to the introduction of the measles vaccine, the disease had a very well-understood trajectory. It’s a famous example of disease modelling that we still use today, because measles outbreaks in an unvaccinated population are remarkably predictable. In most populations, measles has a 2-year cycle where it infects most of the vulnerable children in the first year, then you get a year of low measles rates as more kids are born, then the cycle starts again.

Obviously, the vaccine changed all of that. The United States used to see upwards of 400,000 cases of measles a year in the early 60s. The vaccine was licensed in 1963, and started being given routinely across the country soon after. By 1970, the rates had dropped by more than a factor of 10, and measles was mostly a thing of the past.

Measles cases in the US, by year. Source: CDC. The graphs from the 1971 AJPH article are also very stark, showing how rapid the drop was.

Most parents these days have essentially no idea what measles is. It’s just an old person thing, like how women required their husband’s approval to have a credit card until the 1970s. Parents in 2024 have never heard of a child being permanently disabled or dying after a case of measles, because it’s so very rare these days. This disconnect from the reality of infectious disease makes many of the myths about measles - like the bizarre idea that it’s not a dangerous disease if you’ve got a good diet - much more understandable.

None of the diseases we vaccinate against are innocuous. Measles causes very nasty pneumonia in some children. There’s also a rare complication from measles called subacute sclerosing panencephalitis (SSPE) where the virus infects people’s spinal cord and brain, usually resulting in death. As this 2010 case study of a 22 year old woman from Australia shows, it can happen to otherwise healthy people who have no known risk factors. It’s hard to know precisely how many people get SSPE, but the number is estimated to be around 1 in 10,000 for older kids and 1 in 5,000 if the infection happens before they turn 5. SSPE is extremely dangerous, with a fatality rate north of 90%.

It’s easy to discount rubella - German measles - if you’ve never known someone who had it during pregnancy. Tetanus is an awful disease that almost no one dies of in the US any more because of the vaccine. It’s very hard to be appropriately worried about problems that you’ve never experienced or even heard of outside of history books.

The problem is that vaccines have become a victim of their own success. People who’ve experienced vaccine-preventable diseases understand the cost/benefit equation. There’s even some evidence of this happening, with pre-COVID studies showing somewhat lower vaccine hesitancy in older parents than younger ones. It wasn’t a hard and fast rule, but generally people who knew someone who died of diphtheria understand why the DTaP is such an important immunization.

People who’ve never had that experience simply don’t know what they don’t know.

With all this, it’s not hard to see how we got into a place where the current US administration is openly anti-vaccine. Yes, it’s partially a blowback against COVID-19, but it’s also in my opinion at least partly because people have become divorced from the reality of what infectious diseases can do. People have no idea what a major measles epidemic looks like, so the idea that vaccines are dangerous is much easier to believe than it was in the 1980s.

Given the current US administration’s antipathy towards vaccinations - with one of the world’s most virulent anti-vaccine advocates poised to become secretary of the department of Health and Human Services - it’s quite likely that these preventable diseases will see a resurgence. The parents who have become more worried about vaccine side-effects will once again watch as disease takes years off their children’s lives, and the mood will probably start to shift.

I doubt that the anti-vaccine sentiment will last long in the face of real disease outbreaks. We know how this works, because we’ve seen it before. In 2018, two children died due to incorrectly prepared measles vaccines in Samoa. This lead to a sharp drop in vaccination rates across the country, in part driven by overseas anti-vaccine rhetoric, including an appearance by RFK Jr himself. Predictably, after the vaccination rates fell to 34%, there was a massive outbreak in 2019. In a few short months around 1 in 5 Samoan kids had contracted measles, and dozens had died. The eventual death rate for all infants in the small Pacific island country was nearly 1%. Faced with such tragedy, the government took swift action and by December 2019 vaccination rates were once again well above 90% in Samoa.

It’s unlikely that death rates would be that high in the US. While some consequences of measles happen even in otherwise healthy kids, a big risk factor for severe pneumonia is vitamin A deficiency which is relatively uncommon in high-income countries.

That being said, measles still causes a great deal of ill health and death even in high-income regions. A death rate 10x lower than the Samoan one would still kill thousands of children if there was a major outbreak in the US.

Which brings us back to the problem with vaccines. They are too effective. If no one ever sees the damage that infectious diseases can do, then many people assume they are harm-free. This makes the potential harms of vaccines seem much more problematic than they really are.

I suspect this attitude will be short-lived. If the current US administration gets their wish, and immunization rates plummet across the country, it will fast become obvious why we choose to vaccinate our children. It’s hard to maintain anti-vaccine lies about mercury and autism in the face of PICUs filled with very sick kids.

Anti-vaccine sentiment rarely lasts past the first major outbreak of disease. This wouldn’t be an issue, except the cost is measured in children’s lives.