In 2019, the United States saw the largest number of measles cases since 1992, and the vast majority occurred in people who had not been vaccinated against the disease. Like outbreaks of most vaccine-preventable diseases, one of the principal contributing factors was an easy ability for parents against or hesitant about vaccinations to obtain exemptions for their children from rules requiring that kids be vaccinated before attending school.
The slight silver lining to outbreaks like the ones this past year, though, is that they are often closely followed by new proposed laws that make those exemptions harder to get, according to a new analysis published today in the journal *JAMA Pediatrics*.
“We saw a clear signal where more disease outbreaks prompted legislators to propose bills that would limit the ability to exempt,” says study author Neal Goldstein, an assistant research professor of epidemiology at Drexel University.
Last year, Goldstein and his colleagues published a study that looked at all vaccine exemption legislation proposed on the state level, and classified each one as either a pro-vaccination policy, which would limit exemptions, or an anti-vaccination policy, which would relax rules around exemptions.
“We saw a concerning trend at a state level that there were more anti-vaccination bills than pro-vaccination bills,” he says. Looking closely at the breakdown, though, the researchers started thinking about what factors would drive legislators to propose the different types of bills. For this new analysis, they looked at the rates of vaccine preventable diseases between 2010 and 2016 alongside proposed bills—and found that increases in the number of diseases in a state were associated with more pro-vaccine laws being proposed.
“It was a positive finding, and showed that there are some mechanisms that prompt legislators to introduce these bills,” Goldstein says. “We did not see the flip side: if there were lulls, fewer outbreaks, we did not then see legislators trying to slip through legislation that would be anti-vaccination. So that was positive.”
The study did not determine why the relationship between outbreaks and pro-vaccination laws occurs, but it may be that these diseases prompt media attention and increase awareness of the importance of vaccination—which may drive advocacy and legislative response. The same mechanism might also drive a relationship between disease outbreaks and increased vaccination rates, which has been seen in previous studies. “[Outbreaks] could motivate people who were hesitant to get their kids or themselves vaccinated,” Goldstein says. “It’s a question of what’s the end goal you’re looking at: to prompt parents to vaccinate, which is a direct connection, versus and indirect legislative response.”
Proposals for pro-vaccine legislation aren’t a magic bullet to prevent outbreaks—especially since they’re only happening after people are already sick. “It takes disease for action to occur,” Goldstein says. In addition, just because legislation is proposed does not mean it will actually make it into law. But reducing vaccine exemptions is an important way to improve vaccination rates, he says, so it’s still best to understand how and why laws around those exemptions are put in place.
The next step, Goldstein says, would be to take a closer look at the reasons that bills were introduced, which may offer a window into ways that scientific and public health evidence are incorporated into state-level legislation. “This could be for any health-related bill,” he says. “It’s important for us to understand the mechanisms that prompt legislative action on public health related issues.”