If avoiding a miserable, potentially deadly virus isn't motivation enough to get a flu shot, here's one more reason: American adults sick with flu cost about $5.8 billion last year in medical visits, medication and lost productivity, according to a new study published in Health Affairs.

And it isn't just the flu; the study found that adults sick with a slew of diseases that can be prevented by vaccines collectively cost about $9 billion in 2015. Vaccines can't prevent all illness, but most of that financial burden — $7.1 billion — was caused by people who skipped vaccines, for diseases including influenza and HPV.

Vaccines are one of the most powerful advances in medicine but became mired in controversy nearly two decades ago because of a fraudulent study that suggested a possible link to autism. That paper has been retracted, and the idea has been thoroughly debunked, but the idea hasn't budged in the minds of some people and has even been repeated by Republican presidential nominee Donald Trump. This debate has focused on children, but many adults aren't keeping up to date on recommended vaccinations — and that, the new study argues, is taking a toll on the economy.

The Centers for Disease Control and Prevention estimated that less than half of adults were vaccinated last flu season, a fact that the study's authors see as a major economic, as well as public health, opportunity. The cost of a disease isn't just measured in doctors' visits, drugs or hospitalizations. The researchers also calculated the productivity loss when people must seek care instead of go to work.

Flu wreaked the highest total societal cost, driven by the high number of cases. It was followed by pneumococcal disease at about $1.9 billion.

Getting more people vaccinated won't erase all of this economic loss, because vaccines aren't 100 percent effective. But it could be an important and simple step to take to improve health and reap a measurable economic benefit.

“By highlighting the tremendous financial burden that unvaccinated individuals place on the economy and the health system, we hope that our estimate will spur creative policy solutions,” the authors wrote.

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