Even 150 more cases of measles could cost public hospitals in the US $2.1 million, according to a new paper. The research shows that even small drops in the level of vaccinations can have big negative effects.

For a study out today in JAMA Pediatrics, researchers analyzed data from the Centers for Disease Control and Prevention, and estimated what could happen if vaccination rates keep dropping. Right now, 93 percent of kids ages two to 11 in the US are vaccinated against measles, mumps, and rubella. If that number dropped by 5 percent, it would lead to 150 more cases of measles. This might not sound like a lot, but it is actually a three-fold increase compared to the number of cases that exist now, and it could cost over $2 million from local and state public health institutions. (The cost covers things like lab analysis and transportation, for example.) The numbers would be even higher if they took into account people outside of that age range who aren’t vaccinated.

Measles is a highly infectious viral infection that can cause everything from a red trash to brain inflammation. Though two doses of the MMR vaccine is about 97 percent effective in getting rid of the disease, vaccination rates are dropping, in part due to states that allow religious and philosophical exemptions. As a result, there have been outbreaks — just as we thought we had eradicated measles from the Americas. Notably, Minnesota has grappled with 73 cases this year, due largely to people who don’t vaccinate their children because they wrongly believe a debunked theory that vaccination causes autism.

The authors conclude that these results highlight just how important it is to take vaccination seriously, and suggest that politicians consider removing the “personal belief” exemption that is letting people opt out.