In fall 2019, before anyone had ever heard of COVID-19, California legislators were trying to pass a bill aimed at increasing childhood vaccination. Five years previously, someone at Disneyland had set off a measles outbreak that infected more than 100 people, mostly unvaccinated, in the state — as well as in six other states, Canada and Mexico. The incident galvanized legislators and led to a series of laws aimed at curtailing the religious and philosophical exemptions that allowed parents to avoid getting their kids vaccinated before sending them to school. Take the exemptions away, the thinking went, and vaccine rates would rise. But the level of vitriol that enters politics when you try to mandate vaccines can be … intense.

“The California Senate had to be evacuated because someone took — and this is more detail than you want — a cup full of menstrual blood and hurled it onto the Senate floor,” Alison Buttenheim, a professor of nursing and health policy at the University of Pennsylvania, told me.

Today, things are similarly tense. COVID-19 vaccination requirements are taking effect across the country. Universities are requiring students to get vaccinated. Businesses are mandating vaccines for employees and customers. States, cities and the U.S. military have made COVID-19 vaccination a must for public employees. But, as in California, the pushback has been fierce, with protests, fake vaccine cards and outright bans on the mandates in some states.

Simply enacting a law or regulation mandating vaccines isn’t enough. California ended up spending years cleaning up loopholes that parents used to get out of vaccinating their kids. The fact that the California legislature was still tinkering with the state’s vaccination laws in 2019 says a lot. To this day, the state medical board is dealing with physicians who were willing to write thousands of bogus medical exemptions.

Read the full article about vaccine mandates by Maggie Koerth at FiveThirtyEight.