They’re considered one of mankind’s greatest medical achievements, yet people have balked at vaccines almost since the time of the first vaccination.

In the 1800s, people protested in the streets of Victorian England after the British government began requiring citizens to get the first vaccination — against smallpox.

Many opponents mistrusted doctors and were wary of a medical treatment they didn’t understand.

More than a century and a half later, there’s still an undercurrent of vaccine dislike and distrust in the United States. That’s illustrated by the measles outbreak that started in December at Disneyland. Many of those who got and spread the illness hadn’t gotten the childhood shots.

Overall, vaccination rates for kindergarteners have held steady. But increasing numbers of families have refused vaccination in certain communities.