Giving Compass' Take:

• Erin Hare explains how California successfully passed a law that requires vaccinations for children attending public schools. Opposition groups asserted that the law would not impact vaccination rates, but would reduce school attendance. In fact, vaccination rates increased and school attendance stayed the same. 

• How can philanthropy help other states follow this model? Why is herd immunity so poorly understood?

• Find out how long it takes to develop a new vaccine.

Measles is a highly contagious and potentially deadly viral infection. Although the MMR vaccine that prevents it is quite effective, some children — including those with pre-existing health conditions, like cancer or compromised immune systems, and those who are younger than 6 months old — cannot receive it. These vulnerable populations rely on herd immunity to protect them. When vaccination levels reach a critical threshold — 83 percent to 94 percent for measles — the high concentration of immune people squelches the spread of the disease, preventing it from reaching large numbers of unprotected people.

The trouble with getting vaccination rates to this critical threshold is that people lack scientific understanding, said University of Bristol professor Stephan Lewandowsky, who studies how prior beliefs influence the acceptance of scientific facts.

Normally, herd immunity puts up roadblocks that keep each new case from being converted into others — if most people are immune, the disease fizzles out before encountering new potential hosts — but with something as contagious as measles, it doesn’t take many parents opting out of immunization before this critical protection mechanism becomes ineffective.

Lawmakers who want to implement stricter vaccination rules could look to California, where a 2014 measles outbreak at Disneyland inspired a billbarring parents who don’t vaccinate their children for religious or ideological reasons from sending those children to public school. The measure faced significant opposition from anti-vaccination activists, but its sponsor attributed its success to two powerful allies: a compelling mathematical model and vocal support from pro-vaccine parents.

Opponents of California’s bill predicted that if it became law, vaccination rates would remain the same while school enrollment would drop. But the opposite turned out to be true, Pan said. After the law went into effect in 2016, vaccination rates hit an all-time high — and school enrollment increased, according to the California Department of Public Health.

Read the full article about vaccines by Erin Hare at FiveThrityEight.