Whooping cough contained

Two years after pertussis, or whooping cough, killed 10 children and infected 9,000 people in California, a new vaccination law has the disease at an all-time low.

California went all of 2011 and half of 2012 without a single pertussis death, with a rate of less than one case per 100,000 people—more than seven times lower than the national rate, according to California Health Report.

The decrease in pertussis infections is largely credited to a state law requiring children in grades 7 through 12 to get a Tdap booster shot—which covers tetanus, diphtheria and pertussis—before they begin school. Most kids are administered a series of shots before age 7, but recent studies have shown they wear off after about five years.

Pertussis can be a lengthy and painful cough for adults and is potentially deadly for babies too young to get vaccinated.