Measles, whooping cough and other diseases thought to have been eliminated decades ago are reappearing in California and other states and health officials worry that widespread resistance to childhood vaccinations raises potential for dangerous outbreaks of infectious illnesses.

A New York Times story by Adam Nagourney and Abby Goodnough reports a measles outbreak at Disneyland infected 42 of the 59 people in California whose illnesses were reported to the state this week. The Center for Disease Control and Prevention (CDC) reported 644 cases of measles in 27 states in 2014, the biggest number since 2000. Before common use of measles vaccine in 1963, the story reports, measles infected three to four million Americans a year and 400 to 500 people died.

Stories by Gary Baum of the Hollywood Reporter document childhood immunization rates as low 57 percent and 68 percent in some in some elite preschools in wealthy neighborhoods, numbers that are on a par with immunization in Chad and South Sudan. And nearly 8,000 cases of whooping cough, including 267 that needed hospitalization, had been reported to the state during the first nine months of 2014. Whooping cough, also called pertussis, once killed thousands of people annually, but introduction of the DPT (diptheria, tetanus and pertussis) vaccine nearly eliminated the disease.

During the current measles outbreak, unvaccinated children have been banned from going to public school in Orange County. A Washington Post Wonkblog identifies Orange County as "ground zero in the current epidemic of anti-vaccine hysteria." California allows parents to avoid vaccinating their children by filling out personal belief exemptions, and Baum reports an alarmingly high number of families in many of the wealthiest communities have made that choice. The CDC recommends vaccinations, some of which need multiple doses, against 14 diseases.

Radio station WBUR in Boston reported on a study showing vaccination rates in some states, including Oregon, West Virginia and Colorado, have dropped below the level required for herd immunity. Thresholds differ based on how infectious different illnesses are. The CDC suggests that threshold is crossed for whooping cough and measles when more than six percent of the population is not immunized. Herd immunity means that where a high percentage of the population is immune, the chance of an infected person meeting a susceptible person is low, so disease is unlikely to spread. Diseases spread rapidly among people who are not immunized.

Some parents worry about discredited research linking vaccines to autism, and some have religious or philosophical objections. The National Vaccine Information Center raises concerns about vaccines and the Times story quotes a spokesperson as minimizing the hazard of rejecting vaccination. Why do many resist? A 2014 AP-GfK survey reports only 53 percent of adults are "very confident" that childhood vaccines are safe and effective. The Post Wonkblog notes wryly that's about the same percentage who think houses can be haunted by ghosts.

The World Health Organization, urging universal immunizations, asserts that vaccines save lives and prevent disability, as well as mitigating severity of many diseases, reducing secondary infections. Some vaccines provide protection against related diseases. WHO says, for instance, that measles vaccination protects against multiple complications including dysentery and bacterial pneumonia.

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Friday, January 23, 2015  1:00PM Eastern