Parents in the Santa Monica-Malibu School District should be on alert: The percentage of kindergartners who weren’t vaccinated last year because their parents don’t like the idea of immunization reached more than 14%, well above the level considered safe to keep kindergartners there protected from disease. The number was almost twice as high in the wealthy enclave of Montecito.

If the only children who could fall ill as a result were those who hadn’t been vaccinated, this wouldn’t matter quite as much. It would be, as vaccine skeptics like to say, a personal, parental choice.

But that’s not the way immunity works. Keeping children healthy requires the cooperation of the larger community. Remember that some children cannot be vaccinated for documented medical reasons, and that, furthermore, vaccines don’t “take” in all children; a small percentage remains without immunity. It’s the immunity of almost all the children around these vulnerable populations that provides for their safety — that’s the concept of “herd immunity,” which posits that the immunity of a crucial percentage of people will drastically reduce the chances that a susceptible, non-immune person will be exposed to the disease.

For measles and whooping cough, the benefits of herd immunity fall to what epidemiologists consider unsafe levels when more than 8% of children are unvaccinated.


So it’s galling to read about the advice given by Dr. Robert Sears in Orange County, one of the counties that saw an outbreak of measles this year. Sears believes in the value of vaccination, according to a recent story in The Times, but tells parents that so many others are vaccinating their children that the doubters don’t have to. In other words, he’s advising them that because herd immunity works, they can exploit the parents who are doing the socially responsible thing by refusing to do the socially responsible thing themselves. “It may not be good for the public health,” he admitted to parents at a conference. “But … for your individual child, I think it is a safe enough choice.”

At the rate things are going, that could be dangerous medical advice.

Unfortunately, Sears is among the medical professionals parents can seek out under a new state law that requires them to receive information about vaccination before they can exempt their children from it. Perhaps the new law, a stronger form of which worked well in Washington state, will bring rates back up within a few years. If not, California should join the majority of states, which require vaccinations for all but religious reasons — or allow no exemptions at all.

It would help if schools were required to report their annual vaccination rates to parents, along with information about herd immunity. Parents have a right to know the dangers at their schools when immunization rates fall too low. Maybe peer pressure from alarmed parents will persuade vaccine doubters to join in what is a community, not just individual, concern.


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