Wednesday, August 3, 2011 | Orange County residents are vaccinating their children less, with the proportion of fully vaccinated kindergarteners slipping from 93 percent in the mid 2000s to 89 percent in 2010.

Vaccine compliance rates are lowest in Laguna Beach Unified and Capistrano Unified school districts, both less than 85 percent. County health agency officials and others say the drop perhaps reflects the higher prevalence of vaccine fears among wealthier populations.

These two districts also had the highest percentage of vaccine exemptions based on personal belief. Meanwhile, Anaheim City, La Habra City and Garden Grove Unified school districts are at vaccination rates of 95 percent or above.

“It does tend to be that the more affluent, white, more educated populations are more likely to refuse vaccinations,” said Dr. David Nunez, family health medical director of the Orange County Health Care Agency.

Public health officials fear that the drop could pull Orange County below the “herd immunity” threshold, the percentage of immunized people in a population needed to prevent an outbreak.

Such an outbreak could occur in several groups: among children 2 and younger who have not yet been vaccinated; among those not vaccinated; and even among those vaccinated, since vaccines are not always effective. The health of developing fetuses is also at risk if pregnant women contract communicable illnesses.

The under-immunized — a growing percentage of children entering school with some but not all vaccinations — are similarly subject to an outbreak, said Nunez. Last June saw a spike in pertussis (whooping cough), with 338 cases in Orange County, most among infants. Five pertussis vaccinations are required by age five, and California students in grades 7-12 are now required to get a booster.

“One of our biggest fears is we have these pockets of under-immunized children at risk for having outbreaks in communities. We need a certain level of vaccine coverage in a community in order to stop an outbreak of a communicable disease,” Nunez said.

Nunez said the reasons for immunization decline are mixed. Lower-income, more transient populations don’t always get regular medical care and can fall between the cracks. Some parents are delaying vaccines or selecting only some, and others are simply complacent, assuming vaccines have eliminated the threat of outbreak.

Still other parents are declining to vaccinate due to fears that vaccines lead to autism. The anti-vaccine movement is highly active, especially on the Internet, and has gained significant media attention, Nunez said.

But he echoed leading health authorities, including the Centers for Disease Control and Prevention, in saying there is no evidence connecting vaccines to autism. A highly cited medical journal article that claimed a link was recently debunked.

Nunez wants to do more to counter anti-vaccination claims by improving his agency’s website and using Facebook and Twitter. He said it’s important to respect parents’ concerns about vaccines.

“People have honest questions about vaccine safety and side effects, and we need to make information available,” Nunez said.

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