San Diego measles outbreak highlights consequences of intentional undervaccination

Issue: April 2010

High vaccine exemption rates at charter and private schools in a San Diego community contributed to the largest measles outbreak in the area since 1991, study findings suggested.

The outbreak ensued when an intentionally unvaccinated 7-year-old boy returned from Switzerland and unknowingly imported the disease. From Jan. 11 to Feb. 29, 2008, an additional 839 people were exposed and 11 additional measles cases were identified, all in unvaccinated children, the researchers reported. One measles-related hospitalization occurred in an infant too young to be vaccinated, and an additional 48 children too young to be vaccinated were quarantined.

Two-dose measles vaccination coverage among kindergarteners was high at 95% throughout the county, but a “vigorous outbreak response was still necessary to halt the spread of the disease beyond a third generation,” according to the researchers. They estimated the cost of containing the outbreak at $775 per child per family and the net public-sector cost at $10,376 per case.

“The outbreak was fueled by clusters of intentionally unvaccinated children and perpetuated by delayed clinical diagnosis and inadequate infection control measures,” the researchers wrote, noting that measles is highly contagious and delayed recognition common since the disease is nearly eliminated in the United States.

“[I]f intentional undervaccination rates continue to rise, measles could again become an endemic disease, as has happened recently in the United Kingdom.”

Overall vaccine exemption rates were 2.5% among San Diego kindergartners; however, data indicate that rates were significantly higher among children who attended 34 public charter schools (11%; n=204 of 1,870) and 208 private schools (5%; n=181 of 3,857) vs. those who attended 404 general public schools (1.8%; n=587 of 33,405).

The researchers noted particularly high exemption rates in a group of four contiguous school districts (9%; n=168 of 1,862; P<.001)) and a single charter school (30%; n=12 of 40) compared with the rest of the county (2.2%; n=804 of 37, 270).

Results from surveys and discussion groups revealed that San Diego parents who chose not to vaccinate their children were most commonly non-Hispanic white (91% vs. 50%), college-educated (91% vs. 34%) and had household incomes higher than $100,000 (51% vs. 19%) compared with the overall county population.

The researchers determined that the parents of intentionally unvaccinated children were often skeptical of the government, pharmaceutical industry and medical community, were likely to believe that a ‘natural lifestyle’ was sufficient to protect children from vaccine-preventable diseases, and that vaccines can cause “multiple health conditions, especially autism.”

The researchers noted that 41% of parents who had previously declined vaccination for their children accepted the vaccine during the outbreak. – by Nicole Blazek

Sugarman DE. Pediatrics. 2010;125:747-755.

The San Diego measles outbreak in 2008 once again shows the importance of herd immunity. For highly contagious viruses, like measles, about 95 percent of the population needs to be immunized to effectively prevent spread.

At the center of the epidemic was a child whose parents had chosen not to vaccinate him. He proceeded to infect many with whom he came in contact, including several children in the pediatrician's office who were too young to be have received MMR. The mother hadn't made a choice for her son only, but for everyone with whom he'd come in contact.

Is it reasonable that this mother's rights should include the right to have her child catch and transmit a potentially fatal infection?

– Paul Offit, MD
Infectious Diseases in Children Editorial Board

I hate to say I told you so, like your momma does, but I told you so. Measles is so ridiculously easy to prevent, yet the MMR vaccine is vilified on the Internet. In this article, I know people from the CDC and the AAP and your local pediatrician seem to be allegedly conspiring against the rich and upper class, but take my word for it, we are more like the LAPD. "To serve and to protect" is our primary goal for all children. The paranoia and over-thinking about vaccines by these non-vaccinating folks is astonishing.

Once again these data show that it is imperative for schools to post their full vaccination rates for each grade, in full disclosure, for other attendees. Pediatricians must also take proactive precautions with the growing number of unvaccinated, potentially biohazardous children and immediately place them in an examination room away from office traffic flow. It is totally unfair to expose the rest of your patients who are trying their best to protect their children with recommended vaccines. The risk of vaccine-preventable brain damage, death and other morbidities are well-known to all pediatricians. If these precautions are not taken, one day the medico-legal implications may come back to haunt these parents.

– Stan Block, MD
Infectious Diseases in Children Editorial Board

Follow the PediatricSuperSite.com on Twitter.