Tuesday, March 23rd, 2010


A pediatrician friend of mine pointed out this bit of news in Pediatrics on the January 2008 outbreak of measles in San Diego:

The outbreak began in January 2008 when a 7-year-old boy whose parents refused to vaccinate him returned to the U.S. from Switzerland. Before symptoms appeared, he infected his 3-year-old brother and 9-year-old sister. Neither was vaccinated.

Neither were 11% of the boy’s classmates, whose parents shared similar beliefs that a healthy lifestyle protected against disease while vaccines were riskier than the illnesses they prevented.

In the end, 839 people were exposed to measles. Eleven were infected, and 48 exposed kids too young to be vaccinated were quarantined — forbidden to leave their homes — for 21 days. Jane Seward, MBBS, MPH, was the CDC’s senior investigator for the outbreak.

Despite the extraordinary efforts of health workers, what really ended the San Diego outbreak wasn’t quarantine or post-exposure vaccination. It was the high vaccination rate in the rest of the community that kept the outbreak from becoming an epidemic.

This is the summary of the study:

The importation resulted in 839 exposed persons, 11 additional cases (all in unvaccinated children), and the hospitalization of an infant too young to be vaccinated. Two-dose vaccination coverage of 95%, absence of vaccine failure, and a vigorous outbreak response halted spread beyond the third generation, at a net public-sector cost of $10376 per case. Although 75% of the cases were of persons who were intentionally unvaccinated, 48 children too young to be vaccinated were quarantined, at an average family cost of $775 per child. Substantial rates of intentional undervaccination occurred in public charter and private schools, as well as public schools in upper-socioeconomic areas. Vaccine refusal clustered geographically and the overall rate seemed to be rising. In discussion groups and survey responses, the majority of parents who declined vaccination for their children were concerned with vaccine adverse events.

CONCLUSIONS Despite high community vaccination coverage, measles outbreaks can occur among clusters of intentionally undervaccinated children, at major cost to public health agencies, medical systems, and families. Rising rates of intentional undervaccination can undermine measles elimination.

The medical and public health community needs to really get going on this. The article ends by saying the researchers met parents with “real fears” about the risk of autism from vaccines. I’m sure their fears are real, but how on earth do you convince them otherwise?

In case you’re at USC or in the area, I’m giving a talk tomorrow there on some of the work I’ve been doing with Kamalika Chaudhuri (whose website seems to have moved) and Claire Monteleoni on privacy-preserving machine learning.

Learning from sensitive data – balancing accuracy and privacy

Wednesday, March 24th, 2010
2:00pm-3:00pm
EEB 248

The advent of electronic databases has made it possible to perform data mining and statistical analyses of populations with applications from public health to infrastructure planning. However, the analysis of individuals’ data, even for aggregate statistics, raises questions of privacy which in turn require formal mathematical analysis. A recent measure called differential privacy provides a rigorous statistical privacy guarantee to every individual in the database. We develop privacy-preserving support vector machines (SVMs) that give an improved tradeoff between misclassification error and the privacy level. Our techniques are an application of a more general method for ensuring privacy in convex optimization problems.

Joint work with Kamalika Chaudhuri (UCSD) and Claire Monteleoni (Columbia)

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