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Friday, September 7, 2018

Unvaccinated Clusters Persist Despite CA Vax Law

In The Politics of Autism, I look at the discredited notion that vaccines cause autism.

Laura Santhanam at PBS NewsHour:
A California law that aims to limit the number of people who can refuse vaccines has led to a slight improvement in kindergartners’ vaccination rate in recent years, according to a new study in Health Affairs. But the law was not as effective in private schools, and did little to break up localized clusters of children who opted out of vaccines.
It’s these local clusters of vaccinations that put a specific community or school at the greatest risk, according to the study, which linked large measles outbreaks across the United States to “declining population vaccination and to voluntary abstention from measles vaccine.”
“All disease transmission is local, just like politics,” said Saad Omer, a professor in global health and epidemiology at Emory University in Atlanta and one of the study authors. He added that national and state monitoring is not enough to effectively monitor infectious disease; more needs to be done on the local and county level.
In a now-retracted 1998 study published in the journal the Lancet, Dr. Andrew Wakefield claimed a false link between autism and the vaccine for measles, mumps and rubella. This study has been widely and repeatedly debunked. But some people continue to point to it as justification for avoiding immunization.
At Health Affairs, Malia Jones and colleagues have an article titled "Mandatory Health Care Provider Counseling For Parents Led To A Decline In Vaccine Exemptions In California." The abstract:
Receipt of childhood vaccinations in the US has been declining, and outbreaks of preventable infectious diseases have become more common. In response, in 2014 California implemented a policy change for exemptions from mandatory vaccines for school enrollment. Data on fifteen successive cohorts of kindergarteners enrolled in public and private schools between school years 2001–02 and 2015–16 were analyzed for changes in vaccination trends. The results show an increase in the prevalence and clustering of vaccine exemptions from 2001–02 through 2013–14, followed by a modest decline after implementation of a policy mandating health care provider counseling for vaccine exemption. Clustering of vaccine exemptions increased over the study period and was less responsive to the policy change than were exemption rates overall. Nor did the policy change uniformly reduce the clustering of at-risk students across counties. Trends in the use of conditional admission showed strong school-level clustering and remained relatively stable. The policy change was effective at reducing exemption rates but did not uniformly reduce clustering of exemptions. The results suggest the need to evaluate the causes of local-area clustering and to adopt a statewide policy that addresses clustering of vaccine exemptions within schools and counties.