Jessica E. Atwell, Josh Van Otterloo, Jennifer Zipprich, Kathleen Winter, Kathleen Harriman, Daniel A. Salmon, Neal A. Halsey and Saad B. Omer Pediatrics; originally published online September 30, 2013;
DOI: 10.1542/peds.2013-0878
The online version of this article, along with updated information and services, is located on the World Wide Web at: http://pediatrics.aappublications.org/content/early/2013/09/24/peds.2013-0878
WHAT’S KNOWN ON THIS SUBJECT: Previous studies have shown that nonmedical exemptions (NMEs) to immunization cluster geographically and contribute to outbreaks of vaccine- preventable diseases such as pertussis. The 2010 pertussis resurgence in California has been widely attributed to waning immunity from acellular pertussis vaccines.
WHAT THIS STUDY ADDS: This study provides evidence of spatial and temporal clustering of NMEs and clustering of pertussis cases and suggests that geographic areas with high NME rates were also associated with high rates of pertussis in California in 2010.
BACKGROUND: In 2010, 9120 cases of pertussis were reported in California, more than any year since 1947. Although this resurgence has been widely attributed to waning immunity of the acellular vac- cine, the role of vaccine refusal has not been explored in the pub- lished literature. Many factors likely contributed to the outbreak, including the cyclical nature of pertussis, improved diagnosis, and waning immunity; however, it is important to understand if clustering of unvaccinated individuals also played a role.
METHODS: We analyzed nonmedical exemptions (NMEs) for children entering kindergarten from 2005 through 2010 and pertussis cases with onset in 2010 in California to determine if NMEs increased in that period, if children obtaining NMEs clustered spatially, if pertussis cases clustered spatially and temporally, and if there was statistically signif- icant overlap between clusters of NMEs and cases.
RESULTS: Kulldorff’s scan statistics identified 39 statistically significant clusters of high NME rates and 2 statistically significant clusters of pertussis cases in this time period. Census tracts within an exemptions cluster were 2.5 times more likely to be in a pertussis cluster (odds ratio = 2.47, 95% confidence interval: 2.22–2.75). More cases occurred within as compared with outside exemptions clusters (incident rate ratios = 1.20, 95% confidence interval: 1.10–1.30). The association remained significant after adjustment for demographic factors. NMEs clustered spatially and were associated with clusters of pertussis cases.
CONCLUSIONS: Our data suggest clustering of NMEs may have been 1 of several factors in the 2010 California pertussis resurgence. Pediatrics 2013;132:624–630
But seems to me like a lot of work here is trying to show that NMEs caused the disease outbreak.
Look at this figure from the article:
What on earth does this show? Looks like no association or maybe a random association.
And overall, they found 41 clusters of NMEs, and then describe two 2 clusters that had higher than expected pertussis. Except these last two clusters weren't described in the NME clusters.
Then they write:
Census tracts within a NME cluster were more likely to be in a pertussis case cluster than census tracts outside of a NME cluster (OR = 2.47, 95% CI: 2.22– 2.75). The association between the overlap remained significant after adjustment for proportion of racial/ ethnic minorities, population density, average family size, proportion of the population with a college degree, metropolitan area designation, and median household income (OR = 1.73, 95% CI: 1.53–1.96).
The incidence of pertussis was higher within NME clusters than outside of NME clusters (IRR = 1.20, 95% CI: 1.10–1.30). The association remained significant after adjustment for demographic factors (IRR = 1.12, 95% CI: 1.02–1.23).
But where is the actual data for this? Why don't they show these numbers instead of the weird, poorly described data tables and meaningless figure (above) they do show?
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