Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 132 (4), 624-30

Nonmedical Vaccine Exemptions and Pertussis in California, 2010

Affiliations

Nonmedical Vaccine Exemptions and Pertussis in California, 2010

Jessica E Atwell et al. Pediatrics.

Abstract

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 vaccine, the role of vaccine refusal has not been explored in the published 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 significant 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.

Keywords: California; cluster analysis; immunization; nonmedical vaccine exemptions; pertussis; vaccine refusal.

Similar articles

See all similar articles

Cited by 48 PubMed Central articles

See all "Cited by" articles

Publication types

Substances

LinkOut - more resources

Feedback