In the Journals

States with higher pertussis rates may be related to nonmedical exemptions from school vaccinations

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January 19, 2014

Annual reported rates of pertussis may be linked to state laws governing nonmedical exemptions for mandatory vaccines in schoolchildren, according to recent study findings.

The longitudinal study hypothesized that the incidence rates of vaccine-targeted diseases (VTDs) in children of individual states are directly correlated with the use of nonmedical exemptions (NME) in those states.

Because direct measurements of state NME use were not available, the researchers utilized state NME restrictiveness levels and vaccine-specific uptake levels as proxies for this variable. State uptake rates for a given vaccine was quantified as the percentage of children aged 36 months who have received all CDC-recommended doses of that vaccine. Vaccine uptake data were collected from the CDC’s annual National Immunization Survey for 2000 to 2008.

State-level incidence rates from 2001 to 2008 were gathered for five VTDs: measles, mumps, pertussis, Haemophilus influenzae type b and hepatitis B. The diseases were chosen because they are reported with sufficient frequency to the CDC to permit mixed-effects models. State-level VTD rates were calculated by dividing the number of CDC-reported cases from each state for individuals aged 18 years and younger by the state population estimates from the US Census Bureau’s Population Estimates for the same age group. Multivariate regression analysis was used to determine the relationship between the VTDs and the state NME restrictiveness.

The study researchers reported that the rates for hepatitis B (P=.81), Hib (P=.36), measles (P=.34) and mumps (P=.21) were not related to state NME law restrictiveness. However, more restrictive state NME laws were significantly and inversely associated with pertussis incidence rates (P=.03).

“Pertussis remains a significant public health problem and source of morbidity and mortality among both vaccinated and unvaccinated persons, especially infants too young to be fully vaccinated,” the researchers wrote. “Thus, policymakers must balance multiple competing requests to not only strengthen public health infrastructures and protect the well-being of populations, but also safeguard the self-determination rights of individuals who choose not to take potentially ineffective medical treatments that can cause serious temporary and permanent adverse events.”

Disclosure: This research was funded by the Robert Wood Johnson Foundation’s Public Health Law Research Program.