High Rates of Vaccine Refusal Linked to 2010 Calif. Pertussis Epidemic
A new study published in the journal Pediatrics that looked at the 2010 outbreak of pertussis, or whooping cough, in California found that areas with high rates of individuals refusing vaccines were more likely to see increased cases of the disease, USA Today reports (Healy, USA Today, 9/30).
In 2010, California had a record-breaking whooping cough epidemic. There were more than 9,100 reported cases of pertussis and 10 infant deaths stemming from the illness that year, marking 2010 as the worst year for whooping cough in the state since 1947.
As a result, state law now requires students entering grades seven through 12 to receive a whooping cough booster shot within 30 days of starting school, unless they submit a personal belief exemption (California Healthline, 7/20/12). Parents can obtain an exemption for their children if immunizations are against their religious or philosophical beliefs.
Details of Study
Researchers examined data from the California Department of Public Health on non-medical exemptions obtained for kindergarten children from 2005 to 2010. They also analyzed pertussis cases in the state diagnosed in 2010.
The study found:
- 39 "geographical clusters" that had high rates of nonmedical exemptions; and
- Two statistically significant clusters of pertussis diagnoses.
Districts within one of the 39 areas with high numbers of exemptions were 2.5 times more likely to also be in a cluster of pertussis diagnoses.
Both clusters were linked to characteristics of higher socioeconomic status, including:
- Lower population density;
- Smaller family size;
- Lower percentage of racial or ethnic minorities; and
- Higher median household income.
The authors concluded that large populations of individuals being intentionally unvaccinated or undervaccinated can lead to an outbreak of pertussis (USA Today, 9/30).This is part of the California Healthline Daily Edition, a summary of health policy coverage from major news organizations. Sign up for an email subscription.