Oral polio vaccine and intussusception: a data linkage study using records for vaccination and hospitalization.

The authors investigated the possibility of an association between oral polio vaccine (OPV) and intussusception by linking Scottish vaccination and hospitalization data sets and performing self-controlled case series analysis. The issue was important because rotavirus vaccine, another live oral virus vaccine, was withdrawn from the market in 1999 after studies showed a strong association with intussusception. OPV was recommended for all infants in the United Kingdom at ages 2, 3, and 4 months until 2004, when new combination vaccines containing inactivated poliovirus were introduced. Analysis was carried out for 466 intussusception cases occurring in 1987-1999 for which linked records on OPV vaccination were available. Six possible risk periods for intussusception, ranging from 3 days after vaccination to 41 days after vaccination, were examined, with separate analysis for each of the three OPV doses and also for data on all three doses combined. Of the 24 possible risk periods examined, the relative incidence of intussusception after vaccination was unchanged for 18, significantly decreased for five, and significantly increased for only one. The authors conclude that overall, there is no evidence for an association between OPV and intussusception, even when each dose is considered separately.

Thyroid disease and increased cardiovascular risk.

The effects of thyroid dysfunction are thought to be reversible on restoration of euthyroidism, but postmortem and epidemiologic data suggest that subclinical or treated thyroid disease is associated with increased vascular risk. In order to determine the extent of this risk, and to explore whether the nature and/or treatment of thyroid disease are critical in this relationship, we used medical record linkage to match patients with treated thyroid disease of various etiologies with routinely collected national inpatient and daycase hospital discharge records and death records, and assessed the number of hospitalizations from cardiovascular or cerebrovascular disease or death in patients with thyroid disease and control patients. Patients treated for Graves' disease had more hospitalizations from cardiovascular disease than controls (relative risk, 1.42; 95% confidence interval, 1.20 to 1.67; p < 0.001). Toxic multinodular goiter was also associated with significantly higher rates of cardiovascular disease (relative risk, 1.50; 95% confidence interval, 1.11 to 2.02; p = 0.008). Patients with Hashimoto's thyroiditis aged over 50 years had a threefold increase in cardiovascular admissions compared to controls (23.5% and 6.5%, respectively; 95% confidence interval for difference, 6.0% to 27.9%; p = 0.003). Thus, different forms of thyroid disease were associated with increased long-term vascular risk despite restoration of euthyroidism. The mechanisms that mediate this risk are unclear but may not involve thyroid hormone abnormality.