Objective: Declining effectiveness of the UK's Hib vaccine programme was observed between 1998 and 2002. This study sought to provide insight into non-vaccine factors contributing to ongoing Hib disease in England following immunisation.
Design: Postal questionnaire study, matched case-control design.
Setting: Health Protection Agency Centre for Infections, England.
Patients: Cases were children born after 1st January 1993 presenting with confirmed Hib infection in England between the start of 1998 and end of 2002, regardless of vaccination status. Controls were matched by date of birth and region.
Main outcome measures: Odds ratios were calculated to assess the impact of host and environmental variables on disease risk.
Results: Increased disease risk was noted among children with frequent antibiotic use [AOR (trend) 1.51 (95% CI 1.06, 2.13); p=0.02) and from sole parent households [AOR 2.56 (95%CI 1.24, 5.29); p=0.01]. These two risk factors were further related to each other, consistent with previously reported associations between infection and social deprivation. In fully immunised children, receipt of all three doses of the primary course as an acellular pertussis containing combination vaccine (DTaP-Hib) increased the risk of vaccine failure [OR 2.88 (0.99, 8.37), p=0.01]. Day care attendance between two and five years of age was linked with a dose dependent reduction in risk [AOR (trend) 0.79 (0.66, 0.93); p=0.01], possibly due to natural boosting of immunity.
Conclusions: The association noted between invasive infection and social deprivation in our own and other studies is concerning, and merits further investigation. The importance of ongoing surveillance of vaccine preventable diseases to allow nested studies of this kind was reinforced.
- child day care centers
- epidemiologic studies
- haemophilus influenzae
- socioeconomic factors