Host and environmental factors associated with Hib in England, 1998-2002.
BACKGROUND
Declining effectiveness of the UK's Hib vaccine programme was observed between 1998 and 2002.


OBJECTIVE
To provide insight into non-vaccine factors contributing to ongoing Hib disease in England after immunisation.


METHODS
Postal questionnaire study, matched case-control design.


METHODS
Health Protection Agency Centre for Infections, England.


METHODS
Cases were children born after 1 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.


METHODS
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 (adjusted OR (AOR) (trend) 1.51 (95% CI 1.06 to 2.13); p = 0.02) and from sole-parent households (AOR 2.56 (95% CI 1.24 to 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 (95% CI 0.99 to 8.37), p = 0.01). Day care attendance between 2 and 5 years of age was linked with a dose-dependent reduction in risk (AOR (trend) 0.79 (95% CI 0.66 to 0.93); p = 0.01), possibly because of natural boosting of immunity.


CONCLUSIONS
The association noted between invasive infection and social deprivation in this 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.
McVernon
J
J
Immunisation Department, Health Protection Agency Centre for Infections, London, UK. mcvernon@unimelb.edu.au
Andrews
N
N
Slack
M
M
Moxon
R
R
Ramsay
M
M
D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D016667:Bacterial Capsules / Q000008:administration & dosage*; D016022:Case-Control Studies; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D004739:England / Q000453:epidemiology; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000517:prevention & control; D018073:Haemophilus Vaccines / Q000008:administration & dosage*; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006801:Humans; D007223:Infant; D008297:Male; D016017:Odds Ratio; D012307:Risk Factors; D020954:Single-Parent Family; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires