Herd Immunity from Meningococcal Serogroup C Conjugate Vaccination.

Overall, children looked after by local authorities were more than twice as likely to not receive meningococcal C vaccine than children at home (risk ratio 2.17 adjusting for age and district, 95% confidence interval 2.06 to 2.28, Mantel-Haenszel method). Because universal childhood meningococcal C vaccination was introduced recently, we were able to study the effectiveness of public care without bias from historical health neglect. Although sampling was opportunistic, our findings are likely to be generalisable as immunisation indices for children in public care in the districts surveyed all fell within one standard deviation of the national mean. We did not examine the reasons for failure to immunise. However, during 2001, 16% of children in public care moved placement more than three times. This instability creates potent risk factors, including missed school based immunisation and discontinuity of primary care. The reversed risk ratio for young children in some districts may reflect greater stability in their placements, primary care organisation of the preschool campaign, or targeting of vulnerable children by health visitors. We suggest two ways forward. Firstly, health services should be made accountable for immunisation uptake as well as social services. Secondly, effective shared information systems between health and social services need to be introduced. Together these measures would better protect our most vulnerable children from disease.