Risk Factors for Invasive Pneumococcal Disease in Children in the Era of Conjugate Vaccine Use

Abstract

We conducted a case-control study to evaluate risk factors for invasive pneumococcal disease (IPD) among children who were aged 3 to 59 months in the era of pneumococcal conjugate vaccine (PCV7). IPD cases were identified through routine surveillance during 2001-2004. We matched a median of 3 control subjects to each case patient by age and zip code. We calculated odds ratios for potential risk factors for vaccine-type and non-vaccine-type IPD by using multivariable conditional logistic regression. We enrolled 782 case patients (45% vaccine-type IPD) and 2512 matched control subjects. Among children who received any PCV7, children were at increased risk for vaccine-type IPD when they had underlying illnesses, were male, or had no health care coverage. Vaccination with PCV7 did not influence the risk for non-vaccine-type IPD. Presence of underlying illnesses increased the risk for non-vaccine-type IPD, particularly among children who were not exposed to household smoking. Non-vaccine-type case patients were more likely than control subjects to attend group child care, be male, live in low-income households, or have asthma; case patients were less likely than control subjects to live in households with other children. Vaccination with PCV7 has reduced the risk for vaccine-type IPD that is associated with race and group child care attendance. Because these factors are still associated with non-vaccine-type IPD risk, additional reductions in disparities should be expected with new, higher valency conjugate vaccines.