Changing epidemiology of outpatient bacteremia in 3- to 36-month-old children after the introduction of the heptavalent-conjugated pneumococcal vaccine.

BACKGROUND: The introduction of routine vaccination with heptavalent conjugated pneumococcal vaccine has changed the overall incidence of bacteremia in children 3 months-3 years old. OBJECTIVE: To describe the changing incidence and etiology of bacteremia in previously healthy toddlers presenting to outpatient clinical settings. METHODS: Retrospective case series of all blood cultures obtained between September 1998 and August 2003 in Kaiser Permanente Northern California outpatient clinics and emergency departments from previously healthy children 3 months-3 years old. RESULTS: Implementation of routine vaccination with the conjugated pneumococcal vaccine resulted in an 84% reduction of Streptococcus pneumoniae bacteremia (1.3-0.2%) and a 67% reduction in overall bacteremia (1.6-0.7%) in the study population. The rate of blood culture isolation of contaminating organisms remained unchanged at 1.8%; therefore, by the end of the study, >70% of organisms identified in blood cultures were contaminants. During the 5 study years, total blood cultures drawn decreased by 35% in outpatient pediatric clinics but remained unchanged in emergency departments. By 2003, one-third of all pathogenic organisms isolated from blood cultures were Escherichia coli, one-third were non-vaccine serotype S. pneumoniae, the majority of the remaining one-third were Staphylococcus aureus, Salmonella spp., Neisseria meningitidis and Streptococcus pyogenes. In our population of children routinely immunized with the conjugated pneumococcal vaccine, a white blood cell count >15,000 by itself is a poor predictor of bacteremia in the febrile toddler (sensitivity, 74.0%; specificity, 54.5%; positive predictive value, 1.5%; negative predictive value, 99.5%). CONCLUSION: In the United States, routine vaccinations with Haemophilus influenzae type b and S. pneumoniae vaccines have made bacteremia in the previously healthy toddler a rare event. As the incidence of pneumococcal bacteremia has decreased, E. coli, Salmonella spp. and Staphylococcus aureus have increased in relative importance. The use of the white blood cell count alone to guide the empiric use of antibiotics is not indicated. New guidelines are needed to approach the previously healthy febrile toddler in the outpatient setting.

Impact of maternal influenza vaccination during pregnancy on the incidence of acute respiratory illness visits among infants.

OBJECTIVE: To determine whether influenza vaccination of pregnant women prevents visits for respiratory illness in their infants born during the influenza season. DESIGN: Retrospective matched cohort study. SETTING: Four managed care organizations in the United States. Patients A total of 41 129 infants (3160 and 37 969 born to vaccinated and unvaccinated mothers, respectively) born between 1995 and 2001. Main Exposure Maternal influenza vaccination. Infants were considered exposed if their gestational age at birth was at least 30 weeks, if the time from maternal vaccination to birth was at least 28 days, and if they were exposed to at least 14 days of the influenza season. MAIN OUTCOME MEASURES: Incidence of acute respiratory illnesses (outpatient, emergency department, and inpatient settings combined) and incident rate ratios (IRRs) for infants exposed and unexposed to maternal vaccination during the following 4 periods: peak influenza, respiratory syncytial virus predominant, periseasonal, and summer weeks. The time to the first acute respiratory illness during peak influenza weeks was also assessed. RESULTS: During the peak influenza weeks, infant visit rates were 15.4 and 17.1 per 100 person-months for exposed and unexposed infants, respectively (IRR, 0.90; 95% confidence interval, 0.80-1.02). Adjusted IRRs for the 4 periods found a protective effect of infant female sex, whereas Medicaid status and maternal high-risk status increased infant visit rates. Maternal influenza vaccination did not reduce visit rates during any of the 4 time periods (IRR for peak influenza season, 0.96; 95% confidence interval, 0.86-1.07) and did not delay the onset of first respiratory illness. CONCLUSION: We were unable to demonstrate that maternal influenza vaccination reduces respiratory illness visit rates among their infants.

Risk of immune thrombocytopenic purpura after measles-mumps-rubella immunization in children.

BACKGROUND: The measles-mumps-rubella vaccine has been associated with immune thrombocytopenia purpura in 2 small studies. METHODS: By using the Vaccine Safety Datalink, we identified measles-mumps-rubella-vaccinated children aged 1 to 18. A case of immune thrombocytopenia purpura was defined as a patient with a platelet count of < or = 50,000/microL with clinical bleeding and normal red and white blood cell indices. The immune thrombocytopenia purpura incidence rates during exposed (42 days after vaccination) and unexposed time periods were determined. A retrospective cohort of vaccinated children was used to determine incident rate ratios for children aged 1 to 18 years, 12 to 23 months, and 12 to 15 months. RESULTS: A total of 1,036,689 children received 1,107,814 measles-mumps-rubella vaccinations; there were 259 confirmed patients with immune thrombocytopenia purpura. Because only 5 exposed cases occurred after age 2, analyses were limited to children aged 12 to 23 months. Exposed patients aged 12 to 23 months had lower median platelet counts than those who were unexposed and had similar median duration of illness (11 vs 10 days). The incident rate ratio was highest for children aged 12 to 15 months at 7.10. The incident rate ratio for boys aged 12 to 15 months was 14.59, and the incident rate ratio for girls in the same age group was 3.22. Seventy-six percent of immune thrombocytopenia purpura cases in children aged 12 to 23 months were attributable to measles-mumps-rubella vaccination. This vaccine causes 1 case of immune thrombocytopenia purpura per every 40,000 doses. CONCLUSION: Measles-mumps-rubella vaccine that is given in the second year of life is associated with an increased risk of immune thrombocytopenia purpura.