Karin Galil

Reemergence of invasive Haemophilus influenzae type b disease in a well-vaccinated population in remote Alaska.

Before vaccination, Alaska Natives experienced very high rates of invasive Haemophilus influenzae type b (Hib) disease and carriage. Vaccination with Hib conjugate vaccine PRP-OMP (polyribosylribitol phosphate Neisseria meningitidis outer membrane protein) began in 1991 and resulted in a sharp decline in cases. In 1996, after switching to a different Hib conjugate vaccine, DTP-HbOC (which combines diphtheria-tetanus-whole cell pertussis vaccines with HbOC [Hib oligosaccharide CRM197]), cases of invasive Hib disease increased, suggesting ongoing Hib transmission despite widespread vaccination. To determine the prevalence of and risk factors for carriage, a cross-sectional study of oropharyngeal Hib carriage was conducted among Alaska Native children aged 1-5 years in remote southwestern Alaska. Of 496 children with swabs taken, 46 (9.3%) were colonized with Hib. Carriage rates varied by village from 2.2% to 13.2% and by age from 6.1% in 1-year-olds to 14.7% in 5-year-olds. Crowding was associated with Hib carriage. Widespread vaccination with PRP-OMP Hib conjugate vaccine did not eliminate carriage in this population of Alaska Natives, and ongoing carriage contributed to disease resurgence.

Younger Age at Vaccination May Increase Risk of Varicella Vaccine Failure

To determine vaccine effectiveness (VE), a varicella outbreak in a highly vaccinated day-care center (DCC) population in Pennsylvania was investigated. In Pennsylvania, proof of immunity is required for children >or=12 months old for DCC enrollment. Questionnaires were administered to parents of children who had attended the DCC continuously during the study period (1 November 1999-9 April 2000) to determine history of varicella disease or vaccination and for information about any recent rash illnesses. VE was calculated for children >or=12 months old without a history of varicella. There were 41 cases of varicella among 131 attendees, with 14 cases (34%) among vaccinated children. VE was 79% against all varicella and 95% against moderate or severe varicella. Vaccination at <14 months was associated with an increased risk of breakthrough disease (relative risk, 3.0; 95% confidence interval, 0.9-9.9). Despite varicella vaccination coverage of 80%, a sizeable outbreak occurred. Early age at vaccination may increase the risk of vaccine failure.

Epidemiology of Varicella Hospitalizations in the United States, 1995–2005

To describe the impact of the varicella vaccination program on varicella-related hospitalizations (VRHs) in the United States, data from the Varicella Active Surveillance Project (VASP) were used to compare rates of hospitalization and rates of complications among patients hospitalized for varicella-related conditions from 1995 to 2005. Of the 26,290 varicella cases reported between 1995 and 2005, 170 cases resulted in VRHs, including 1 case that resulted in death. Both VRH rates per 100,000 population and complications during VRH per 100,000 population decreased significantly between the early vaccination period (1995-1998) and the middle/late vaccination period (1999-2005). Infants and adults were at highest risk for VRH, and having been vaccinated against varicella was a protective factor. Varicella vaccination may have prevented a significant number of VRHs. The fact that 4 vaccinated children required hospitalization for varicella-related complications demonstrates that 1 dose of varicella vaccine does not prevent serious disease in all cases, even among previously healthy children.

Postpartum varicella vaccination: is the vaccine virus excreted in breast milk?

OBJECTIVE To evaluate whether the varicella vaccine virus is detected in breast milk after vaccination of breast-feeding women and whether there is serologic evidence of exposure of the infant to varicella virus after maternal vaccination. METHODS We enrolled women identified as varicella seronegative during routine prenatal screening at Group Health Cooperative. Participants received the first dose of varicella vaccine at least 6 weeks postpartum and the second dose at least 4 weeks later. They collected ten breast milk samples after each vaccine dose. Breast milk samples were tested for varicella-zoster virus by polymerase chain reaction (PCR). Serum specimens were collected from the mothers 1 month after each vaccine dose, and peripheral blood from their infants was collected onto filter spots 1 month after the mothers second dose. These samples were tested for varicella immunoglobulin (Ig) G by whole-virus enzyme-linked immunosorbent assay (ELISA), or by the more sensitive glycoprotein ELISA. When possible, filter spots from the infants were also tested by PCR for the presence of varicella zoster virus deoxyribonucleic acid (DNA). RESULTS Twelve women were enrolled; all seroconverted after the first vaccine dose. Varicella DNA was not detected by PCR in any of the 217 postvaccination breast milk specimens. None of the infants was seropositive. Samples from six infants were tested for varicella zoster virus DNA by PCR, and all were negative. CONCLUSION We found no evidence of varicella vaccine virus excretion in breast milk. These findings suggest that postpartum vaccination of varicella-susceptible women need not be delayed because of breast-feeding.

The Use of School-Based Vaccination Clinics to Control Varicella Outbreaks in Two Schools

School-based vaccination clinics were offered in 2 schools experiencing varicella outbreaks. The clinics raised coverage of susceptible children from 52.9% to 92.2% and from 68.8% to 85.3% in the 2 schools, respectively. Although routine immunization and school-entry requirements are the best strategies for preventing outbreaks, school-based vaccination clinics may greatly increase coverage and shorten outbreaks.

Tracking Varicella Deaths: Accuracy and Completeness of Death Certificates and Hospital Discharge Records, New York State, 1989–1995

Before widespread vaccination, varicella infection resulted in more than 11 000 hospitalizations1 and 100 deaths annually in the United States.2 Since vaccine licensure in 1995, varicella incidence has decreased markedly.3 Mathematical models have predicted that vaccination will shift the peak incidence of disease to older ages as the incidence declines.4 Because older persons are at increased risk of morbidity and mortality from varicella,5,6 it is essential to monitor these outcomes as vaccination coverage increases.7,8 The Centers for Disease Control and Prevention (CDC) encourages state health departments to search death certificates and hospital discharge databases to estimate the number of varicella deaths. In this study, we assessed the validity and utility of these data sources.