Jane F. Seward

Recent Resurgence of Mumps in the United States

BACKGROUND The widespread use of a second dose of mumps vaccine among U.S. schoolchildren beginning in 1990 was followed by historically low reports of mumps cases. A 2010 elimination goal was established, but in 2006 the largest mumps outbreak in two decades occurred in the United States. METHODS We examined national data on mumps cases reported during 2006, detailed case data from the most highly affected states, and vaccination-coverage data from three nationwide surveys. RESULTS A total of 6584 cases of mumps were reported in 2006, with 76% occurring between March and May. There were 85 hospitalizations, but no deaths were reported; 85% of patients lived in eight contiguous midwestern states. The national incidence of mumps was 2.2 per 100,000, with the highest incidence among persons 18 to 24 years of age (an incidence 3.7 times that of all other age groups combined). In a subgroup analysis, 83% of these patients reported current college attendance. Among patients in eight highly affected states with known vaccination status, 63% overall and 84% between the ages of 18 and 24 years had received two doses of mumps vaccine. For the 12 years preceding the outbreak, national coverage of one-dose mumps vaccination among preschoolers was 89% or more nationwide and 86% or more in highly affected states. In 2006, the national two-dose coverage among adolescents was 87%, the highest in U.S. history. CONCLUSIONS Despite a high coverage rate with two doses of mumps-containing vaccine, a large mumps outbreak occurred, characterized by two-dose vaccine failure, particularly among midwestern college-age adults who probably received the second dose as schoolchildren. A more effective mumps vaccine or changes in vaccine policy may be needed to avert future outbreaks and achieve the elimination of mumps.

Updated Guidance for Palivizumab Prophylaxis Among Infants and Young Children at Increased Risk of Hospitalization for Respiratory Syncytial Virus Infection

Palivizumab was licensed in June 1998 by the Food and Drug Administration for the reduction of serious lower respiratory tract infection caused by respiratory syncytial virus (RSV) in children at increased risk of severe disease. Since that time, the American Academy of Pediatrics has updated its guidance for the use of palivizumab 4 times as additional data became available to provide a better understanding of infants and young children at greatest risk of hospitalization attributable to RSV infection. The updated recommendations in this policy statement reflect new information regarding the seasonality of RSV circulation, palivizumab pharmacokinetics, the changing incidence of bronchiolitis hospitalizations, the effect of gestational age and other risk factors on RSV hospitalization rates, the mortality of children hospitalized with RSV infection, the effect of prophylaxis on wheezing, and palivizumab-resistant RSV isolates. This policy statement updates and replaces the recommendations found in the 2012 Red Book.

Incidence of Herpes Zoster, Before and After Varicella-Vaccination-Associated Decreases in the Incidence of Varicella, 1992–2002

BACKGROUND Varicella zoster virus (VZV) causes varicella and, later in the life of the host, may reactivate to cause herpes zoster (HZ). Because it is hypothesized that exposure to varicella may boost immunity to latent VZV, the vaccination-associated decrease in varicella disease has led some to suggest that the incidence of HZ might increase. We assessed the impact that varicella vaccination has on the incidence of varicella and of HZ. METHODS Codes for cases of varicella and of HZ in an HMO were determined in automated databases of inpatients and outpatients, on the basis of the Ninth Revision of the International Classification of Diseases. We calculated the incidence, during 1992-2002, of varicella and of HZ. RESULTS The incidence of HZ remained stable as the incidence of varicella decreased. Age-adjusted and -specific annual incidence rates of varicella decreased steadily, starting with 1999. The age-adjusted rates decreased from 2.63 cases/1000 person-years during 1995 to 0.92 cases/1000 person-years during 2002; among children 1-4 years old, there was a 75% decrease between 1992-1996 and 2002. Age-adjusted and -specific annual incidence rates of HZ fluctuated slightly over time; the age-adjusted rate was highest, at 4.05 cases/1000 person-years, in 1992, and was 3.71 cases/1000 person-years in 2002. CONCLUSIONS Our findings revealed that the vaccination-associated decrease in varicella disease did not result in an increase in the incidence of HZ. These early findings will have to be confirmed as the incidence of varicella disease continues to decrease.

Varicella Mortality: Trends before Vaccine Licensure in the United States, 1970–1994

We examined varicella deaths in the United States during the 25 years before vaccine licensure and identified 2262 people who died with varicella as the underlying cause of death. From 1970 to 1994, varicella mortality declined, followed by an increase. Mortality rates were highest among children; however, adult varicella deaths more than doubled in number, proportion, and rate per million population. Despite declining fatality rates, in 1990-1994, adults had a risk 25 times greater and infants had a risk 4 times greater of dying from varicella than did children 1-4 years old, and most people who died of varicella were previously healthy. Varicella deaths are now preventable by vaccine. Investigation and reporting of all varicella deaths in the United States is needed to accurately document deaths due to varicella, to improve prevention efforts, and to evaluate the vaccines impact on mortality.

Varicella Prevention in the United States: A Review of Successes and Challenges

OBJECTIVE. In 1995, the United States was the first country to introduce a universal 1-dose childhood varicella vaccination program. In 2006, the US varicella vaccine policy was changed to a routine 2-dose childhood program, with catchup vaccination for older children. The objective of this review was to summarize the US experience with the 1-dose varicella vaccination program, present the evidence considered for the policy change, and outline future challenges of the program. METHODS. We conducted a review of publications identified by searching PubMed for the terms “varicella,” “varicella vaccine,” and “herpes zoster.” The search was limited to US publications except for herpes zoster; we reviewed all published literature on herpes zoster incidence. RESULTS. A single dose of varicella vaccine was 80% to 85% effective in preventing disease of any severity and >95% effective in preventing severe varicella and had an excellent safety profile. The vaccination program reduced disease incidence by 57% to 90%, hospitalizations by 75% to 88%, deaths by >74%, and direct inpatient and outpatient medical expenditures by 74%. The decline of cases plateaued between 2003 and 2006, and outbreaks continued to occur, even among highly vaccinated school populations. Compared with children who received 1 dose, in 1 clinical trial, 2-dose vaccine recipients developed in a larger proportion antibody titers that were more likely to protect against breakthrough disease and had a 3.3-fold lower risk for breakthrough disease and higher vaccine efficacy. Two studies showed no increase in overall herpes zoster incidence, whereas 2 others showed an increase. CONCLUSIONS. A decade of varicella prevention in the United States has resulted in a dramatic decline in disease; however, even with high vaccination coverage, the effectiveness of 1 dose of vaccine did not generate sufficient population immunity to prevent community transmission. A 2-dose varicella vaccine schedule, therefore, was recommended for children in 2006. Data are inconclusive regarding an effect of the varicella vaccination program on herpes zoster epidemiology.

The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccine coverage, 1998–2003

BackgroundThe authors sought to monitor the impact of widespread varicella vaccination on the epidemiology of varicella and herpes zoster. While varicella incidence would be expected to decrease, mathematical models predict an initial increase in herpes zoster incidence if re-exposure to varicella protects against reactivation of the varicella zoster virus.MethodsIn 1998–2003, as varicella vaccine uptake increased, incidence of varicella and herpes zoster in Massachusetts was monitored using the random-digit-dial Behavioral Risk Factor Surveillance System.ResultsBetween 1998 and 2003, varicella incidence declined from 16.5/1,000 to 3.5/1,000 (79%) overall with ≥66% decreases for all age groups except adults (27% decrease). Age-standardized estimates of overall herpes zoster occurrence increased from 2.77/1,000 to 5.25/1,000 (90%) in the period 1999–2003, and the trend in both crude and adjusted rates was highly significant (p < 0.001). Annual age-specific rates were somewhat unstable, but all increased, and the trend was significant for the 25–44 year and 65+ year age groups.ConclusionAs varicella vaccine coverage in children increased, the incidence of varicella decreased and the occurrence of herpes zoster increased. If the observed increase in herpes zoster incidence is real, widespread vaccination of children is only one of several possible explanations. Further studies are needed to understand secular trends in herpes zoster before and after use of varicella vaccine in the United States and other countries.

Varicella Vaccine Effectiveness in the US Vaccination Program: A Review

Varicella vaccine (Varivax, Merck) has been available in the United States since 1995. We reviewed published results of postlicensure studies of vaccine effectiveness. Among 19 studies, 17 reported on the effectiveness of vaccine received before exposure, and 2 reported on effectiveness after exposure. Studies used retrospective and prospective cohort, case-control, and secondary attack rate (household contact) designs. The majority of estimates assessed protection against clinically diagnosed varicella. One dose of varicella vaccine was 84.5% effective (median; range, 44%-100%) in preventing all varicella and 100% effective (mean and median) in preventing severe varicella. When administered after exposure, varicella vaccine was highly effective in preventing or modifying varicella. Although 1 dose of varicella vaccine has provided excellent protection, a higher degree of effectiveness is needed in order to interrupt transmission and to prevent outbreaks in settings with high contact rates. Monitoring the effectiveness of the newly recommended 2-dose childhood vaccine schedule for varicella vaccine is a priority.

Changing Varicella Epidemiology in Active Surveillance Sites—United States, 1995–2005

Significant reductions in varicella incidence were reported from 1995 to 2000 in the varicella active surveillance sites of Antelope Valley (AV), California, and West Philadelphia (WP), Pennsylvania. We examined incidence rates, median age, and vaccination status of case patients for 1995-2005. Coverage data were from the National Immunization Survey. By 2005, coverage among children 19-35 months of age reached 92% (AV) and 94% (WP); 57% and 64% of case patients in AV and WP, respectively, were vaccinated; and varicella incidence declined by 89.8% in AV and 90.4% in WP. Incidence declined in all age groups, especially among children <10 years of age in both sites and among adolescents 10-14 years of age in WP. In AV, since 2000, the incidence among adolescents 10-14 and 15-19 years of age increased. Implementation of school requirements through 10th grade in WP may explain the differences in the decline in incidence among adolescents. Continued surveillance will be important to monitor the impact that the 2-dose vaccine policy in children has on varicella epidemiology.

Health Care–Associated Measles Outbreak in the United States After an Importation: Challenges and Economic Impact

BACKGROUND On 12 February 2008, an infected Swiss traveler visited hospital A in Tucson, Arizona, and initiated a predominantly health care-associated measles outbreak involving 14 cases. We investigated risk factors that might have contributed to health care-associated transmission and assessed outbreak-associated hospital costs. METHODS Epidemiologic data were obtained by case interviews and review of medical records. Health care personnel (HCP) immunization records were reviewed to identify non-measles-immune HCP. Outbreak-associated costs were estimated from 2 hospitals. RESULTS Of 14 patients with confirmed cases, 7 (50%) were aged ≥ 18 years, 4 (29%) were hospitalized, 7 (50%) acquired measles in health care settings, and all (100%) were unvaccinated or had unknown vaccination status. Of the 11 patients (79%) who had accessed health care services while infectious, 1 (9%) was masked and isolated promptly after rash onset. HCP measles immunity data from 2 hospitals confirmed that 1776 (25%) of 7195 HCP lacked evidence of measles immunity. Among these HCPs, 139 (9%) of 1583 tested seronegative for measles immunoglobulin G, including 1 person who acquired measles. The 2 hospitals spent US

The incidence and clinical characteristics of herpes zoster among children and adolescents after implementation of varicella vaccination.

799,136 responding to and containing 7 cases in these facilities. CONCLUSIONS Suspecting measles as a diagnosis, instituting immediate airborne isolation, and ensuring rapidly retrievable measles immunity records for HCPs are paramount in preventing health care-associated spread and in minimizing hospital outbreak-response costs.