Varicella Vaccination Coverage among Adolescents Ages 13–17 Years, United States, National Immunization Survey, 2007–2014 (original) (raw)

Impact of vaccination on the epidemiology of varicella: 1995-2009

Pediatrics, 2014

When varicella vaccine was licensed in the United States in 1995, there were concerns that childhood vaccination might increase the number of adolescents susceptible to varicella and shift disease toward older age groups where it can be more severe. We conducted a series of 5 cross-sectional studies in 1994 to 1995 (prevaccine), 2000, 2003, 2006, and 2009 in Kaiser Permanente of Northern California to assess changes in varicella epidemiology in children and adolescents, as well as changes in varicella hospitalization in people of all ages. For each study, information on varicella history and varicella occurrence during the past year was obtained by telephone survey from a sample of ∼8000 members 5 to 19 years old; varicella hospitalization rates were calculated for the entire membership. Between 1995 and 2009, the overall incidence of varicella in 5- to 19-year-olds decreased from 25.8 to 1.3 per 1000 person-years, a ∼90% to 95% decline in the various age categories (5-9, 10-14, and...

Impact of Vaccination on the Epidemiology of Varicella

WHAT'S KNOWN ON THIS SUBJECT: Varicella vaccine is effective, but there is concern that widespread use in young children may lead to a shift in the age of infection, with potentially more severe disease later in childhood and adolescence. WHAT THIS STUDY ADDS: This study documents that varicella vaccine resulted in a decline of varicella incidence and hospitalization in all age groups, with no shift to older age groups. abstract BACKGROUND: When varicella vaccine was licensed in the United States in 1995, there were concerns that childhood vaccination might increase the number of adolescents susceptible to varicella and shift disease toward older age groups where it can be more severe.

Vaccine Effectiveness During a Varicella Outbreak Among Schoolchildren: Utah, 2002-2003

PEDIATRICS, 2005

Objectives. In the context of a chickenpox outbreak involving 2 Utah elementary schools, we conducted an investigation to assess vaccine effectiveness, describe illness severity, and examine risk factors for breakthrough varicella (ie, varicella in those who have been vaccinated). Methods. All parents were asked to complete a questionnaire about their child's medical history. Parents of children with recent varicella were interviewed, and vaccination records were verified. Lesions were submitted for polymerase chain reaction testing. Results. Questionnaires were returned for 558 (93%) of 597 students in school A and 924 (97%) of 952 students in school B. A total of 83 schoolchildren (57 unvaccinated and 26 vaccinated) had varicella during the October 2002 through February 2003 outbreak period. An additional 17 cases occurred among household contacts, including infants and adults. Polymerase chain reaction analysis recovered wild-type varicella. Vaccine effectiveness was 87%. With 1 notable exception, vaccinated children tended to have milder illness. Risk factors for breakthrough varicella included eczema, vaccination >5 years before the outbreak, and vaccination at <18 months of age. Restricting analysis to children vaccinated >5 years before the outbreak, those vaccinated at <18 months of age were more likely to develop breakthrough varicella (relative risk: 9.3; 95% confidence interval: 1.3-68.9). Conclusions. The vaccine, administered by >100 health care providers to 571 children during a 7-year time period, was effective. Risk factors for breakthrough varicella suggest some degree of biological interaction between age at vaccination and time since vaccination.

Varicella Susceptibility and Vaccination Strategies in Young Adults

The Journal of the American Board of Family Medicine, 1998

Background: Varicella infection causes substantial morbidity in young adults. Most military basic trainees are 18 to 21 years old, yet the Army has no varicella vaccination policy. We therefore determined varicella susceptibility in a population of Army basic trainees, examined variables that might predict antibody status, and developed a vaccination strategies model.

Varicella among Adults: Data from an Active Surveillance Project, 1995–2005

The Journal of Infectious Diseases, 2008

We report detailed population-based data on varicella among adults. In 2 US varicella active surveillance sites with high vaccine coverage among young children, the incidence of varicella among adults declined 74% during 1995-2005. A low proportion (3%) of adults with varicella had been vaccinated, with no improvement over the decade of program implementation, suggesting that the decline was likely secondary to herd-immunity effects. Compared with children, adults had more severe varicella in terms of both clinical presentation and frequency of complications. However, !30% of adults with varicella were treated with acyclovir. Among adolescents, illness severity was intermediate between that in children and adults. Varicella cases are preventable through vaccination. As we enter the second decade of the varicella vaccination program in the United States, we need to ensure that susceptible adolescents and adults are adequately protected from varicella by vaccination and that those who acquire varicella are appropriately treated with effective antiviral treatment.

Varicella Vaccine Effectiveness in Preventing Community Transmission in the 2-Dose Era

Pediatrics, 2016

We examined overall and incremental effectiveness of 2-dose varicella vaccination in preventing community transmission of varicella among children aged 4 to 18 years in 2 active surveillance sites. One-dose varicella vaccine effectiveness (VE) was examined in those aged 1 to 18 years. From May 2009 through June 2011, varicella cases identified during active surveillance in Antelope Valley, CA and Philadelphia, PA were enrolled into a matched case-control study. Matched controls within 2 years of the patient's age were selected from immunization registries. A standardized questionnaire was administered to participants' parents, and varicella vaccination history was obtained from health care provider, immunization registry, or parent records. We used conditional logistic regression to estimate varicella VE against clinically diagnosed and laboratory-confirmed varicella. A total of 125 clinically diagnosed varicella cases and 408 matched controls were enrolled. Twenty-nine case...

Importance of Catch-up Vaccination: Experience From a Varicella Outbreak, Maine, 2002-2003

PEDIATRICS, 2005

Objective. During December 2002 to January 2003, a varicella outbreak occurred in an elementary school in Maine. Just 1 month before detecting the outbreak, Maine implemented varicella vaccine requirements for child care but did not require vaccination for school entry. We investigated this outbreak to examine reasons for its occurrence, including vaccine failure.

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

The Journal of Infectious Diseases, 2000

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 vaccine's impact on mortality. Varicella is a highly infectious disease that is preventable by vaccine. Before vaccine licensure in 1995, ∼4 million cases per year resulted in р9300 hospitalizations [1] and 100 deaths each year [2]. Children bore the brunt of the health burden, accounting for 190% of cases, 66% of hospitalizations, and 45% of deaths (Centers for Disease Control and Prevention [CDC], unpublished data); however, the risk of severe complications and death was highest among infants, adults [2], and immunocompromised individuals [3, 4]. Moreover, complications and deaths were described commonly among previously healthy individuals [5-9]. Use of the varicella vaccine, which is recommended for routine use among susceptible people 112 months old [10, 11], is anticipated to alter the epidemiology of varicella by shifting the largest proportion of cases from children to adults. High vaccine coverage in childhood, especially if combined with a catch-up immunization program at adolescence, is expected to lead to a dramatic overall reduction in varicella cases and complications among both children and adults [12]. There has been no long-term, comprehensive analysis of varicella mortality for all age groups in the United States. We, therefore, analyzed national mortality data to characterize varicella deaths among United States residents during 1970-1994, the 25year period before varicella vaccine licensure. These data will serve as baseline data for an evaluation of the impact of the vaccination program on varicella mortality in the United States.

Vaccination against varicella as post-exposure prophylaxis in adults: A quantitative assessment

Vaccine, 2015

Background: Varicella can be severe in adults. When universal vaccination is not adopted, post-exposure prophylaxis has been recommended in adults with uncertain history of varicella to reduce the burden of the disease in adults, however its impact is not quantified. Methods: We developed a Bayesian probabilistic framework to estimate the impact of post-exposure prophylaxis in adults. We hypothesized that post-exposure vaccination would be proposed only after varicella exposure in close relatives. Information regarding the nature of the culprit exposure was obtained from a sample of 221 adult varicella cases. The lifelong probability that adults aged 18 would be infected with varicella was determined using data from the French Sentinelles surveillance network. Estimates of post-exposure vaccination efficacy were then used to compute the number of cases and hospitalizations prevented in adults. Results: Familial exposure to varicella was reported by 81 adult cases out of 221. The probability of infection after exposure was 32%, so that six exposures on average were necessary to explain the observed cumulated lifetime incidence of varicella in non-immune 18 years old and over adults. Among the 35% of the 18 years old population with uncertain history of varicella, 11% would truly be non-immune. Postexposure vaccination would prevent 26% of the cases (13 cases prevented per 100,000 adults per year) and 31% of the hospitalizations (0.2 hospitalizations prevented per 100,000 adults per year) if vaccination acceptance was 70%. An average of 16 adults would be vaccinated to avert one varicella case. Conclusions: Post-exposure vaccination is associated with a substantial decrease in the burden of the disease in adults in a country where universal vaccination is not recommended. This quantitative information may help inform professionals to uphold the recommendation.

Increasing Evidence of Immunity to Varicella Among Children in Massachusetts, 1999–2003

American Journal of Preventive Medicine, 2006

Background: Experiences with vaccine-preventable diseases have demonstrated the success of schoolentry requirements in increasing vaccination coverage and decreasing disease incidence. This study examines the effect of early implementation of daycare and school-entry requirements for varicella vaccination on recorded varicella immunity of preschool and school-aged children in Massachusetts. Methods: Immunization surveys were conducted in licensed child care centers and schools with kindergarten and/or 7th grades. Evidence of immunity to varicella was defined as having physician verified records of varicella vaccination or disease history from the 1999-2000 through 2003-2004 school years. Results: During the 5-year study period, physician-certified reliable history of varicella disease decreased in each grade level while vaccination coverage increased. The increase in the number of children in each grade level receiving varicella vaccine led to an increase in the overall percentage of children with evidence of immunity to varicella: 85% to 97% for children aged 2 years or more in child care, 93% to 98% for children in kindergarten, and 88% to 92% for children in 7th grade. Conclusions: The implementation of daycare and school-entry requirements for varicella vaccination within 4 years of the start of the varicella vaccination program in Massachusetts was associated with high levels of vaccination coverage in the cohorts of children targeted by the requirements. Although evidence of immunity from varicella disease decreased during the study period, the increase in varicella vaccination coverage compensated for the decline in disease history, resulting in a higher proportion of young children with evidence of immunity to varicella.