Impact of a Routine Two-Dose Varicella Vaccination Program on Varicella Epidemiology

ArticleinPEDIATRICS 132(5) · October 2013with13 Reads
DOI: 10.1542/peds.2013-0863 · Source: PubMed
Abstract
Objective: One-dose varicella vaccination for children was introduced in the United States in 1995. In 2006, a second dose was recommended to further decrease varicella disease and outbreaks. We describe the impact of the 2-dose vaccination program on varicella incidence, severity, and outbreaks in 2 varicella active surveillance areas. Methods: We examined varicella incidence rates and disease characteristics in Antelope Valley (AV), CA, and West Philadelphia, PA, and varicella outbreak characteristics in AV during 1995-2010. Results: In 2010, varicella incidence was 0.3 cases per 1000 population in AV and 0.1 cases per 1000 population in West Philadelphia: 76% and 67% declines, respectively, since 2006 and 98% declines in both sites since 1995; incidence declined in all age groups during 2006-2010. From 2006-2010, 61.7% of case patients in both surveillance areas had been vaccinated with 1 dose of varicella vaccine and 7.5% with 2 doses. Most vaccinated case patients had <50 lesions with no statistically significant differences among 1- and 2-dose cases (62.8% and 70.3%, respectively). Varicella-related hospitalizations during 2006-2010 declined >40% compared with 2002-2005 and >85% compared with 1995-1998. Twelve varicella outbreaks occurred in AV during 2007-2010, compared with 47 during 2003-2006 and 236 during 1995-1998 (P < .01). Conclusions: Varicella incidence, hospitalizations, and outbreaks in 2 active surveillance areas declined substantially during the first 5 years of the 2-dose varicella vaccination program. Declines in incidence across all ages, including infants who are not eligible for varicella vaccination, and adults, in whom vaccination levels are low, provide evidence of the benefit of high levels of immunity in the population.
    • "[17] The universal use of varicella vaccine in young children has resulted in a 70%-98% decrease in the varicella incidence in the U.S. and other countries. [26][27][28]This policy provides varicella-specific immunity to most children prior to developing a malignancy and induces herd protection, decreasing the risk of transmission to those who lack adequate immunity due to their age, lack of response, or underlying disease. However, in many countries, including Guatemala, the risk of varicella morbidity for most children, does not clearly outweigh the costs of the universal vaccine program, in terms of both direct expenditure and resources diverted from other public health efforts. "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Varicella-zoster virus infection is associated with significant morbidity and mortality in immune-compromised children, despite treatment with antiviral agents. Universal varicella vaccine programs have significantly decreased this risk in many high-income countries, but in most low-income and middle-income countries, the burden of varicella in children treated for malignancy is poorly defi ned. Methods: We retrospectively reviewed records of children at the National Unit of Pediatric Oncology (UNOP) in Guatemala diagnosed with varicella between January 2009 and March 2013 in order to calculate incidence of varicella and evaluate morbidity, mortality, treatment interruption, and cost. Results: Fifty-nine cases of varicella were identified. Incidence was 23.4 cases per 1000 person-years (p-y). 66.1% of cases occurred in children with leukemia (median age 5.2 years; interquantile range 3.4-7 years) and 41.0% of these occurred during maintenance therapy. Source of exposure was identified for 14/59 (23.7%) children. Most were hospitalized (71.2%) and given intravenous acyclovir (64.4%). Eight (13.6%) children required critical care, and two (3.4%) died from disseminated varicella with multi-organ failure. Chemotherapy was delayed or omitted due to varicella in 50%. No signifi cant differences in outcomes based on nutritional and immunologic status were detected. The minimum average cost of treatment per episode was 598.75 USD. Conclusions: Varicella is a significant problem in children treated for cancer in Guatemala, where effective post-exposure prophylaxis is limited. In the absence of universal varicella vaccination, strategies to improve recognition of exposure and the future use of novel inactivated vaccines currently under investigation in clinical trials could mitigate this burden. World J Pediatr 2016;12(3):320-326
    Full-text · Article · Sep 2016
    • "The mean effectiveness for preventing moderate to severe disease and for preventing severe disease were 95% and 99%, respectively [50] . Additionally, the review found that two doses of the vaccine provided better protection than one dose against all grades of severity of varicella51525354. It is highly anticipated that the number of varicella cases in Japan would rapidly decline soon after the introduction of universal immunization because of the associated increase in the vaccine coverage. "
    [Show abstract] [Hide abstract] ABSTRACT: In 1974, Japanese scientists developed a live attenuated varicella vaccine based on the Oka strain. The efficacy of the vaccine for the prevention of varicella has been primarily demonstrated in studies conducted in the United States following the adoption of universal immunization using the Oka strain varicella vaccine in 1996. Although the vaccine was developed by Japanese scientists, until recently, the vaccine has been administered on a voluntary basis in Japan resulting in a vaccine coverage rate of approximately 40%. Therefore, Japan initiated universal immunization using the Oka strain varicella vaccine in November 2014. Given the transition from voluntary to universal immunization in Japan, it will also be important to monitor the epidemiology of varicella and herpes zoster.
    Full-text · Article · Mar 2016
    • "Varicella is preventable by vaccines that are generally considered safe and effective [3,5]. The USA introduced varicella vaccination in the national immunisation programme in 1995, Australia in 2000 and both countries have subsequently experienced a substantial decrease in disease burden678. Few countries in Europe have followed despite a consensus statement from European vaccine experts on the need for vaccination [5,9]. Germany, Greece, Cyprus, Latvia and Luxembourg have national childhood varicella vaccination programmes while the rest of Europe has heterogeneous or no official recommendations [5]. "
    [Show abstract] [Hide abstract] ABSTRACT: There is no consensus as regards the European varicella immunisation policy; some countries have introduced varicella vaccination in their routine childhood immunisation programs whereas others have decided against or are debating. With the aim of providing an overview of the epidemiology of varicella in Europe and addressing the different strategies and the experiences so far, we performed a review of epidemiological studies done in Europe from 2004 to 2014. Varicella is mainly a disease of childhood, but sero-epidemiological studies show regional differences in the proportion of susceptible adults. Hospitalisation due to varicella is not common, but complications and hospitalisation mainly affect previously healthy children, which underlines the importance of not dismissing varicella as a disease of little importance. The experience with universal vaccination in Europe shows that vaccination leads to a rapid reduction of disease incidence. Vaccine effectiveness is high and a protective herd effect is obtained. Experience with vaccination in Europe has not been long enough, though, to draw conclusions on benefits and drawbacks with vaccination as well as the capacity for national programs in Europe to maintain a sufficiently high coverage to prevent a change in age group distribution to older children and young adults or on the impact that varicella immunisation may have on the epidemiology of shingles. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Mar 2015
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