Varicella Vaccination Program Research Articles

Varicella Vaccine: Recognizing the Gap Years of Inadequate Vaccine Immunity

Varicella vaccination programs introduced in 1995 significantly reduced morbidity and mortality of the disease in the United States. Initiated as a single-dose vaccine, studies evaluating efficacy identified periodic reports of outbreaks prompting the implementation of the 2-dose varicella vaccination in 2007. The single-vaccine dose period, 1995 to 2007, produced a gap of 2-dose coverage for many individuals, now in their late teens to late 30s. Those in the vaccine gap are likely unaware of possible compromised immunity and may be at risk. Primary care providers should screen patients in this gap population, administer a second vaccine dose as needed, as well as be alerted to recognize symptoms of breakthrough disease in this cohort.

Varicella Seroprevalence in Pediatric Populations: Results from a Single-Center Study

Objective: Varicella is a highly contagious illness with potentially severe complications, especially in young children. In Turkey, the varicella vaccine was integrated into the Universal Varicella Vaccination program in 2013, targeting 12-month-old infants. While officially reported varicella cases have decreased considerably in the past two decades, underreporting remains a challenge. This study aimed to investigate varicella seropositivity in a tertiary center. Material and Methods: A qualitative immunoassay, the enzyme-linked immunosorbent assay (ELISA), was employed to detect anti-varicella antibodies. Serum samples were collected from individuals aged 4 to 18 residing in Turkey. Information on vaccination records, varicella history, and disease notification was also collected. Results: The varicella IgG antibody records were accessed for a total of 90 children. The overall prevalence of positive varicella antibodies was 58.0% (n=47) in the study population. Seropositivity rates were 67.2% for the 4-6 age group and 30% for the 7-12 age group. Notably, the 4-6 age group showed a significant association between seropositivity and age [p=0.005; OR=4.85; 95%CI (1.614-14.569)]. Conclusion: The seropositivity rate of 58% for chickenpox is concerning. In light of this, conducting more extensive studies will provide valuable guidance. It may be worth considering the administration of an additional dose of the varicella vaccine within the age range of 4-6 years. Further research is necessary to assess the potential benefits and feasibility of implementing such a vaccination strategy.

Clinical and Economic Burden of Antibiotic Use Among Pediatric Patients With Varicella Infection in the Outpatient Setting: A Retrospective Cohort Analysis of Real-world Data in France.

Varicella infects 90% of children before age 9. Though varicella is self-limiting, its complications may require antibiotics, though how antibiotics are utilized for varicella in France is not well known. This study assessed antibiotic use and costs associated with varicella and its complications in pediatric patients managed in the outpatient setting in France. A retrospective cohort study using the Cegedim Strategic Data-Longitudinal Patient Database, an electronic medical record database from general practitioners and office-based specialists in France, was conducted. Children <18 years old diagnosed with varicella between January 2014 and December 2018 with 3-month follow-up available were included. We used descriptive analysis to assess varicella-related complications, medication use, healthcare resource utilization and costs. Overall, 48,027 patients were diagnosed with varicella; 15.3% (n = 7369) had ≥1 varicella-related complication. Antibiotics were prescribed in up to 25.1% (n = 12,045/48,027) of cases with greater use in patients with complications (68.1%, n = 5018/7369) compared with those without (17.3%, n = 7027/40,658). Mean medication and outpatient varicella-related costs were €32.82 per patient with medications costing a mean of €5.84 per patient; antibiotics contributed ~23% to total costs annually. This study showed high antibiotic use for the management of varicella and its complications. A universal varicella vaccination program could be considered to alleviate complications and associated costs in France.

The Clinical and Economic Burden of Antibiotic Use in Pediatric Patients with Varicella Infection: a Retrospective Cohort Analysis of Real-World Data in England.

Varicella is a highly infectious disease, particularly affecting children, that can lead to complications requiring antibiotics or hospitalization. Antibiotic use for varicella management is poorly documented. This study assessed antibiotic use for varicella and its complications in a pediatric population in England. Data were drawn from medical records in the Clinical Practice Research Datalink and Hospital Episode Statistics datasets. Patients <18 years old diagnosed with varicella during 2014-2018 with 3-month follow-up available were included. We described varicella-related complications, medication use, healthcare resource utilization, and costs from diagnosis until 3-month post-diagnosis. We identified 114,578 children with a primary varicella diagnosis. 7.7% (n = 8,814) had a varicella-related complication, the most common being ear, nose, and throat related (37.1%, n = 3,271). In all, 25.9% (n = 29,706/114,578) were prescribed antibiotics. A higher proportion of patients with complications than those without complications were prescribed antibiotics (64.3%, n = 5,668/8,814 vs. 22.7%, n = 24,038/105,764). Mean annualized varicella-related costs were £2,231,481 for the study cohort. Overall, antibiotic prescriptions cost ∼£262,007. This study highlights high antibiotic use and healthcare resource utilization associated with varicella management, particularly in patients with complications. A national varicella vaccination program in England may reduce varicella burden and related complications, medication use, and costs.

Decline in varicella cases contacting primary health care after introduction of varicella vaccination in Finland – A population-based register study

A two-dose varicella vaccination programme at the age of 18 months and 6 years started in September 2017 in Finland with catch-up vaccinations, based on earlier modelling results, for children <12 years (born in 2006 or later) with no history of varicella. Nationwide population-based register data were used to assess the age-specific vaccination coverage and the annual incidence rates of varicella cases contacting public primary health care in 2014–2020. Age-specific incidence rates after (2022) and before (2014–2016) the implementation of the vaccination programme was compared by incidence rate ratios (IRR) with 95 % confidence interval.In 2019–2022, the first-dose coverage of varicella vaccination among children following the routine vaccination programme ranged from 85 to 87 % (children born in 2016 or later). The second-dose coverage was 58 % for the children born in 2016. The coverage of the catch-up vaccinations ranged from 18 % (children born in 2006) to 82 % (children born in 2015) for the first dose and from 10 % to 64 % for the second dose in the respective birth cohorts.In 2022, compared to the pre-vaccination period (2014–2016) the annual incidence rate of varicella cases contacting public primary health care declined in all age groups. The reduction ranged from 92 % to 98 % among the children eligible for the vaccinations (born 2006 or later). The 87 % reduction in the incidence rate among the unvaccinated children < 1 year suggests the indirect effect of the vaccinations.Introducing varicella vaccinations with catch-up was associated with rapid reduction in the varicella cases contacting primary health care in all ages. However, the coverage of the routine programme needs to be improved further as presently susceptibles accumulate and enable thus further outbreaks in coming decades.

Measles and Varicella Vaccination Program in a Hospital: Implementation and Impact on Contact Tracing.

Healthcare workers are recommended to get vaccinated against measles and varicella. This study aims to describe the implementation process of a measles and varicella vaccination program and report on the reduction in the number of susceptible healthcare workers exposed to measles, varicella, and disseminated herpes zoster at a tertiary hospital. The Consolidated Framework for Implementation Research (CFIR) model was used to describe the vaccination program implemented from October 2015 to September 2018. The number of exposed, reviewed, and susceptible healthcare workers during contact tracing for exposure to (a) measles and (b) varicella and disseminated herpes zoster in 2016, 2017, and 2018 is reported. A total of 6770 (95%) out of 7083 healthcare workers completed their immunization review by 2018. In 2016, 20 (10%) out of 198 healthcare workers exposed to measles were considered susceptible. In 2018, no one was found susceptible out of the 51 staff members exposed to measles (p < 0.01). For exposure to varicella and disseminated herpes zoster, seven (5%) out of 154 exposed healthcare workers were susceptible in 2016. In comparison, only two (1%) out of 377 exposed healthcare workers in 2018 were susceptible (p < 0.01). The vaccination program effectively reduced number of healthcare workers susceptible to measles, varicella, and disseminated zoster.

Impacts of routine varicella vaccination program and COVID-19 pandemic on varicella and herpes zoster incidence and health resource use among children in Japan

PurposeTo determine the epidemiological trends in pediatric varicella and herpes zoster incidence and changes in healthcare resource use from 2005 to 2022 using a nationally representative database in Japan. Materials and methodsWe conducted a retrospective observational study consisting of 3.5 million children with 177 million person-months during 2005–2022 using Japan Medical Data Center (JMDC) claims database in Japan. We investigated trends in incidence rates of varicella and herpes zoster and changes in healthcare resource use (e.g., antiviral use, office visits, and healthcare costs) over 18 years. Interrupted time-series analyses were used to investigate the impact of the routine varicella vaccination program in 2014 and infection prevention measures against COVID-19 on incidence rates of varicella and herpes zoster and related healthcare utilization. ResultsAfter the introduction of the routine immunization program in 2014, we observed level changes in incidence rates (45.6 % reduction [95 %CI, 32.9–56.0] of varicella cases, antiviral use (40.9 % reduction [95 %CI, 25.1–53.3]), and relevant healthcare costs (48.7 % reduction [95 %CI, 38.2–57.3]). Furthermore, infection prevention measures against COVID-19 were associated with additional level changes in varicella rates (57.2 % reduction [95 %CI, 44.5–67.1]), antiviral use (65.7 % reduction [59.7–70.8]), and healthcare costs (49.1 % [95 %CI, 32.7–61.6]). In contrast, the changes in incidence and healthcare costs for herpes zoster were relatively small, which showed 9.4 % elevated level change with a decreasing trend and 8.7 % reduced level change with a decreasing trend after the vaccine program and the COVID-19 pandemic. The cumulative incidence of herpes zoster in children born after 2014 was lower than that before 2014. ConclusionsVaricella incidence and healthcare resource use were largely affected by the routine immunization program and infection prevention measures against COVID-19, while these impacts on herpes zoster were relatively small. Our study indicates that immunization and infection prevention measures largely changed pediatric infectious disease practices.

Meningitis caused by the varicella vaccine virus in 17 immunized children and adolescents from the United States, Europe, and Japan

AbstractThe varicella vaccination program has an excellent safety record. The vaccine virus, like its wild‐type counterpart, can enter latency and later reactivate as herpes zoster. A lesser known but serious adverse event following reactivation is varicella vaccine meningitis. We investigate that adverse event. We performed a literature search using the PubMed and Google Scholar search engines to locate all published cases of varicella vaccine meningitis. We continued the search through January 2023. We found 17 cases of varicella vaccine meningitis. The first case was published in 2003, and the last case was published in 2023. The children lived in the United States, Greece, Germany, Switzerland, and Japan. Among the 17 cases, 14 were immunocompetent; nine of the 17 were adolescents. One potential risk factor was the administration of corticosteroids three to four weeks before the onset of meningitis. Varicella vaccine meningitis is a rare but one of the more serious adverse events that occurs several years following varicella vaccination. In immunocompetent children, this complication is treatable with a single course of intravenous acyclovir after hospitalization.

Chickenpox in Poland in 2020.

Chickenpox is an infectious disease caused by the varicella zoster virus. The characteristic feature of this virus is very high visibility of 90-95%. The most common connection is direct contact with the disease or via droplets. The United States was the first country to introduce a universal, population-based childhood varicella vaccination program in 1995. In its 25 years of implementation, this program has significantly reduced the burden of chickenpox. There was a more than 97% reduction in varicella incidence and a 90% reduction in varicella-related hospitalizations and deaths, the highest (99%) in those under the age of 20 (born after starting the vaccination programme). Chickenpox is very common in Poland. In recent years, starting from 2002, there has been an upward trend in the incidence of chickenpox, except for 2020. In 2020, a decrease in the number of cases was recorded. The aim of the study was to assess the epidemiological situation of chickenpox in Poland in 2020 and to compare it with the situation in previous years. Evaluation of the epidemiological situation of chickenpox in Poland in 2020 was based on the results of the analysis of aggregate data published in the annual bulletins: "Infectious diseases and poisonings in Poland in 2020." and "Vaccinations in Poland in 2020". In addition, recommendations from the Protective Vaccination Program for 2020 were used. In 2020, 71,567 cases of chickenpox were registered in Poland, i.e. 39.6% less than in the previous year. The incidence of chickenpox in 2020 was 186.6 per 100,000 and was lower than in 2019. The lowest incidence was recorded in the Świętokrzyskie Voivodship - 118.5/100,000, while the highest in the Kujawsko-Pomorskie Voivodeship - 263.5/100,000. Most cases concerned children aged 0-4 years (36,661). The incidence of chickenpox in men was higher than in women, and in rural areas higher than in urban dwellers. Hospitalization due to chickenpox in 2020 covered 1,368 people, which accounted for 0.51% of the total number of registered cases. In 2020, there was a decrease in the number of cases of chickenpox compared to the previous year. The lower incidence may have been the result of reduced transmission of the varicella virus due to changes in the health behavior of the population during the COVID-19 pandemic (isolation measures and the introduction of a lock down throughout Poland limiting the activity of the population).

Impact of implementing a free varicella vaccination policy on incidence in Wuxi City, China: an interrupted time series analysis.

Varicella vaccination is optional and requires self-payment. On 1 December 2018, Wuxi City launched a free varicella vaccination program for children. This study aimed to evaluate the changes in varicella incidence before and after the implementation of the policy. The data were obtained from official information systems and statistical yearbooks. We divided the period into chargeable (January 2017 to November 2018) and free (December 2018 to December 2021) periods. Interrupt time series analysis was used to conduct a generalised least-squares regression analysis for the two periods. A total of 51,071 varicella cases were reported between January 2017 and December 2021. After the implementation of the policy, there was a statistically significant decrease in the incidence of varicella (β2 = -0.140, P = 0.017), and the slope of the incidence also decreased by 0.012 (P = 0.015). Following policy implementation, the incidence decreased in all age groups, with the largest decline observed among children aged 8-14 years (β2 = -1.109, P = 0.009), followed by children aged ≤7 years (β2 = -0.894, P = 0.013). Our study found a significant reduction in the incidence of varicella in the total population after the introduction of free varicella vaccination in Wuxi City.

801. IDSA Featured Oral Abstract: 25 Years of Varicella Vaccination Program in the United States: Health Impact during 1995–2019

Abstract Background In 1995, the United States was the first country to introduce universal childhood varicella vaccination. High vaccine coverage was attained among young children, ≥ 90% since 2007. In 2007, the policy was changed from 1-dose to a 2-dose program. We describe the impact of 25 years of the U.S. varicella vaccination program on varicella disease nationally. Methods We reviewed published data and analyzed overall and age-specific trends for rates from the pre-vaccine period (1990–1994) through 2019 for varicella incidence using National Notifiable Diseases Surveillance System data, hospitalizations using National Inpatient Sample data, and deaths using National Center for Health Statistics data. We present trends in persons aged &amp;lt; 50 years, which captures most varicella burden and avoids misclassified herpes zoster in older people. Outbreak (≥ 5 varicella cases epidemiologically linked) characteristics were assessed for 1995–2019 and were informed by published data and analysis of surveillance data reported to CDC. Results Within the 10 years of the 1-dose program, varicella incidence, hospitalization, and mortality rates declined dramatically (71%–90%) vs. pre-vaccine. However, limited transmission continued in school settings which informed the change to a 2-dose policy. By 2019, declines reached &amp;gt; 97% for incidence and 94% and 97% for hospitalizations and deaths, respectively. The greatest decline occurred among persons aged &amp;lt; 20 years, born during the varicella vaccination program, with 99%, 97%, and &amp;gt; 99% reduction in incidence, hospitalizations, and deaths, respectively. The 2-dose program further reduced the number, size, and duration of outbreaks vs. the 1-dose program; over the entire program, the proportion of outbreaks with &amp;lt; 10 cases increased from 28% to 73%. Conclusion The varicella vaccination program significantly reduced varicella morbidity and mortality in the U.S. Twenty-five years into the program, pediatric varicella hospitalization has become a rare event and varicella deaths in persons aged &amp;lt; 20 years are practically eliminated in the U.S. Annually, &amp;gt; 3.8 million cases, 10,500 hospitalizations, and 100 deaths from varicella are now prevented in the United States due to the varicella vaccination program. Disclosures All Authors: No reported disclosures.

1461. The Impact of Universal Varicella Vaccination on Herpes Zoster Incidence in the United States

Abstract Background The varicella vaccination program was implemented in the United States in 1995 and has resulted in large reductions in varicella disease burden. At the start of the varicella vaccination program, impacts on herpes zoster (HZ) epidemiology were unknown. We used a large claims database to examine national HZ incidence during 1998–2019 in cohorts of persons born before and after varicella vaccine introduction. Methods Medical claims data were obtained from 1998–2019 IBM® MarketScan® Research Databases. We identified HZ based on first outpatient service with an HZ ICD-9/10 code (053.xx/B02.xx) and calculated age-specific incidence for persons aged ≥30 years (all born pre-vaccine) and persons aged 1–29 years (includes persons born post-vaccine). Results Among persons aged ≥30 years, HZ incidence increased with age and calendar time (Fig. 1); incidence in the two oldest age groups (60–69 and ≥70 years) started to decelerate in 2007. Among persons aged 1–29 years, HZ incidence increased early in the study period for the oldest age groups (born pre-vaccine, i.e., born after 1990), but later declined once each age group was comprised of persons born in the post-vaccine period (children and adolescents) (Fig 2); the peak incidence occurred in progressively-earlier calendar years among progressively younger age groups. Conclusion HZ incidence in persons aged ≥30 years increased early in the study period for all age groups followed by declines starting with the oldest cohorts. The U.S. data do not support previous modelled predictions that reduced VZV exposure would result in increased HZ incidence among adults. The patterns of decline in HZ incidence in persons aged 1–29 years can likely be explained by the success of the U.S. varicella vaccination program and increasingly uncommon latent infection with wild type varicella-zoster virus. These data suggest that continued declines in age-specific HZ incidence are likely as varicella vaccinated cohorts age. The reduction of HZ resulting from the varicella vaccination program, should ultimately extend to the entire U.S. population over time. Disclosures All Authors: No reported disclosures.

Safety of varicella vaccination strategies: An overview of reviews.

The safety of new vaccines under development as well as existing vaccines is a key priority for national and international public health agencies. A number of countries have implemented universal childhood varicella vaccination programmes over the past 30years. However, strategies differ in terms of the number of doses, type of vaccine(s) recommended, age at vaccination and interval between doses for a two-dose schedule. An overview of reviews was undertaken to assess the existing systematic review evidence of the safety of varicella vaccination strategies. The review was restricted to immunocompetent children aged 9months to 6years inclusive. A comprehensive search of databases, registries and grey literature was conducted up to 2 February 2022. Two reviewers independently screened, extracted data and assessed the methodological quality of included reviews. Overlap of included reviews was also assessed. A total of 17 reviews, incorporating both the monovalent varicella only and quadrivalent measles-mumps-rubella-varicella (MMRV) vaccines were included in the overview; six assessed the safety of one-dose strategies, four assessed the safety of two-dose strategies and 14 reviews did not specify the dosing strategy. The evidence suggests that mild local and systemic reactions are relatively common with varicella vaccination. Febrile seizures are also possible adverse effects of both the monovalent and quadrivalent MMRV vaccine, but serious adverse reactions are rare. While most reviews contained methodological flaws, and analysis by vaccine type and dosing strategy was restricted due to lack of detail in reporting of the reviews, there was clear and consistent evidence from a substantial evidence base, comprising 34 randomised controlled trials and 62 other primary studies/reviews, that varicella vaccination is safe.

Clinical efficacy and effectiveness of alternative varicella vaccination strategies: An overview of reviews.

A number of countries have implemented universal childhood varicella vaccination programmes over the past 30years. However, strategies differ in terms of dosing schedule (one- or two-dose), type of vaccine(s) recommended (monovalent, quadrivalent measles-mumps-rubella-varicella, or both), age at vaccination, and dosing interval for a two-dose schedule. An overview of reviews was undertaken to assess the existing systematic review evidence of the clinical efficacy/effectiveness of alternative varicella vaccination strategies. A comprehensive search of databases, registries and grey literature was conducted up to 2 February 2022. Two reviewers independently screened, extracted data and assessed the methodological quality of included reviews. A total of 20 reviews were included in the overview; 17 assessed the efficacy/effectiveness of one-dose strategies and 10 assessed the efficacy/effectiveness of two-dose strategies. Although the quality of most reviews was deemed 'critically low', there was clear and consistent evidence that vaccination is very effective at reducing varicella. While the analysis was restricted due to lack of detail in reporting of the reviews, the evidence suggests that two-dose strategies are more efficacious/effective than one-dose strategies in preventing varicella of any severity, but that both strategies have similar high efficacy/effectiveness in preventing moderate or severe varicella. Based on this evidence in this overview of reviews, a key consideration for policymakers on the possible introduction of a childhood varicella vaccination programme and the choice between a one- or two-dose strategy, will be whether the objective of a programme is to prevent varicella of any severity or to prevent moderate to severe varicella.

The health and economic impact of switching vaccines in universal varicella vaccination programs using a dynamic transmission model: An Israel case study

ABSTRACT Currently available health economic models for varicella infection are designed to inform the cost-effectiveness of universal varicella vaccination (UVV) compared with no vaccination. However, in countries with an existing UVV program, these models cannot be used to evaluate whether to continue with the current varicella vaccine or to switch to an alternative vaccine. We developed a dynamic transmission model that incorporates the historical vaccination program to project the health and economic impact of changing vaccination strategies. We applied the model to Israel, which initiated UVV in 2008 with a quadrivalent vaccine, MMRV-GSK, and switched to MMRV-MSD in 2016. The model was calibrated to pre-vaccination incidence data before projecting the impact of the historical and future alternative vaccination strategies on the clinical burden of varicella. Total costs and QALYs lost due to varicella infections were projected to compare continuing with MMRV-MSD versus switching to MMRV-GSK in 2022. Over a 50-year time horizon, continuing with MMRV-MSD reduced varicella incidence further by 64%, reaching 35 cases per 100,000 population by 2072, versus a 136% increase in incidence with MMRV-GSK. Continuing with MMRV-MSD reduced cumulative hospitalization and outpatient cases by 48% and 58% (vs. increase of 137% and 91% with MMRV-GSK), respectively. Continuing with MMRV-MSD resulted in 139 fewer QALYs lost with total cost savings of 3% compared with switching to MMRV-GSK, from the societal perspective. In Israel, maintaining the UVV strategy with MMRV-MSD versus switching to MMRV-GSK is projected to further reduce the burden of varicella and cost less from the societal perspective.

Decline in Severe Varicella Disease During the United States Varicella Vaccination Program: Hospitalizations and Deaths, 1990-2019.

To describe the impact of the US varicella vaccination program on severe varicella outcomes, we analyzed varicella hospitalizations using the National Inpatient Sample 1993-2019 and varicella deaths using the National Center for Health Statistics data 1990-2019. Over 25 years of vaccination program (1995-2019), varicella hospitalizations, and deaths declined 94% and 97%, respectively, among persons aged <50 years. Most of the decline (∼90%) occurred during the 1-dose period (through 2006/2007) by attaining and maintaining high vaccination coverage; additional declines occurred during the 2-dose period, especially in the age groups covered by the 2-dose recommendation. The greatest decline for both hospitalizations and deaths (97% and >99%, respectively) was among persons aged <20 years, born during the varicella vaccination program. In the <20 age group, varicella hospitalization has become a rare event, and varicella deaths have been practically eliminated in the United States. A total of >10 500 varicella hospitalizations and 100 varicella deaths are now prevented annually in the United States as a direct result of vaccination and reduction in varicella-zoster virus circulation.

The Impact of Universal Varicella Vaccination on Herpes Zoster Incidence in the United States: Comparison of Birth Cohorts Preceding and Following Varicella Vaccination Program Launch.

When the US varicella vaccination program was introduced in 1995, its impacts on the epidemiology of herpes zoster (HZ) were not precisely known. We used a large claims database to examine HZ incidence in the US during 1998-2019 among persons aged ≥30 years (the prevaccine cohort, born before 1990), and aged 1-29 years (includes the postvaccine cohort, born since 1990). We defined incident HZ as the first instance of an outpatient or emergency department (ED) claim with an HZ diagnostic code. Additionally, we examined the proportion of HZ visits among all ED visits as a complementary method to assess for healthcare-seeking artifacts in the findings. In persons aged ≥30 years (prevaccine cohort), we observed age-specific increases in HZ incidence during the earlier study years, with decelerations in later years, starting in 2007 with oldest age groups. Similar patterns were seen when we examined HZ visits as a proportion of all ED visits. For persons aged 1-29 years, age-specific HZ incidence increased early in the study period for the oldest age groups who were born prevaccine, but later declined in a stepwise pattern once each age group was comprised of persons born in the postvaccine period. Our results, corroborated with previously published studies, do not support prior modeling predictions that the varicella vaccination program would increase HZ incidence among adult cohorts who previously experienced varicella. Our findings also suggest that continued declines in age-specific HZ incidence as varicella-vaccinated cohorts age are likely.

Health and Economic Impact of the United States Varicella Vaccination Program, 1996-2020.

The aim of this study was to evaluate the health and economic impact of the varicella vaccination program on varicella disease in the United States (US), 1996-2020. Analysis was conducted using the Centers for Disease Control and Prevention or published annual population-based varicella incidence, and varicella-associated hospitalization, outpatient visit, and mortality rates in the US population aged 0-49 years during 1996-2020 (range, 199.5-214.2 million persons) compared to before vaccination (1990-1994). Disease costs were estimated using the societal perspective. Vaccination program costs included costs of vaccine, administration, postvaccination adverse events, and travel and work time lost to obtain vaccination. All costs were adjusted to 2020 US dollars using a 3% annual discount rate. The main outcome measures were the number of varicella-associated cases, hospitalizations, hospitalization days, and premature deaths prevented; life-years saved; and net societal savings from the US varicella vaccination program. Among US persons aged 0-49 years, during 1996-2020, it is estimated that more than 91 million varicella cases, 238 000 hospitalizations, 1.1 million hospitalization days, and almost 2000 deaths were prevented and 118 000 life-years were saved by the varicella vaccination program, at net societal savings of $23.4 billion. Varicella vaccination has resulted in substantial disease prevention and societal savings for the US over 25 years of program implementation.

Changing Epidemiology of Varicella Outbreaks in the United States During the Varicella Vaccination Program, 1995-2019.

We describe the changing epidemiology of varicella outbreaks informed by past and current active and passive surveillance in the United States by reviewing data published during 1995-2015 and analyzing new data from 2016 to 2019. Varicella outbreaks were defined as ≥5 varicella cases within 1 setting and ≥1 incubation period. During the 1-dose varicella vaccination program (1995‒2006), the number of varicella outbreaks declined by 80% (2003-2006 vs 1995-1998) in 1 active surveillance area where vaccination coverage reached 90.5% in 2006. During the 2-dose program, in 7 states with consistent reporting to the Centers for Disease Control and Prevention, the number of outbreaks declined by 82% (2016-2019 vs 2005-2006). Over the entire program (1995-2019), outbreak size and duration declined from a median of 15 cases/outbreak and 45 days duration to 7 cases and 30 days duration. The proportion of outbreaks with <10 cases increased from 28% to 73%. During 2016‒2019, most (79%) outbreak cases occurred among unvaccinated or partially vaccinated persons eligible for second-dose vaccination, highlighting the potential for further varicella control.

Prevention and Control of Nosocomial Varicella During the United States Varicella Vaccination Program Era.

The United States varicella vaccination program has successfully reduced varicella incidence and hospitalizations by ≥90%, consequently reducing the risk of nosocomial exposures. However, patients and healthcare personnel (HCP) continue to introduce varicella zoster virus (VZV) into healthcare settings. Herpes zoster (HZ) is less contagious than varicella, but it can also result in exposures. Unrecognized varicella and HZ may lead to extensive contact investigations, control efforts, and HCP furloughs that result in significant disruption of healthcare activities as well as substantial costs. Robust occupational health and infection prevention programs that ensure healthcare personnel immunity and prompt recognition and isolation of patients with varicella or HZ will lower the risk of VZV transmission and reduce or eliminate the need to furlough exposed HCP and associated costs.