Impact of universal varicella vaccination on 1-year-olds in Uruguay: 1997-2005

Antimicrobial use for the management of varicella in Thailand: a retrospective observational study

OBJECTIVE

To describe the clinical characteristics of varicella patients seeking medical consultation and the use of antimicrobials for their management in Thailand in the absence of universal varicella vaccination (UVV).

METHODS

A multicenter, retrospective chart review of 260 children and adults with a primary diagnosis of varicella was conducted at one private and three public hospitals in Bangkok, Thailand. Charts of varicella patients (inpatient or outpatient) were randomly selected over a 5-year period. Key outcomes included clinical complications and the use of antibiotics, antivirals, and other medications.

RESULTS

Charts of 200 children (mean age 5.7 years, range 0.3-16 years) and 60 adults (mean age 27.9 years, range 18-50 years) were reviewed. Fourteen patients (including 8 children) were hospitalized. Five percent of the children and none of the adults were immunocompromised. At least 1 varicella-related complication was reported by 7.3% (7% of children, 8.3% of adults, p = .778) of all patients, including 57.1% (62.5% of children, 50% of adults) of inpatients (p < .001, compared with outpatients). Skin/soft tissue infection (47.7%) and dehydration (47.4%) were the most common complications. Antivirals (mainly oral acyclovir) were prescribed to 46.5% of patients (31.5% of children, 96.7% of adults, p < .001). Antibiotics were prescribed to 20.8% of patients (19% of children, 26.7% of adults, p = .199). Topical, oral, and intravenous antibiotics were prescribed to 12.3%, 8.5%, and 1.2% of patients, respectively. Antimicrobial prescriptions were higher among adults (p < .001) and immunocompromised patients (p = .025). Apart from antimicrobials, acetaminophen (62.3%) and oral antihistamines (51.5%) were the most prescribed.

CONCLUSION

A considerable number of varicella patients, both children and adults, seeking medical consultation in Thai hospitals are prescribed antibiotics and antivirals, with one-fifth of patients being prescribed an antibiotic and almost half prescribed an antiviral. The study may be of interest to policymakers in Thailand and other Asia-Pacific countries considering UVV implementation.

Global varicella vaccination programs

Varicella (chickenpox) is an infectious disease caused by the highly contagious varicella zoster virus with a secondary attack rate greater than 90%. From this perspective, we aimed to establish the basis for a national varicella vaccine policy by reviewing vaccination programs and policies of countries that have introduced universal varicella vaccinations. As a result of the spread of varicella, an increasing number of countries are providing 2-dose vaccinations and universally expanding their use. In practice, the efficacy and effectiveness of vaccination differ among vaccines and vaccination programs. Optimized vaccination strategies based on each country's local epidemiology and health resources are required. Accordingly, it is necessary to evaluate the effectiveness of varicella vaccines in different settings. Given the short-term and fragmented vaccine effectiveness evaluation in Korea, it is necessary to evaluate its effectiveness at the national level and determine its schedule based on the evidence generated through these studies.

Cost effectiveness and budget impact of universal varicella vaccination in Russia

This economic evaluation assesses the cost-effectiveness and budget impact of introducing a two-dose varicella vaccine in the Russian national immunization program. A static Markov model followed a simulated 2019 Russian cohort over its lifetime and compared outcomes and costs of three varicella vaccination strategies: strategy I (doses given at 12 and 15 months of age), strategy II (doses given at 1 year and 6 years of age), and a no vaccination scenario. Inputs on age-dependent clinical pathways, associated costs, and related health outcomes were collected from national sources and published literature. Results are presented as incremental cost-effectiveness ratio (ICER) from the healthcare payer and societal perspective over the lifetime of the birth cohort and the budget impact over a 10 years' time horizon. Vaccination strategies I and II resulted in an ICER of approximately 1.7 million rubles per quality-adjusted life years gained from the healthcare payer perspective and were cost-saving from the societal perspective. From the healthcare payer perspective, the costs per varicella case averted were 5,989 and 7,140 rubles per case for strategies I and II, respectively. However, from the societal perspective, vaccination is a dominant strategy and the budget impact analysis shows significant healthcare savings over 10 years, with strategy I realizing savings of ~2 billion rubles more than strategy II. From a public health impact perspective, varicella vaccination of children at 12 and 15 months of age through the Russian NIP is expected to be cost-effective with an affordable budget impact compared to no vaccination.

The impact of universal varicella vaccination on the clinical burden of varicella in Colombia: A National database Analysis, 2008-2019

In 2015, one-dose universal varicella vaccination (UVV) was introduced in the Colombian National Immunization Program targeting children aged 12 months, expanding to a two-dose program in 2019. This study aimed to examine the effect of one-dose UVV on the burden of varicella in Colombia. A retrospective study was conducted using national databases to estimate incidence and mortality for the target (1-4 years old), non-target (less than 1 and 5 years and older) and overall (all age groups) populations from the pre-UVV period (January 2008-June 2015) to the post-UVV period (July 2015-December 2019). A time-series analyses with ARIMA modeling was used to project expected varicella incidence and mortality in the absence of UVV in the post-UVV period. UVV impact was estimated by comparing predicted and observed values, providing point estimates and prediction intervals (PI). Overall vaccination coverage rate was over 90 % from 2016-2019. Following UVV introduction, mean annual incidence rates reduced from 743.6 to 676.8 per 100,000 in the target population and from 203.2 to 198.1 per 100,000 in the overall population. Our study estimated a reduction in varicella incidence from 2017, with the highest reduction of 70.5 % (95 % PI: 78.2-54.2) and 54.8 % (95 % PI: 65.0-36.4) observed in 2019 for the target and the overall populations, respectively. The ARIMA model estimated UVV in Colombia to have prevented 198,236 varicella cases from 2015 to 2019. Mortality reduced in the overall population from 0.8 per 1,000,000 to 0.5 per 1,000,000 and from 1.3 per 1,000,000 to 0.5 per 1,000,000 in the target population, in the pre-UVV and post-UVV periods, respectively. However, these differences were not statistically significant. Our study showed a significant reduction in varicella incidence after implementation of a one-dose UVV program in Colombia, increasing over time. Further assessment is needed to evaluate the impact of a two-dose UVV program in Colombia.

Trends in Varicella Burden of Disease Following Introduction of Routine Childhood Varicella Vaccination in Argentina: A 12-Year Time Series Analysis

One-dose universal varicella vaccination (UVV) was introduced in the Argentinian National Immunization Program in July 2015. This study examined the impact of one-dose UVV on varicella incidence and mortality in Argentina. Incidence and mortality data were obtained from official databases for pre-UVV (January 2008–June 2015) and post-UVV (July 2015–December 2019) periods. Time series analyses with autoregressive integrated moving average (ARIMA) modeling predicted varicella incidence and mortality in absence of UVV in the target (aged 1–4 years) and overall population. Predicted and observed values post-UVV were compared to estimate UVV impact. Mean annual incidence rates per 100,000 reduced from 1999 (pre-UVV) to 1122 (post-UVV) in the target population and from 178 to 154 in the overall population. Significant declines in incidence were observed, reaching reductions of 83.9% (95% prediction interval [PI]: 58.9, 90.0) and 69.1% (95% PI: 23.6, 80.7) in the target and overall populations, respectively, during peak months (September-November) post-UVV. Decreasing trends in mortality rate from 0.4 to 0.2 per 1,000,000 population were observed. Over the last four years, one-dose UVV has significantly reduced varicella burden of disease in Argentina. Continuous efforts to improve vaccination coverage rates and long-term follow-up are needed to better understand the benefits of the UVV program.

Chickenpox outbreak among Venezuelan immigrants housed in shelters and occupancies in the state of Roraima, Brazil, 2019: a descriptive study

OBJECTIVE

To describe chickenpox outbreak among Venezuelan immigrants in shelters and occupancies in the municipalities of Pacaraima and Boa Vista, the state capital of Roraima, Brazil, and the control measures implemented.

METHODS

This was a descriptive case series study, conducted between November 21 and December 13, 2019, based on secondary database obtained from the outbreak investigation made available by the General Coordination for the National Immunization Program. Descriptive analysis was performed using simple and relative frequency measurements, and measures of central tendency and dispersion were calculated.

RESULTS

Of the 9,591 immigrants, 38 active cases and 1,459 susceptible to varicella were identified. With regard to active cases, 23 were female, and those aged under 9 years (17 cases) were the most affected.

CONCLUSION

People susceptible to chickenpox were identified during the investigation. Immunization actions aimed at reducing transmission were adopted, thus preventing severe cases, deaths and overload in local health care system.

Impact of six years of routine varicella vaccination on the disease-related hospitalizations at Minas Gerais, Brazil

INTRODUCTION

The varicella vaccine was first introduced into the Brazilian immunization schedule in September 2013 as a single dose for children aged 15 months. In 2018, a second dose was recommended for individuals between 4 and 6 years old. This study aims to assess the impact of routine varicella vaccination on the number and profile of hospitalized varicella patients during the single dose period, as well as in the first two years after the adoption of the second dose.

METHODS

An observational retrospective study was conducted in an infectious disease pediatric hospital, in Minas Gerais, Brazil. Clinical as well as epidemiological data from patients hospitalized due to varicella between 2010 and 2019 were collected. Patients were split into groups based on the vaccine introduction: pre-vaccine period, single dose and two-dose period. They were compared by age, sex, reason for admission, illness-related complications and clinical outcome.

RESULTS

There were 1193 admissions due to varicella during the studied period. When compared with the pre-vaccine period, the number of hospitalizations decreased in 61.5% during the single-dose regime, reaching 95.2% in the two-dose period. Hospitalization rates decreased in all age groups, including non-vaccinated individuals such as those younger than 12 months (92.1%). As for reasons of admission, secondary bacterial skin infections were perceived to be the most common cause (>70%). A reduction was also seen in admission of immunocompromised or HIV positive patients (84.8%).

CONCLUSION

The collected data shows a significant impact in the number of hospital admissions due to varicella after six years of the implementation of the vaccine, positively affecting both vaccinated and non-vaccinated individuals. Further reduction was seen after the second dose was initiated, but its true impact will only be understood fully after a longer period of continuous vaccination.

A randomized trial assessing the efficacy, immunogenicity, and safety of vaccination with live attenuated varicella zoster virus-containing vaccines: ten-year follow-up in Russian children

In Russia, a universal varicella vaccination (UVV) program has not been implemented, and varicella vaccination coverage is low. We assessed the efficacy, antibody persistence, and safety of one- and two-dose varicella vaccination schedules in Russian children with a ten-year follow-up period, as part of an international phase IIIB, observer-blind, randomized, controlled trial (NCT00226499). Children aged 12-22 months were randomized (3:3:1) to receive two doses of tetravalent measles-mumps-rubella-varicella vaccine (V2 group), one dose trivalent measles-mumps-rubella (MMR) vaccine and one dose of varicella vaccine (V1 group), or two doses of MMR vaccine (V0 [control] group), 42 days apart. Main study outcomes were: vaccine efficacy (VE) against confirmed varicella cases, anti-varicella zoster virus (VZV) seropositivity rates and geometric mean concentrations, and reporting of (serious) adverse events ([S]AEs). The total vaccinated cohort in Russia comprised 1000 children; 900 were followed up until study end (year [Y] 10). VE estimates against confirmed varicella (Y10) were 92.4% in the V2 group and 74.7% in the V1 group. Anti-VZV seropositivity rates remained ≥99.4% in the V2 group and ≥89.7% in the V1 group from day 42 post-vaccination 2 until Y10. Occurrence of (un)solicited AEs and SAEs was similar across groups and confirmed the safety profile of the vaccines. No vaccination-related SAEs or deaths were reported. These results are consistent with the global trial results, i.e., the highest VE estimates observed following the two-dose schedule compared to the one-dose schedule. These data may inform decision-making related to potential implementation of a UVV program.

Incidence of varicella and herpes zoster after inclusion of varicella vaccine in national immunization schedule in Turkey: time trend study

The aim of the study was to investigate changes in the incidences of Varicella and Herpes Zoster (HZ) following introduction of single dose Varicella vaccine (VV) in Turkey. Changes in the incidences of varicella and HZ per 100,000 population were compared with pre (2011-2012) and post-VV period (2018-2019) throughout years between years 2011 and 2019 both for children and adults. In children ≤5 years of age, the annual incidences of varicella significantly decreased from 290 per 100000 children in 2011 to 24 per 100000 children in 2019 [p = .0001]. Also, for children ≤5 years the mean annual incidence of varicella decreased significantly [326/100000 ±51/100000 vs 23/100000 ± 1/100000; p = .014] between pre- and post-VV period. Moreover, the annual incidences of varicella significantly decreased from 43 per 100000 children in 2011 to 26 per 100000 children in 2019 in children age between 6 and 17 years. On the other hand, incidence of varicella in adult population (age >17 years) did not change significantly. Besides, the annual incidences of Herpes Zoster did not change significantly in children age stratas but significant increment observed in adult population. This increment was significant in adult age strata of 18-44 years, but non-significant in age strata of 45-64 years and >64 years. Thus, our study showed a significant reduction in the incidences of Varicella in children age stratas whereas significant increment in the incidence of HZ in adult population after the implementation of VV into the NIP of Turkey.

Incidence of varicella and herpes zoster after inclusion of varicella vaccine in national immunization schedule in Turkey: time trend study

The aim of the study was to investigate changes in the incidences of Varicella and Herpes Zoster (HZ) following introduction of single dose Varicella vaccine (VV) in Turkey. Changes in the incidences of varicella and HZ per 100,000 population were compared with pre (2011-2012) and post-VV period (2018-2019) throughout years between years 2011 and 2019 both for children and adults. In children ≤5 years of age, the annual incidences of varicella significantly decreased from 290 per 100000 children in 2011 to 24 per 100000 children in 2019 [p = .0001]. Also, for children ≤5 years the mean annual incidence of varicella decreased significantly [326/100000 ±51/100000 vs 23/100000 ± 1/100000; p = .014] between pre- and post-VV period. Moreover, the annual incidences of varicella significantly decreased from 43 per 100000 children in 2011 to 26 per 100000 children in 2019 in children age between 6 and 17 years. On the other hand, incidence of varicella in adult population (age >17 years) did not change significantly. Besides, the annual incidences of Herpes Zoster did not change significantly in children age stratas but significant increment observed in adult population. This increment was significant in adult age strata of 18-44 years, but non-significant in age strata of 45-64 years and >64 years. Thus, our study showed a significant reduction in the incidences of Varicella in children age stratas whereas significant increment in the incidence of HZ in adult population after the implementation of VV into the NIP of Turkey.

Hospitalization for acute cerebellitis in children affected by varicella: how much does it cost?

Background

Chickenpox is a highly contagious airborne disease caused by the varicella zoster virus. It is generally benign and self-limiting, but it may be responsible of life-threatening complications. Acute cerebellitis (AC) is the most common neurological complication and is associated with prolonged hospitalization in the acute phase (HAP).

Aim of the study

To estimate the costs of AC HAP in children affected by varicella.

Materials and methods

We retrospectively reviewed the medical records of a pediatric cohort hospitalized for chickenpox AC over a period of 15 years (from October 2003 to October 2018) and we analyzed acute care costs. For any patient the HAP has been calculated. The final value includes cost of hospital accommodation and management at the Pediatric and Infectious Diseases Unit. To this cost, the price of procedures (imaging, laboratory exams, medical and paramedical evaluations) and medical treatments was added.

Results

In the study period, 856 children had been hospitalized for varicella. Out of them, 65 met a diagnosis of AC and were included in the study. The hospitalization length was of 10 days (range 3–20 days). The median cost of HAP for each patient was of 5366 euro, with an average annual cost of 23,252 €. The most significant part of HAP is due to the cost of hospital accommodation and management at the Pediatric Infectious Diseases Unit, which was about € 537.78 for a single day.

Discussion

Although AC post-varicella is rare, its HAP cost is not negligible resulting in substantial economic burden. Vaccination would have probably prevented varicella and AC complication, avoiding hospitalization.

Conclusions

Financial studies are important for evaluate the cost saving in order to influence public funding decisions. Further studies are necessary to investigate the economic burden of the disease.

NUMBER OF CASES OF VARICELLA AND HOSPITALIZATION IN A PEDIATRIC REFERENCE HOSPITAL IN BRAZIL AFTER INTRODUCING THE VACCINE

OBJECTIVE

To assess the number of cases and the profile of hospitalizations from varicella after the introduction of the measles, mumps, rubella and varicella combination vaccine in the public health system.

METHODS

Retrospective study in an infectious diseases pediatric hospital of reference in Southeast Brazil. The cases with a clinical diagnosis of varicella, from January 2011 to June 2016, were assessed from pediatricians' medical records. The hospitalizations were classified into a pre-vaccine group and post-vaccine group, based on the date the vaccine was introduced (September 2013). Both groups were compared by age, sex, time of hospitalization, reason for hospitalization, hospital complications, duration of intensive care, and clinical outcome.

RESULTS

A total of 830 hospitalizations were recorded; 543 in the pre-vaccine period and 287 in the post-vaccine period, a reduction of 47.1% (p<0.001). In both periods, a similar profile in the hospitalizations was noticed: majority male; aged between one to five years old; most complications due to secondary causes (mainly skin infections); main outcome was clinical improvement and discharge from the hospital. In the pre-vaccine period, six deaths were recorded and two were recorded in the post-vaccine period.

CONCLUSIONS

The profile of the hospitalizations was expected to stay the same since this study did not compare vaccinated with unvaccinated children, but hospitalizations before and after the vaccine was introduced. In accordance with the medical literature, we found a significant fall in the number of hospitalizations from varicella.

Spatiotemporal Epidemiology of Varicella in Chongqing, China, 2014-2018

Although immunization against varicella using vaccines has been proven to be significant and effective in the past decades, varicella remains a major public health concern for many developing countries. Varicella vaccination has not been introduced into routine immunization programs in China, and varicella outbreaks have continued to occur. Taking the city of Chongqing, which has a high prevalence of varicella, as an example, this study explored the spatiotemporal epidemiology of varicella. Based on the reported data of varicella cases from 1 January 2014 to 31 December 2018 in Chongqing, hot spots and space-time clusters of varicella were identified using spatial autocorrelation analysis and scan statistics. Within this period, a total of 112,273 varicella cases were reported in Chongqing (average annual incidence: 73.44 per 100,000), including one death. The incidence of varicella showed an increasing trend with significant seasonal peaks, which occurred during April to July and October to January of the following year. The total ratio of male to female patients affected was 1.10:1. Children under the age of 15 and students accounted for the majority of the patient population. The hotspots detected through local spatial autocorrelation analysis, and the most likely clusters identified by scan analysis, were primarily in the main urban districts of Chongqing. The secondary clusters were mostly detected in northeast and southwest Chongqing. There were obvious spatial dependence and spatiotemporal clustering characteristics of varicella in Chongqing from 2014 to 2018. High-risk districts, populations, and peak periods were found in this study, which could be helpful in implementing varicella prevention and control programs, and in adjusting vaccination strategies for the varicella vaccine based on actual conditions.

Impact of vaccination on the incidence of varicella hospitalizations in a state in Southeast Brazil

INTRODUCTION

This study aimed to analyze cases of complicated varicella and the impact of varicella vaccination in Minas Gerais, Brazil.

METHODS

This was a time series study of a territorial basis using data on varicella cases from 2010 to 2016, which was provided by the State Health Department of Minas Gerais on . Descriptive statistics were used for the analysis, and the generalized linear regression model proposed by Prais-Winsten was used for the time tendency, adopting a significance level of 5% and the integrated autoregressive modeling of moving averages.

RESULTS

There were 1,635 cases of varicella; out of which cellulitis (44%) was the predominant complication. The home-acquired cases were 38.9% and 464 cases (40.6%) were not previously vaccinated. There was a significant decrease in the incidence coefficient when comparing the pre- and post- immunization periods, from 1.95 cases/100,000 inhabitants in 2010 to 0.24 cases/100.000 inhabitants in 2016 (p<0.05). There was a higher incidence of cases recorded among males, with higher prevalence in the age group of 1-4 years (54.7%). Lethality was higher between 5-9 years of age (44%). Mortality was higher in the age group of 0-4 years and among females (2.58/100,000 inhabitants/year). The overall trend of the incidence coefficient was a decreasing one, with an annual percentage variation.

CONCLUSIONS

The number of complicated varicella cases notified decreased, coincidentally, in the post-immunization period. However, the immunization coverage period was restricted for the assessment of the correlation between immunization coverage and incidence.

Evaluation of impact of one dose varicella vaccine on the incidence of chickenpox in Argentina

INTRODUCTION

Varicella, also known as chickenpox is one of the most common immunizable diseases. In 1998, the World Health Organization (WHO) recommended to incorporate this vaccine in the national immunization programs, which Argentina did in 2015.

OBJECTIVES

To describe the behavior of the varicella time series for the 2005-2017 period, and to evaluate the impact of the vaccine in Argentina.

METHODOLOGY

An ecological observational study was performed, using the varicella cases reported in the National Health Monitoring System, and the data of the National census as secondary data sources. A model based time series analysis of the notified varicella cases in Argentina was performed, using a Negative Binomial Mixed Model. For the verification of the vaccine impact, the 2005-2014 period was selected, and a prognosis for the following years was performed. Impact was evaluated by comparing the rates and confidence intervals between the predicted and observed values.

RESULTS

Argentina reported 1,775,587 varicella cases for the 2005-2017 period. The series exhibited seasonality, and, a decreasing trend in the number of cases was observed in 2016 and 2017. A reduction of the incidence rate after the implementation of the vaccine was observed. The transmission risk decreased in the country after vaccine implementation.

CONCLUSIONS

This study is the first concrete evidence of the varicella incidence decline after the implementation of a single dose application program in Argentina.

Burden of varicella in Latin America and the Caribbean: findings from a systematic literature review

Background

Varicella is typically mild and self-limiting, but can be associated with complications and even death. The limited data available on varicella in Latin America and the Caribbean (LAC) indicate substantial burden in countries where varicella vaccine is not part of publicly funded childhood national immunization programs.

Methods

A systematic literature review of published studies was complemented by “gray” literature on varicella incidence, complications, mortality, and economic consequences, in the absence and presence of universal varicella vaccination (UVV) in LAC.

Results

Seroprevalence data indicate that varicella is usually a disease of childhood in LAC. Varicella incidence rates, while unreliable in the absence of mandatory reporting, show a trend to increased incidence due to greater urbanization and population density. The introduction of UVV in national immunization programs has led to significant reductions in varicella incidence in these areas.

Conclusions

Varicella continues to pose a substantial healthcare burden in LAC. The future introduction of UVV in additional countries is predicted to provide substantial reductions in cases, with important economic benefits. For countries that have already implemented UVV, the challenge is to maintain high rates of coverage and, where relevant, consider inclusion of a second dose to reduce breakthrough cases. Given the significant proportion of the region now implementing UVV, a regional recommendation in order to prevent any potential for age-shifts in varicella infection might be considered.

Electronic supplementary material

The online version of this article (10.1186/s12889-019-6795-0) contains supplementary material, which is available to authorized users.

Protection against varicella with two doses of combined measles-mumps-rubella-varicella vaccine or one dose of monovalent varicella vaccine: 10-year follow-up of a phase 3 multicentre, observer-blind, randomised, controlled trial

BACKGROUND

The duration of protection provided by varicella vaccines is unclear. We assessed the 10-year vaccine efficacy of two doses of a combined measles-mumps-rubella-varicella vaccine (MMRV), one live attenuated varicella vaccine (V) dose given after one measles-mumps-rubella vaccine (MMR) dose (MMR + V), versus two MMR doses (control vaccine) for the prevention of confirmed varicella.

METHODS

This was a phase 3b follow-up of an observer-blinded, randomised, controlled trial. In phase a, children aged 12-22 months (at first vaccination) from Czech Republic (Czechia), Greece, Italy, Lithuania, Norway, Poland, Romania, Russia, Slovakia, and Sweden were randomly assigned by computer-generated randomisation list (3:3:1) to receive two doses of MMRV, one dose of MMR and one dose of varicella vaccine, or two doses of MMR, 42 days apart. Varicella cases were confirmed by detection of viral DNA, or epidemiological link and clinical assessment, by an independent data monitoring committee; disease severity was based on a modified Vázquez scale. Hazard ratios for MMRV and MMR + V versus MMR estimated in the per-protocol cohort using a Cox proportional hazards regression model were used to calculate vaccine efficacy and 95% CI. Serious adverse events were recorded throughout the study in all vaccinated children. Study objectives were secondary and descriptive. The trial is registered at ClinicalTrials.gov, number NCT00226499.

FINDINGS

Between Sept 1, 2005, and May 10, 2006, 5803 children (mean age 14·2 months, SD 2·5) were vaccinated. The per-protocol cohort included 2279 children from the MMRV group, 2266 from the MMR + V group, and 744 from the MMR group. From baseline to a median follow-up of 9·8 years, 76 (3%) children in the MMRV group, 469 (21%) in the MMR + V group, and 352 (47%) in the MMR group had varicella. Vaccine efficacy against all varicella was 95·4% (95% CI 94·0-96·4) for MMRV and 67·2% (62·3-71·5) for MMR + V; vaccine efficacy against moderate or severe varicella was 99·1% (97·9-99·6) for MMRV and 89·5% (86·1-92·1) for MMR + V. During phase b, serious adverse events were reported by 290 (15%) of 1961 children in the MMRV group, 317 (16%) of 1978 in the MMR + V group, and 93 (15%) of 641 in the MMR group. There were no treatment-related deaths.

INTERPRETATION

The 10-years vaccine efficacy observed, suggests that a two-dose schedule of varicella vaccine provided optimum long-term protection for the prevention of varicella by offering individual protection against all severities of disease and leading to a potential reduction in transmission, as observed in the US experience with universal mass vaccination.

FUNDING

GlaxoSmithKline Biologicals.

Global impact of varicella vaccination programs

Although varicella is usually a mild and self-limited disease, complications can occur. In 1998, the World Health Organization recommended varicella vaccination for countries where the disease has a significant public health burden. Nonetheless, concerns about a shift in the disease to older groups, an increase in herpes zoster in the elderly and cost-effectiveness led many countries to postpone universal varicella vaccine introduction. In this review, we summarize the accumulating evidence, available mostly from high and middle-income countries supporting a high impact of universal vaccination in reductions of the incidence of the disease and hospitalizations and its cost-effectiveness. We have also observed the effect of herd immunity and noted that there is no definitive and consistent association between vaccination and the increase in herpes zoster incidence in the elderly.

Economic burden of varicella in children 1-12 years of age in Argentina, 2009-2014

BACKGROUND

In Argentina, varicella vaccination was included in the national schedule for mandatory immunizations in 2015. The vaccine has been shown to substantially reduce the morbidity and mortality associated with the virus. The purpose of this study was to evaluate the clinical and economic burden associated with varicella in Argentina prior to vaccine introduction.

METHODS

This was a multi-center, retrospective chart review study among patients aged 1-12 years with a primary varicella diagnosis in 2009-2014 in Argentina. Healthcare resource utilization (HCRU) associated with varicella and its complications, unit costs, and work loss were used to estimate direct and indirect costs. All costs are presented in 2015 United States dollars (USD).

RESULTS

One hundred and fifty children with varicella were included (75 outpatients, 75 inpatients), with a mean age of 3.8 (SD = 2.4) and 2.9 (SD = 2.2) years, respectively. One or more complications were experienced by 28.0% of outpatients and 98.7% of inpatients, the most common being skin and soft tissue infections, pneumonia, sepsis, cerebellitis, and febrile seizure. HCRU estimates included use of over-the-counter (OTC) medications (58.7% outpatients, 94.7% inpatients), prescription medications (26.7% outpatients, 77.3% inpatients), tests/procedures (13.3% outpatients, 70.7% inpatients), and consultation with allied health professionals (1.3% outpatients, 32.0% inpatients). The average duration of hospital stay was 4.9 (95% CI = 4.2-5.7) days, and the average duration of ICU stay was 4.8 (95% CI = 1.6-14.1) days. The total combined direct and indirect cost per varicella case was 2947.7 USD (inpatients) and 322.7 USD (outpatients). The overall annual cost of varicella in Argentina for children aged ≤14 years in 2015 was estimated at 40,054,378.0 USD.

CONCLUSION

The clinical burden of varicella in Argentina was associated with utilization of significant amounts of healthcare resources, resulting in substantial economic costs. These costs should be reduced with the recent implementation of routine vaccination of children.

Single-dose varicella vaccine effectiveness in Brazil: A case-control study

BACKGROUND

Varicella vaccine was introduced into the Brazilian Immunization Program in October 2013, as a single-dose schedule administered at 15 months of age. Its effectiveness had not yet been assessed in the country.

METHODS

A matched case-control study was carried out in São Paulo and Goiânia (Southeast and Midwest regions, respectively), Brazil. Suspected cases, were identified through a prospective surveillance established in the study sites. All cases had specimens from skin lesion collected for molecular laboratory testing. Cases were confirmed by either clinical or PCR of skin lesions and classified as mild, moderate, and severe disease. Two neighborhood controls were selected for each case. Cases and controls were aged 15-32 months and interviewed at home. Evidence of prior vaccination was obtained from vaccination cards. Univariate and multivariate logistic regression models were used, and odds ratio and its respective 95% confidence intervals were estimated. Vaccine effectiveness was estimated by comparing de odds of having received varicella vaccine among cases and controls.

RESULTS

A total of 168 cases and 301 controls were enrolled. Moderate and severe illness, was found in 33.3% and 9.9% of the cases. Effectiveness of a single dose varicella vaccine was 86% (95%CI 72-92%) against disease of any severity and 93% (95%CI 82-97%) against moderate and severe disease. Out of 168 cases, 81.8% had positive PCR results for wild-type strains, and 22.0% were breakthrough varicella cases. Breakthrough cases were milder compared to non-breakthrough cases (p < .001).

CONCLUSIONS

Effectiveness of single dose varicella vaccine in Brazil is comparable to that in other countries where breakthrough varicella cases have also been found to occur. The goal of the varicella vaccination program, along with disease burden and affordability should be taken into consideration when considering the adoption of a second dose of varicella vaccine into national immunization programs.

One or two doses of live varicella virus-containing vaccines: Efficacy, persistence of immune responses, and safety six years after administration in healthy children during their second year of life

BACKGROUND

This phase III B follow-up of an initial multicenter study (NCT00226499) will evaluate the ten-year efficacy of two doses of the combined measles-mumps-rubella-varicella vaccine (MMRV) and one dose of the live attenuated varicella vaccine (V) versus a measles-mumps-rubella control group (MMR) for the prevention of clinical varicella disease. Here we present efficacy results for six years post-vaccination.

METHODS

In phase A of the study, healthy children aged 12-22 months from ten European countries were randomized (3:3:1) and received either two doses of MMRV, or one dose of combined MMR and one dose of monovalent varicella vaccine (MMR+V), or two doses of the MMR vaccine (control), 42 days apart. Vaccine efficacy against all and against moderate or severe varicella (confirmed by detection of viral DNA or epidemiological link) was assessed from six weeks up to six years post-dose 2 for the MMRV and MMR+V groups, and was calculated with 95% confidence intervals (CI). The severity of varicella was calculated using the modified Vázquez scale (mild ≤ 7; moderately severe = 8-15; severe ≥ 16). Herpes zoster cases were also recorded.

RESULTS

5289 children (MMRV = 2279, mean age = 14.2, standard deviation [SD] = 2.5; MMR+V = 2266, mean age = 14.2, SD = 2.4; MMR = 744, mean age = 14.2, SD = 2.5 months) were included in the efficacy cohort. 815 varicella cases were confirmed. Efficacy of two doses of MMRV against all and against moderate or severe varicella was 95.0% (95% CI: 93.6-96.2) and 99.0% (95% CI: 97.7-99.6), respectively. Efficacy of one dose of varicella vaccine against all and against moderate or severe varicella was 67.0% (95% CI: 61.8-71.4) and 90.3% (95% CI: 86.9-92.8), respectively. There were four confirmed herpes zoster cases (MMR+V = 2, MMR = 2), all were mild and three tested positive for the wild-type virus.

CONCLUSIONS

Two doses of the MMRV vaccine and one dose of the varicella vaccine remain efficacious through six years post-vaccination.

Early impact of universal varicella vaccination on childhood varicella and herpes zoster hospitalizations in Brazil

INTRODUCTION

The Brazilian childhood National Immunization Program (NIP) introduced live and attenuated varicella vaccination in a single dose, combined as tetraviral vaccine, at 15 months of age in the whole country, during September to December of 2013. The aim of this study was to report trends in incidence of childhood hospital admissions related to varicella and zoster in Brazil from 2003 to 2016, including the first three years after vaccine introduction.

METHODS

The number and incidence of hospital admission in patients aged less than 20 years in Brazilian public health system with an admission diagnosis of varicella and zoster from 2003 to 2016 were analyzed and pre (2003-2013) and post-vaccination periods (2014-2016) were compared. The data were obtained from DATASUS, a Brazilian government's open-access public health database system, and analyzed adjusting for secular trend and seasonality if a statistically significant change was found.

RESULTS

During the study period, 69,791 admissions due to varicella and herpes zoster occurred in the children younger than 20 years. After adjusting for seasonality, the incidence of hospitalizations decreased from 27.33 to 14.33 per 100000 per year, which corresponds to a reduction of 47.6% (95% confidence interval 18.19-77.04%, p < 0.001) in the vaccinated age group (1-4 years) in 2014-2016 compared to pre-vaccination period. The changes were not significant in the unvaccinated age groups.

CONCLUSION

The hospitalizations due to varicella and herpes zoster were decreased by half early after the introduction of a single dose of tetraviral vaccine in NIP in the vaccinated children. Further studies may assess duration and intensity of this effect, as well as the indirect effect in the unvaccinated age groups.

Severe varicella in persons vaccinated with varicella vaccine (breakthrough varicella): a systematic literature review

INTRODUCTION

Varicella vaccines are highly effective at preventing disease, but varicella may occur among vaccinated persons (termed breakthrough varicella). Breakthrough varicella is generally mild, but severe cases have been reported. The objective of this review is to describe severe breakthrough varicella. Areas covered: We conducted a systematic review of articles published during 1974-2016. A total of 34 articles were included in our review: 21 described breakthrough varicella with disseminated varicella-zoster virus (VZV) infection with other organ involvement in addition to skin (none among two-dose vaccinees); 9 described hospitalized breakthrough varicella without mention of other organ involvement in addition to skin (of which 2 reported 4 two-dose vaccinees); and 4 described both. A total of 52-60 unique breakthrough varicella cases with disseminated VZV infection with other organ involvement in addition to skin reported with the following complications, not mutually exclusive: pneumonia (n = 8-9 cases), neurologic (n = 18-24 cases), hematologic (n = 10-11 cases), ocular (n = 5 cases), renal (n = 2 cases), hepatic (n = 3 cases), secondary infection with bacteremia or sepsis (n = 8 cases), and other complication (n = 4 cases). There were 6 cases of fatal breakthrough varicella. Expert commentary: With >31 million doses distributed annually worldwide since 2007, severe breakthrough varicella can occur but they appear to be uncommon.

Modelling Hospitalisation Ratios for Febrile Convulsions and Severe Varicella Under Combined Measles, Mumps, Rubella, and Varicella (MMRV-Priorix-Tetra™) Compared to Separate MMR + V Vaccination

Introduction

Measles, mumps, rubella, and varicella combination vaccines (MMRV) facilitate varicella vaccination uptake compared with separate administration of measles, mumps, and rubella vaccine (MMR) with varicella vaccine (V). However, the risk of developing febrile convulsions (FC) is higher in children vaccinated with MMRV.

Objectives

The aim was to demonstrate how to put the increased FC risk associated with MMRV into perspective by comparing it with the lower V-coverage risk associated with MMR + V.

Methods

FC and varicella burdens were measured by total numbers or duration of hospitalisations. A model, based on several assumptions and integrating parameters from heterogeneous data sources relevant to Germany, was developed to evaluate hospitalisation ratios (HRs; ratios between yearly numbers of varicella-related hospitalisation days prevented by MMRV and yearly numbers of FC-related hospitalisation days attributed to MMRV, both compared with MMR + V). A sensitivity analysis estimated HR under different scenarios beyond the German experience.

Results

For parameter values compatible with the German experience, where MMRV (Priorix-Tetra™, GSK, Belgium) was introduced in 2006, the model predicted that transitioning from MMR + V to MMRV would induce 225 vaccine-related FC hospitalisation days whilst preventing 1976 varicella-related hospitalisation days per year. The HR estimated by Monte Carlo simulations was 8.5 (95 % confidence interval: 1.99–25.22). A sensitivity analysis on two key parameters suggested that transitioning from MMR + V to MMRV would be favourable in situations where MMRV use would significantly impact varicella vaccination uptake.

Conclusions

MMRV use instead of MMR + V can substantially reduce the number of hospitalisation days, despite increased FC risk when MMRV is used as a first dose of measles-containing vaccine.

Varicella zoster virus related deaths and hospitalizations before the introduction of universal vaccination with the tetraviral vaccine

OBJECTIVE

To characterize varicella zoster virus-related deaths and hospitalizations in Brazil before universal vaccination with the tetravalent (measles, mumps, rubella, and varicella) vaccine, attempting to collect baseline data on varicella morbidity and mortality in order to evaluate the impact of the varicella vaccination program.

METHODS

Varicella-associated mortality data were evaluated between 1996 and 2011 and varicella zoster virus-associated hospitalizations between 1998 and 2013. Data were gathered from the Informatics Department of the Unified Health System, considering the International Classification of Diseases, 10th Revision, code B01. All age groups were assessed. Varicella-specific mortality rates were calculated and seasonality of varicella-zoster virus-associated hospitalizations was described.

RESULTS

There were 2334 varicella deaths between 1996 and 2011, 19.3% in infants aged less than 1 year and 36% in children from 1 to 4 years. In infants under 1 year, varicella mortality rates reached 3.2/100,000/year. In children aged 1-4 years, varicella mortality rates reach 1.64/100,000/year. Average annual mortality rates for varicella in Brazil are 0.88/100,000 in infants under 1 year and 0.40/100,000 in children aged 1-4 years. The total number of hospitalizations associated with varicella zoster virus was 62,246 from 2008 to 2013. Varicella-associated hospitalizations have a seasonal distribution in children, peaking in November. In the elderly, monthly averages of herpes zoster-associated hospitalizations present no significant seasonal variation.

CONCLUSIONS

Varicella is associated, in the pre-vaccine period, to significant morbidity and mortality in Brazil. The universal vaccination program is expected to decrease the disease burden from varicella.

Digital epidemiology reveals global childhood disease seasonality and the effects of immunization

Public health surveillance systems are important for tracking disease dynamics. In recent years, social and real-time digital data sources have provided new means of studying disease transmission. Such affordable and accessible data have the potential to offer new insights into disease epidemiology at national and international scales. We used the extensive information repository Google Trends to examine the digital epidemiology of a common childhood disease, chicken pox, caused by varicella zoster virus (VZV), over an 11-y period. We (i) report robust seasonal information-seeking behavior for chicken pox using Google data from 36 countries, (ii) validate Google data using clinical chicken pox cases, (iii) demonstrate that Google data can be used to identify recurrent seasonal outbreaks and forecast their magnitude and seasonal timing, and (iv) reveal that VZV immunization significantly dampened seasonal cycles in information-seeking behavior. Our findings provide strong evidence that VZV transmission is seasonal and that seasonal peaks show remarkable latitudinal variation. We attribute the dampened seasonal cycles in chicken pox information-seeking behavior to VZV vaccine-induced reduction of seasonal transmission. These data and the methodological approaches provide a way to track the global burden of childhood disease and illustrate population-level effects of immunization. The global latitudinal patterns in outbreak seasonality could direct future studies of environmental and physiological drivers of disease transmission.

Global Varicella Vaccine Effectiveness: A Meta-analysis

CONTEXT

Several varicella vaccines are available worldwide. Countries with a varicella vaccination program use 1- or 2-dose schedules.

OBJECTIVE

We examined postlicensure estimates of varicella vaccine effectiveness (VE) among healthy children.

DATA SOURCES

Systematic review and descriptive and meta-analysis of Medline, Embase, Cochrane libraries, and CINAHL databases for reports published during 1995-2014.

STUDY SELECTION

Publications that reported original data on dose-specific varicella VE among immunocompetent children.

DATA EXTRACTION

We used random effects meta-analysis models to obtain pooled one dose VE estimates by disease severity (all varicella and moderate/severe varicella). Within each severity category, we assessed pooled VE by vaccine and by study design. We used descriptive statistics to summarize 1-dose VE against severe disease. For 2-dose VE, we calculated pooled estimates against all varicella and by study design.

RESULTS

The pooled 1-dose VE was 81% (95% confidence interval [CI]: 78%-84%) against all varicella and 98% (95% CI: 97%-99%) against moderate/severe varicella with no significant association between VE and vaccine type or study design (P > .1). For 1 dose, median VE for prevention of severe disease was 100% (mean = 99.4%). The pooled 2-dose VE against all varicella was 92% (95% CI: 88%-95%), with similar estimates by study design.

LIMITATIONS

VE was assessed primarily during outbreak investigations and using clinically diagnosed varicella.

CONCLUSIONS

One dose of varicella vaccine was moderately effective in preventing all varicella and highly effective in preventing moderate/severe varicella, with no differences by vaccine. The second dose adds improved protection against all varicella.

Varicella vaccine without human serum albumin versus licensed varicella vaccine in children during the second year of life: a randomized, double-blind, non-inferiority trial

Background

GSK’s varicella vaccine contains human serum albumin (HSA) which is used to stabilize the virus and prevent immunogens from adhering to the injection vial walls. However, because HSA is derived from human blood, there is a theoretical risk that it might contain infectious agents which could be unsafe for humans. Given this concern, a study was undertaken to compare the immunogenicity and safety of a new formulation without HSA with the currently licensed varicella vaccine in the Czech Republic and Hungary.

Methods

Healthy children aged 11–21 months received two doses of the varicella vaccine either with or without HSA. Antibody titres against varicella-zoster virus (anti-VZV) were measured 42 days after each dose, using an immunofluorescence assay (IFA, cut-off = 4dilution⁻¹) and enzyme linked immunosorbent assay (ELISA, cut-off = 25 mIU/ml). Solicited local symptoms were recorded during a 4-day post-vaccination follow-up period; solicited general and unsolicited symptoms were recorded during a 43-day post-vaccination follow-up period and serious adverse event (SAEs) were recorded throughout the study.

Results

Of 244 children (mean age = 15.2 months [SD = 3.2]) vaccinated in the study, 233 (vaccine without HSA N = 117; vaccine containing HSA N = 116) formed the according-to-protocol immunogenicity cohort. Observed seroconversion/seroresponse rates were >98 and 100 %, 42 days after doses 1 and 2, respectively. The rates were within the same range in both groups, irrespective of the testing assay. The varicella vaccine without HSA was non-inferior to the licensed vaccine in terms of anti-VZV antibody Geometric Mean Titre/Concentration ratio (1.12 [95 % CI:0.86–1.46] by IFA; 1.12 [95 % CI:0.93–1.33] by ELISA) approximately six weeks after the first dose of the 2-dose vaccination course. The incidence of solicited and unsolicited symptoms was similar after both vaccines; low-grade fever was numerically higher after the first dose of the varicella vaccine without HSA. Seven SAEs were reported, none of which were fatal or considered to be vaccine-related.

Conclusions

The first dose of a new varicella vaccine without HSA was immunologically non-inferior to the licensed varicella vaccine. After two doses, both vaccines had acceptable safety profiles in children aged 11–21 months in the Czech Republic and Hungary.

Trial registration

NCT00568334, registered on 5 December 2007 (www.clinicaltrials.gov).

Burden of varicella in Italy, 2001-2010: analysis of data from multiple sources and assessment of universal vaccination impact in three pilot regions

Varicella represents the most widespread vaccine-preventable childhood infectious disease in Italy. The purpose of this retrospective study was to assess the burden of varicella in Italy and in three regions that first implemented universal varicella vaccination. Four data sources were analysed: statutory notification data, the National Hospital Discharge Database, mortality data, and the vaccination coverage reached in Sicilia, Veneto and Apulia. The incidence rates per 100,000 population were calculated using the Italian resident population provided by the Italian Institute of Statistics in 2001-2010. In 2001-2010, the mean annual incidence of notifications of varicella was 150.7 cases per 100,000 population, reaching 948.6 cases per 100,000 population in the paediatric age group. The annual incidence declined to 102.6 per 100,000 population in 2010. During the period considered, 20,295 hospitalizations for varicella were observed. The mean annual incidence was 3.4 per 100,000 population, reaching a minimum of 2.5 per 100,000 in 2009 and 2010. Of the hospitalizations, 68.4% occurred in the paediatric age group. The median length of hospital stay was 4 days. During 2001-2003 and 2006-2010, 33 deaths were reported. In the three regions considered, vaccination coverage increased steadily, reaching 81.5% in Sicily, 79.4% in Veneto and 75.6% in Apulia in 2010. During the same period, hospitalization and notification rates decreased significantly. This study demonstrated that varicella continues to represent a relevant health problem in Italy, especially in the paediatric age group. Data obtained from the three Italian regions that first introduced universal vaccination demonstrated that vaccination reduces the incidence of varicella and hospitalization rates.

Effectiveness of vaccination against varicella in children under 5 years in Puglia, Italy 2006-2012

In Italy, between 2003 and 2010, 8/21 Regions recommended varicella routine vaccination (URV). The National Immunization Plan (PNPV) 2012-2014 scheduled the introduction of URV nationwide in 2015, following the results achieved by the eight Regions.   Puglia adopted varicella URV in 2006. This study describes epidemiology and costs of varicella in Puglia between 2003 and 2012. One-dose Vaccine Effectiveness (VE) against varicella of any severity and severe hospitalized cases in children was also evaluated. Vaccination coverage (VC) was estimated from the regional immunization registry. Incidence and hospitalization rates were calculated from computerised surveillance system for communicable diseases and hospital discharge registry (ICD9-CM codes: 052.x), respectively. URV impact was assessed by Incidence Rate Ratios (IIRs) and Hospitalization Risk Ratios (HRRs). Hospitalization costs were also evaluated. VE was estimated using the screening method, where PPV was VC in children aged &lt;72 months and PCV was the proportion of cases vaccinated among notified or hospitalized cases, respectively. One-dose VC in children aged ≤ 24 months increased from 49% in the birth cohort 2006 to 91.1% in the cohort 2010; 2-dose VC was 64.8% and 28.8% in the 2005 and 1997 cohort, respectively. Comparing pre and post-vaccination era, incidence declined from 122.5 ×100 000 in 2003-2005 to 13.7 in 2009-2012 (IRR = 0.11, 95% CI = 0.10-0.12), hospitalization rate from 3.9 ×100 000 to 1.1 (HRR = 0.29, 95% CI = 0.21-0.4), hospitalization costs from 319 000 Euros/year to 106 000. One-dose VE against varicella of any severity and severe hospitalized disease was 98.8% and 99%, respectively. Our findings strongly support varicella URV introduction into the Italian Essential Health Interventions, as scheduled by 2015.

Varicella vaccination programs do not seem to shift the age of disease to older age groups

The paper of Baxter et al., recently published in Pediatrics show through five cross-sectional studies, a high impact of vaccination in the decline of varicella incidence and hospitalizations in all age groups in the United States between 1995 and 2009. As a consequence of herd immunity, varicella incidence has also diminished in those non vaccinated, which indicates no shift in the burden of varicella to older age groups.

Successes and challenges in varicella vaccine

Varicella is a highly contagious disease caused by primary infection with varicella zoster virus (VZV). VZV infection, as well as varicella vaccination, induces VZV-specific antibody and T-cell-mediated immunity, essential for recovery. The immune responses developed contribute to protection following re-exposure to VZV. When cell-mediated immunity declines, as occurs with aging or immunosuppression, reactivation of VZV leads to herpes zoster (HZ). It has been almost 20 years since universal varicella vaccination has been implemented in many areas around the globe and this has resulted in a significant reduction of varicella-associated disease burden. Successes are reviewed here, whilst emphasis is put on the challenges ahead. Most countries that have not implemented routine childhood varicella vaccination have chosen to vaccinate high-risk groups alone. The main reasons for not introducing universal vaccination are discussed, including fear of age shift of peak incidence age and of HZ incidence increase. Possible reasons for not observing the predicted increase in HZ incidence are explored. The advantages and disadvantages of universal vs targeted vaccination as well as different vaccination schedules are discussed.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

The prevention of varicella (chickenpox) using live attenuated varicella vaccines has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States and Australia. Many countries do not routinely immunise children against varicella and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH METHODS

We searched CENTRAL (2014, Issue 1), MEDLINE (1966 to March week 1, 2014), EMBASE (January 1990 to March 2014) and LILACS (1982 to March 2014). We searched for unpublished trials registered on the clinicaltrials.gov and WHO ICTRP websites.

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse events following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

We identified three trials involving 110 healthy children who were siblings of household contacts. The included trials varied in study quality, vaccine used, length of follow-up and outcomes measured and, as such, were not suitable for meta-analysis. We identified high or unclear risk of bias in two of the three included studies. Overall, 13 out of 56 vaccine recipients (23%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with fewer than 50 skin lesions). In the three trials, most participants received PEP within three days following exposure; too few participants were vaccinated four to five days post-exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included trial reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. We identified no RCTs for adolescents or adults. Safety was not adequately addressed.

Protection against varicella with two doses of combined measles-mumps-rubella-varicella vaccine versus one dose of monovalent varicella vaccine: a multicentre, observer-blind, randomised, controlled trial

BACKGROUND

Rates of varicella have decreased substantially in countries implementing routine varicella vaccination. Immunisation is possible with monovalent varicella vaccine or a combined measles-mumps-rubella-varicella vaccine (MMRV). We assessed protection against varicella in naive children administered one dose of varicella vaccine or two doses of MMRV.

METHODS

This study was done in ten European countries with endemic varicella. Healthy children aged 12-22 months were randomised (3:3:1 ratio, by computer-generated randomisation list, with block size seven) to receive 42 days apart (1) two doses of MMRV (MMRV group), or (2) MMR at dose one and monovalent varicella vaccine at dose two (MMR+V group), or (3) two doses of MMR (MMR group; control). Participants and their parents or guardians, individuals involved in assessment of any outcome, and sponsor staff involved in review or analysis of data were masked to treatment assignment. The primary efficacy endpoint was occurrence of confirmed varicella (by detection of varicella zoster virus DNA or epidemiological link) from 42 days after the second vaccine dose to the end of the first phase of the trial. Cases were graded for severity. Efficacy analyses were per protocol. Safety analyses included all participants who received at least one vaccine dose. This trial is registered with ClinicalTrials.gov, number NCT00226499.

FINDINGS

Between Sept 1, 2005, and May 10, 2006, 5803 children (mean age 14·2 months, SD 2·5) were vaccinated. In the efficacy cohort of 5285 children, the mean duration of follow-up in the MMRV group was 36 months (SD 8·8), in the MMR+V group was 36 months (8·5) and in the MMR group was 35 months (8·9). Varicella cases were confirmed for 37 participants in the MMRV group (two moderate to severe), 243 in the MMR+V group, and 201 in the MMR group. Second cases occurred for three participants (all in the MMR+V group). Varicella cases were moderate to severe for two participants in the MMRV group, 37 in the MMR+V group (one being a second case that followed a mild first case); and 117 in the MMR group. Efficacy of two-dose MMRV against all varicella was 94·9% (97·5% CI 92·4-96·6), and against moderate to severe varicella was 99·5% (97·5-99·9). Efficacy of one-dose varicella vaccine against all varicella was 65·4% (57·2-72·1), and against moderate to severe varicella (post hoc) was 90·7% (85·9-93·9). The most common adverse event in all groups was injection-site redness (up to 25% of participants). Within 15 days after dose one, 57·4% (95% CI 53·9-60·9) of participants in the MMRV group reported fever of 38°C or more, by contrast with 44·5% (41·0-48·1) with MMR+V, and 39·8% (33·8-46·1) with MMR. Eight serious adverse events were deemed related to vaccination (three MMRV, four MMR+V, one MMR). All resolved within the study period.

INTERPRETATION

These results support the implementation of two-dose varicella vaccination on a short course, to ensure optimum protection from all forms of varicella disease.

FUNDING

GlaxoSmithKline Vaccines.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Seroprevalences of varicella-zoster virus, herpes simplex virus and cytomegalovirus in a cross-sectional study in Mexico

We estimated the seroprevalences of varicella-zoster virus (VZV), herpes simplex virus (HSV) and cytomegalovirus (CMV) in this cross-sectional database study. Serum samples collected during the National Health and Nutrition survey (ENSANUT 2006) were obtained from subjects aged 1-70 years between January and October 2010. Serological assays for the determination of antibodies against VZV, HSV and CMV were performed. The overall seroprevalences of VZV, HSV-1, HSV-2 and CMV were 85.8%, 80.9%, 9.9% and 89.2%, respectively. Seroprevalences of VZV, HSV-1 and CMV were comparable between males and females. For HSV-2, although the seroprevalence rate was higher in females when compared to males, this difference in seroprevalence was not statistically significant. Seroprevalence rates for VZV, HSV-1, HSV-2 and CMV increased with age (p-value<.0001). Differences in seroprevalence rate for VZV by socioeconomic status (SES) were significant (p-value<0001). Results of the serological analyses reported high VZV seroprevalence, indicating high transmission in the Mexican population with children and adolescents at risk of acquiring VZV. Global HSV-1 seroprevalence was high, especially in adults. HSV-1 and HSV-2 seroprevalences were consistently higher in women than men, particularly for HSV-2. CMV seroprevalence was higher in Mexico when compared to developed countries. Seroepidemiological data on VZV supports the fact that varicella vaccination may serve as an alternative effective solution to reduce transmission in the Mexican population. For CMV and HSV, since no vaccines are available, activities to reduce transmission are important to reduce the risk of complications and therefore need to be considered.

The effectiveness of varicella vaccination in children in Germany: a case-control study

BACKGROUND

Effectiveness of 1 dose of varicella vaccination was estimated to be 85-88% against clinical varicella of any severity in case-control studies in non-European countries, but lower effectiveness has been demonstrated in outbreaks.

METHODS

A prospective, age- and practice-matched case-control study was conducted in Germany to assess the effectiveness of 1 dose of OKA/GSK varicella vaccine (derived from the OKA strain, a Japanese clinical isolate) and of any varicella vaccine (including OKA/GSK, OKA/Merck and MMR-OKA/GSK) against polymerase chain reaction (PCR)-confirmed varicella under conditions of routine use.

RESULTS

The cohort included 432 PCR-confirmed cases and 432 matched controls (1-7 years old). Varicella vaccination was reported for 13.2% (57/432) of cases and 45.1% (195/432) of controls. Median time since vaccination was 28 and 25 months, respectively. Vaccinated cases experienced milder disease (P < 0.0001) and shorter duration of disease (P = 0.004) compared with unvaccinated cases. After adjusting for gender and school/day-care attendance, vaccine effectiveness of 1 dose of OKA/GSK against PCR-confirmed varicella of any severity was 71.5% (95% confidence interval [CI]: 49.1-84.0) and 94.7% (95% CI: 77.8-98.7) against PCR-confirmed moderate or severe varicella. Adjusted effectiveness for any varicella vaccine was 86.4% (95% CI: 77.3-91.8) against any severity and 97.7% (95% CI: 90.5-99.4) against moderate or severe varicella.

CONCLUSIONS

One dose of varicella vaccine provided high protection against moderate and severe varicella disease for a period of up to 5 years after vaccination. However, further effectiveness data are needed to assess long-term protection.

Children Hospitalized for Varicella: Complications and Cost Burden

OBJECTIVE

To evaluate the direct medical cost of hospital admissions for patients with varicella (i.e., chickenpox) to assess the cost burden of varicella from a health care perspective for ultimate use in health economics studies in Turkey.

METHODS

Records of children hospitalized with varicella at the Bakirkoy Maternity and Children's Hospital between November of 2006 and June of 2011 were reviewed. Reasons for hospitalization, types of varicella-associated complications, and direct medical cost of hospitalization were noted. Patients with underlying risk factors were excluded. Data obtained from one hospital were used to estimate the national cost of the disease.

RESULTS

During the 4.5-year study period, 234 patients were hospitalized with varicella. Of these cases, 48 (20%) children previously ill with underlying cancers or chronic diseases were excluded from the study. Ultimately, 186 previously healthy children (age range: 14 days to 159 months, median age: 14 months) were included. The main reasons for hospitalization were complications related to varicella (79%), the most frequent of which was skin and soft tissue infections, followed by neurological complications and pneumonia. The median cost of hospitalization per patient was US $283, 50% of which was attributed to medication costs. The annual cost for varicella hospitalizations in Turkey was estimated at US $396,200.

CONCLUSIONS

A significant number of healthy children are hospitalized for varicella and associated complications. Descriptions of these complications and their related costs provide important data for cost-effectiveness studies for decisions about the inclusion of the varicella vaccine in a childhood vaccination program.

Varicella routine vaccination and the effects on varicella epidemiology - results from the Bavarian Varicella Surveillance Project (BaVariPro), 2006-2011

BACKGROUND

In 2004, routine varicella vaccination was recommended in Germany for children 11-14 months of age with one dose, and since 2009, with a second dose at 15-23 months of age. The effects on varicella epidemiology were investigated.

METHODS

Data on varicella vaccinations, cases and complications were collected from annual parent surveys (2006-2011), monthly paediatric practice surveillance (Oct 2006 - Sep 2011; five varicella seasons) and paediatric hospital databases (2005-2009) in the area of Munich (about 238,000 paediatric inhabitants); annual incidences of cases and hospitalisations were estimated.

RESULTS

Varicella vaccination coverage (1st dose) in children 18-36 months of age increased in two steps (38%, 51%, 53%, 53%, 66% and 68%); second-dose coverage reached 59% in the 2011 survey. A monthly mean of 82 (62%) practices participated; they applied a total of 50,059 first-dose and 40,541 second-dose varicella vaccinations, with preferential use of combined MMR-varicella vaccine after recommendation of two doses, and reported a total of 16,054 varicella cases <17 years of age. The mean number of cases decreased by 67% in two steps, from 6.6 (95%CI 6.1-7.0) per 1,000 patient contacts in season 2006/07 to 4.2 (95%CI 3.9-4.6) in 2007/08 and 4.0 (95%CI 3.6-4.3) in 2008/09, and further to 2.3 (95%CI 2.0-2.6) in 2009/10 and 2.2 (95%CI 1.9-2.5) in 2010/11. The decrease occurred in all paediatric age groups, indicating herd protection effects. Incidence of varicella was estimated as 78/1,000 children <17 years of age in 2006/07, and 19/1,000 in 2010/11. Vaccinated cases increased from 0.3 (95%0.2-0.3) per 1,000 patient contacts in 2006/07 to 0.4 (95%CI 0.3-0.5) until 2008/09 and decreased to 0.2 (95%CI 0.2-0.3) until 2010/11. The practices treated a total of 134 complicated cases, mainly with skin complications. The paediatric hospitals recorded a total of 178 varicella patients, including 40 (22.5%) with neurological complications and one (0.6%) fatality due to varicella pneumonia. Incidence of hospitalisations decreased from 7.6 per 100,000 children <17 years of age in 2005 to 4.3 in 2009, and from 21.0 to 4.7 in children <5 years of age.

CONCLUSIONS

Overall, the results show increasing acceptance and a strong impact of the varicella vaccination program, even with still suboptimal vaccination coverage.

Primary versus secondary failure after varicella vaccination: implications for interval between 2 doses

BACKGROUND

Two-dose varicella vaccination is recommended for optimal control of varicella in populations with high (>90%) 1-dose coverage. Optimal timing of the second dose may depend on whether breakthrough varicella results from primary vaccine failure (no protective immunity after vaccination) or secondary vaccine failure (waning protective immunity).

METHODS

Published literature (1995 to 2012) on vaccine failure after varicella vaccination cited in PubMed and other online sources was reviewed.

RESULTS

Nineteen publications detailed 21 varicella outbreaks with breakthrough varicella rates ranging from 0% to 42%; the publications showed no consistent trend between breakthrough varicella rate and time since vaccination.

CONCLUSIONS

Literature to date indicates a relatively high rate of primary vaccine failure and limited evidence of secondary vaccine failure among 1-dose varicella vaccine recipients, suggesting that a short interval between 2 doses might be preferable in countries considering implementation of universal varicella vaccination to reduce breakthrough varicella. However, any potential disruption to well-established vaccination schedules should be considered.