Impact assessment of immunization and the COVID-19 pandemic on varicella across Europe using digital epidemiology methods: A descriptive study.

BACKGROUND: Varicella is usually a mild disease in children but may be life-threatening, especially in adolescents and adults. Infection control measures implemented during the Coronavirus Disease 2019 (COVID-19) pandemic may have suppressed varicella transmission, potentially creating an 'immunity debt', particularly in countries without universal varicella vaccination. OBJECTIVES: To assess trends in Google search engine queries for varicella keywords as a proxy for varicella infection rates and to evaluate the effect of universal varicella vaccination on these trends. A further objective was to assess the impact of the COVID-19 pandemic on varicella keyword search query trends in countries with and without universal varicella vaccination. METHODS: This study used the keyword research tool, Google Trends, to evaluate trends in time series of the relative search query popularity of language-specific varicella keywords in 28 European countries from January 2015 through December 2021. The Google Ads Keyword Planner tool was used to evaluate absolute search volumes from March 2018 through December 2021. RESULTS: The relative search query popularity of varicella keywords displayed marked seasonal variation. In all 28 countries, the relative search query popularity of varicella keywords declined after the start of the COVID-19 pandemic (March 2020), compared with pre-pandemic levels (range, -18% to -70%). From April 2020 to July 2021, a period of intense COVID-19 transmission and infection control, absolute search volumes for varicella keywords were lower than pre-pandemic levels but rebounded after July 2021, when infection control measures were relaxed. CONCLUSION: This evaluation of search query trends demonstrated that search query data could be used as a proxy for trends in varicella infection rates and revealed that transmission of varicella may have been suppressed during the COVID-19 pandemic. Consideration should be given to using search query data to better understand the burden of varicella, particularly in countries where surveillance systems are inadequate.

Prospective study of loss of health-related quality adjusted life years in children and their families due to uncomplicated and hospitalised varicella.

INTRODUCTION AND AIMS: Although usually benign, varicella can lead to serious complications and sometimes long-term sequelae. Vaccines are safe and effective but not yet included in immunisation programmes in many countries. We aimed to quantify the impact on health-related quality of life (HRQoL) in terms of quality-adjusted life years (QALY) in children with varicella and their families, key to assessing cost-utility in countries with low mortality due to this infection. METHODS: Children with varicella in the community and admitted to hospitals in Portugal were included over 18 months from January 2019. Children's and carers' HRQoL losses were assessed prospectively using standard multi-attribute utility instruments for measuring HRQoL (EQ-5D and CHU9D), from presentation to recovery, allowing the calculation of QALYs. RESULTS: Among 109 families with children with varicella recruited from attendees at a pediatric emergency service (community arm), the mean HRQoL loss/child was 2.0 days (95 % CI 1.9-2.2, n = 101) (mean 5.4 QALYs/1000 children (95 % CI 5.3-6.1) and 1.3 days/primary carer (95 % CI 1.2-1.6, n = 103) (mean 3.6 QALYs /1000 carers (95 % CI 3.4-4.4). Among 114 families with children admitted to hospital because of severe varicella or a complication (hospital arm), the mean HRQoL loss/child was 9.8 days (95 % CI 9.4-10.6, n = 114) (mean 26.8 QALYs /1000 children (95 % CI 25.8-29.0) and 8.5 days/primary carer (95 % CI 7.4-9.6, n = 114) (mean 23.4 QALYs/1000 carers (95 % CI 20.3-26.2). Mean QALY losses/1000 patients were particularly high for bone and joint infections [67.5 (95 % CI 43.9-97.6)]. Estimates for children's QALYs lost using the CHU9D tool were well correlated with those obtained using EQ-5D, but substantially lower. CONCLUSIONS: The impact of varicella on HRQoL is substantial. We report the first measurements of QALYs lost in hospitalised children and in the families of children both in the community and admitted to hospital, providing important information to guide vaccination policy recommendations.

Epidemiology of hospitalisations due to chickenpox and quality of life lost in community and hospital settings: protocol for a prospective cohort study across two countries.

INTRODUCTION: While still a ubiquitous disease of childhood, chickenpox has been effectively controlled in many countries through the use of vaccination. Previous health economic assessment of the use of these vaccines in the UK were based on limited quality of life data and only routinely collected epidemiological outcomes. METHODS AND ANALYSIS: This two armed study will carry prospective surveillance of hospital admissions and recruit from community settings to measure the acute quality of life loss caused by paediatric chickenpox both in the UK and in Portugal. The quality of life effects on children and their primary and secondary caregivers will be assessed using the EuroQol EQ-5D with the Child Health Utility instrument (CHU-9) in addition for children. Results will be used to derive quality-adjusted life year loss estimates for cases of simple varicella and the secondary complications. ETHICS AND DISSEMINATION: We have received National Health Service ethical approval (REC ref: 18/ES/0040) for the inpatient arm, university ethical approval (University of Bristol ref: 60721) for the community arm and 10 sites currently are recruiting in the UK and 14 in Portugal. Informed consent is obtained from the parent(s). Results will be disseminated in peer-reviewed publications. TRIAL REGISTRATION NUMBER: ISRCTN15017985.

Chickenpox in Poland in 2020.

INTRODUCTION: 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. OBJECTIVES: 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. MATERIAL AND METHODS: 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. RESULTS: 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 Swietokrzyskie 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. CONCLUSIONS: 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).

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.

Varicella outbreaks in schools and kindergartens in Shanghai, China from 2011 to 2020.

BACKGROUND: Varicella is a contagious disease caused by varicella-zoster virus and varicella vaccine (VarV) is the most effective way to prevent and control varicella. Despite high VarV coverage there were still varicella outbreaks in schools and kindergartens. We aim to analyze the epidemiological characteristics of varicella outbreaks in Huangpu District, Shanghai, China from 2011 to 2020. METHODS: For varicella outbreaks, case information and vaccination history were collected. Mann-Kendall test and descriptive methods were used to analyzed the trend and epidemiological catachrestic of varicella outbreaks. RESULTS: A total of 57 varicella outbreaks were reported from 2011 to 2020, including 30 outbreaks (52.6%) in primary schools. The results of the Mann-Kendall trend test (z = 1.97, p = 0.049) showed an upward trend in the number of cases during the study period, but the trend change was not statistically significant. Emergency vaccination was carried out in 42 (73.7%) outbreaks which influenced the duration of the epidemic (F = 4.53, p = 0.0379). A total of 573 varicella cases were reported, including 357 cases (62.3%) who had received at least one dose of varicella vaccine. CONCLUSIONS: The number of varicella outbreaks has not changed significantly in the decade from 2011 to 2020. The strategy of varicella vaccination, the development and application of varicella vaccine, and the control measures after the occurrence of varicella outbreaks need to be optimized. In addition to vaccination, as a disease transmitted by contact, quarantine measures, good personal hygiene, environmental disinfection, and ventilation are also important.

Transmission dynamics of varicella before, during and after the COVID-19 pandemic in Japan: a modelling study.

Public health and social measures (PHSMs) targeting the coronavirus disease 2019 (COVID-19) pandemic have potentially affected the epidemiological dynamics of endemic infectious diseases. In this study, we investigated the impact of PHSMs for COVID-19, with a particular focus on varicella dynamics in Japan. We adopted the susceptible-infectious-recovered type of mathematical model to reconstruct the epidemiological dynamics of varicella from Jan. 2010 to Sep. 2021. We analyzed epidemiological and demographic data and estimated the within-year and multi-year component of the force of infection and the biases associated with reporting and ascertainment in three periods: pre-vaccination (Jan. 2010-Dec. 2014), pre-pandemic vaccination (Jan. 2015-Mar. 2020) and during the COVID-19 pandemic (Apr. 2020-Sep. 2021). By using the estimated parameter values, we reconstructed and predicted the varicella dynamics from 2010 to 2027. Although the varicella incidence dropped drastically during the COVID-19 pandemic, the change in susceptible dynamics was minimal; the number of susceptible individuals was almost stable. Our prediction showed that the risk of a major outbreak in the post-pandemic era may be relatively small. However, uncertainties, including age-related susceptibility and travel-related cases, exist and careful monitoring would be required to prepare for future varicella outbreaks.

Pediatric Hospitalization for Varicella in an Italian Pediatric Hospital: How Much Does It Cost?

BACKGROUND: Varicella is a common pediatric infection. Even if it generally has a benign course, it may complicate and require hospitalization. The aim of our study was to estimate the acute hospitalization cost (AHC) for varicella in the acute phase in a pediatric population. METHODS: We calculated the AHC of pediatric patients admitted for varicella at Bambino Gesù Children Hospital, Rome, Italy, from 1 November 2005 to 1 November 2020. RESULTS: In the study period, 825 pediatric patients affected by varicella were hospitalized. The mean hospitalization cost was EUR 4015.35 (range from EUR 558.44 to EUR 42,608.00). Among patients, 55% were unvaccinable due to either their age or their immunosuppression status. They would benefit from herd immunity, reducing the overall AHC by EUR 182,196,506. Since the introduction of the compulsory vaccination against varicella in Italy, we observed a significant reduction in AHC cost of 60.6% in 2019 and of 93.5% in 2020. Finally, from the beginning of the COVID-19 pandemic, we documented a decline of 81.2% and 76.9% in varicella hospitalization, compared to 2018 and 2019, respectively. CONCLUSIONS: Varicella AHC is an important economic and health assessment point and can be useful for improving preventive strategies.

Common communicable diseases in the general population in France during the COVID-19 pandemic.

In France, social distancing measures have been adopted to contain the spread of COVID-19, culminating in national Lockdowns. The use of hand washing, hydro-alcoholic rubs and mask-wearing also increased over time. As these measures are likely to impact the transmission of many communicable diseases, we studied the changes in common infectious diseases incidence in France during the first year of COVID-19 circulation. We examined the weekly incidence of acute gastroenteritis, chickenpox, acute respiratory infections and bronchiolitis reported in general practitioner networks since January 2016. We obtained search engine query volume for French terms related to these diseases and sales data for relevant drugs over the same period. A periodic regression model was fit to disease incidence, drug sales and search query volume before the COVID-19 period and extrapolated afterwards. We compared the expected values with observations made in 2020. During the first lockdown period, incidence dropped by 67% for gastroenteritis, by 79% for bronchiolitis, by 49% for acute respiratory infection and 90% for chickenpox compared to the past years. Reductions with respect to the expected incidence reflected the strength of implemented measures. Incidence in children was impacted the most. Reduction in primary care consultations dropped during a short period at the beginning of the first lockdown period but remained more than 95% of the expected value afterwards. In primary care, the large decrease in reported gastroenteritis, chickenpox or bronchiolitis observed during the period where many barrier measures were implemented imply that the circulation of common viruses was reduced and informs on the overall effect of these measures.

Impact of a two-dose varicella immunization program on the incidence of varicella: a multi-year observational study in Shanghai, China.

BACKGROUND: It remains hesitant to include a two-dose varicella vaccine (VarV) in a national routine immunization program in China. We aimed to quantify the impact of the two-dose VarV on varicella incidence in Shanghai. RESEARCH DESIGN AND METHODS: We directly extracted the data of varicella cases and VarV doses in 2013-2020 in Shanghai, and then estimated the effects of two-dose VarV using a Serfling model. RESULTS: A two-dose VarV immunization program has been extensively implemented since October 2017 and become free since August 2018 in Shanghai. Before and after this program, varicella cases significantly declined in children (P < 0.01), whereas did not in adults aged >18 years (P = 0.22). Compared to the predicted number of varicella cases, actual number was significantly lower by 8% in 2018 and 28% in 2019. Among children aged 4-6 years, the reduction in varicella cases was largest. Moreover, there was a significant reduction in varicella cases throughout 2020 (P < 0.001), in which the decrease due to social distancing for the COVID-19 was 54%. CONCLUSIONS: A two-dose VarV immunization program may further reduce approximately one-third of varicella cases in Shanghai. Children <4 years and adults benefit less in this program, which warrants enhancing the immunization.