Use of National Health Insurance database to evaluate the impact of public varicella vaccination program on burden of varicella in Taiwan

Burden of varicella in the Asia-Pacific region: a systematic literature review

INTRODUCTION

Varicella is a highly contagious infection that can lead to serious complications, particularly in high-risk groups; however, it is vaccine preventable. Disease awareness and understanding of the disease burden can strongly influence vaccine coverage. This review provides insight into the current epidemiology and the importance of varicella from both public health and economic perspectives across the Asia-Pacific (APAC) region. Areas covered: A systematic literature review was conducted to identify studies on the incidence, seroprevalence, fatality rate and complication rate of varicella. Economic burden studies were also captured. Altogether, 125 studies were identified across the region; these were supplemented by government reports (gray data). Reported vaccine coverage varied from 2.8% to 97%; a key influencing factor was inclusion of the varicella vaccine in national immunization programs. In general, varicella incidence in the unvaccinated population was highest in children ≤5 years old and seroprevalence increased with age. Economic analyses highlighted the cost-saving potential of vaccination programs, especially from a societal perspective. Expert opinion: Varicella-related data varied greatly across the APAC region, highlighting the need to better understand the burden of varicella in this area, and particularly identified the need for better surveillance and reporting.

Parental Attitudes and Factors Associated With Varicella Vaccination in Preschool and Schoolchildren in Hong Kong: A Cross-Sectional Study

This study investigates parental attitudes and factors associated with varicella vaccination among preschool and schoolchildren prior to introduction of the vaccine into Hong Kong's universal Childhood Immunization Program.Fourteen kindergartens and 5 primary schools in Hong Kong were randomly selected in 2013. Parents of the students were invited to answer the self-administered questionnaires. Acquired information included demographic characteristics and socioeconomic statuses of families, children's history of chickenpox infection and vaccination, and reasons for getting children vaccinated. Logistic regression was applied to examine the factors associated with vaccination.From the 3484 completed questionnaires, the calculated rates of varicella infection and vaccination were 20.7% and 69.0%, respectively. Barriers to vaccination included parental uncertainties about vaccine effectiveness, lack of recommendation from the government, and concerns on adverse effects. Overall, 71.8%, 69.0%, and 45.7% of the parents rated family doctors, specialists, and the government, respectively, as very important motivators of vaccination. Higher parental educational level and family income, better perceived knowledge of varicella and chance of infection, discussion with a family doctor, and positive health belief towards vaccination were associated with vaccination (all P < 0.05).The rate of vaccination in Hong Kong was higher than that of some other countries that also did not include the vaccine in their routine immunization programs. More positive parental attitudes, higher socioeconomic status, and discussion with a family doctor are associated with greater vaccination rates. The important roles that health professionals and the government play in promoting varicella vaccination were emphasized.

The incidence of varicella and herpes zoster in Taiwan during a period of increasing varicella vaccine coverage, 2000-2008

The introduction and the widespread use of the varicella vaccine in Taiwan has led to a 75-80% decrease in the incidence of varicella in children. However the vaccine's long-term impact on the incidence of herpes zoster (HZ) has attracted attention. By controlling gender, underlying diseases, and age effects, a Poisson regression was applied on the 2000-2008 chart records of 240 000 randomly selected residents who enrolled in the Universal National Health Insurance. The results show that, as the vaccine coverage in children increases, the incidence of varicella decreases. However, the incidence of HZ increased even before the implementation of the free varicella vaccination programme in 2004, particularly in females. The increase in the incidence of HZ cannot be entirely and directly attributed to the widespread vaccination of children. Continuous monitoring is needed to understand the secular trends in HZ before and after varicella vaccination in Taiwan and in other countries.

An outbreak of varicella among schoolchildren in Taipei

Background

The reported cases with varicella have not decreased and outbreaks of varicella among vaccinated children continue to be reported 9 years after the public vaccination program in Taipei. We investigated an outbreak to determine varicella vaccine coverage and effectiveness.

Methods

An outbreak occurred in an elementary school which located in southern Taipei from April 2007 through May 2007. A retrospect cohort study was performed by using a self-administered questionnaire for parents.

Results

Ten out of sixteen varicella cases were vaccinated. Overall vaccine coverage was 71.2%. The common reasons for not receiving varicella vaccine were that varicella vaccine was unavailable because the student didn't live in Taipei (29.4%) or the children could not be vaccinated due to certain illnesses (23.5%). The sensitivity and specificity of self-reported vaccination status was 0.900 (95% CI: 0.864, 0.935) and 0.611 (95% CI: 0.514, 0.701).

The vaccine effectiveness was 69.3%-100.0% against any disease severity of varicella. Overall vaccine effectiveness against moderate or severe varicella was 85.5%. Attending cram school was associated with the risk of developing the varicella illness (RR: 13.39; 95% CI: 5.38, 33.31). Unvaccinated students tended to show moderate to severe (>50 lesions) afflictions of the disease (RR: 4.17; 95% CI: 1.15, 15.14).

Conclusions

Because of the low vaccination coverage, varicella outbreaks continue to be reported in Taipei. Increasing vaccine coverage and second dose vaccination for increasing vaccine effectiveness may be considered.

The changing epidemiology of varicella incidence after implementation of the one-dose varicella vaccination policy

The varicella vaccine has been available in the Taiwan market since July 1997. Beginning 1998-1999, Taipei City and Taichung City/County as the early launch areas included the varicella vaccine in their free pediatric vaccination programs. By contrast, the national free vaccination program was not implemented until 2004. We aim to investigate the changing epidemiology of varicella incidence through an analysis of age-period-cohort effects. With the greatest decrease in varicella incidence occurring in children aged below 6, the incidence of varicella shifted to older age groups as reflected in different birth cohorts. The current study provides important implications for the current vaccination policy.

Population-based epidemiologic study of Wilson's disease in Taiwan

BACKGROUND

The purpose of the study is to investigate the epidemiology and medical expenses of Wilson's disease in Taiwan.

METHODS

Cases of Wilson's disease were identified from the National Health Insurance Research Database with corresponding International Classification of Diseases, Ninth Revision (ICD-9) code 275.1 from January 2000 to December 2005. Age and sex-specific incidences were estimated by dividing the incidence number by population data obtained from the Department of Statistics, Ministry of the Interior.

RESULTS

During the study period, 495 cases of Wilson's disease were identified. The male to female ratio was 1.28. The average annual incidence rate was 0.27 per 100,000, and the incidence rate peaked in the age group of 15-19 years. Most cases were juvenile and young adults. The prevalence increased steadily during the study period. Cirrhosis of the liver was the most common co-existing condition.

CONCLUSIONS

This is the first population-based epidemiologic study of Wilson's disease in Taiwan. Because of the effective and affordable treatment, the prevalence of Wilson's disease in Taiwan is expected to increase continuously.

Impact of varicella vaccination on health care outcomes in Ontario, Canada: effect of a publicly funded program?

Varicella vaccines have been available for private purchase in Canada since 1998. Ontario introduced publicly funded varicella vaccination in 2004. We assessed the effects of private availability of varicella vaccines and subsequent implementation of a publicly funded vaccination program on varicella-related hospitalizations, emergency department (ED) use, and visits to physicians' offices in Ontario. Rates of hospitalizations, ED use, and office visits decreased 53% (95% CI, 48-58%), 43% (95% CI, 41-44%), and 45% (95% CI, 44-45%) after publicly funded vaccination, compared to only 9% (95% CI, 4-14%), 23% (95% CI, 22-24%), and 29% (95% CI, 28-29%) after private availability. Varicella vaccination is effective at reducing varicella-related health care use, with benefits extending beyond those who receive the vaccine. Publicly funded vaccination programs may be more effective than private vaccine availability.

Evaluation of the National Notifiable Disease Surveillance System in Taiwan: An example of varicella reporting

Despite the mandatory reporting by laws, the incompleteness of notifiable infectious disease reporting is well-documented in many countries for various diseases. The purpose of this study is to investigate the completeness of varicella reporting in Taiwan. Annual reports of National Notifiable Disease Surveillance System in Taiwan were compared to the annual outpatient claims of National Health Insurance (NHI) in the years of 2000, 2001, and 2002. Age and area-specific reporting rates of varicella were calculated by dividing the respective reported cases by the number of incidence cases. The reporting rate was the highest in aged 0 year in all years, followed by the 20-29- and 30-39-year groups. The reporting rate in each age group increased gradually during the study period. Other than Taipei City, the reporting rates in all regions were below 9% during this period. This study suggested that varicella reporting rate is very low in Taiwan. In addition, the reporting rates were inconsistent in 2000-2002, making the estimation of prevalence and vaccine efficacy using data from the National Notifiable Disease Surveillance System almost impossible. This study indicated that the physicians in Taiwan should improve their knowledge and attitude toward notifiable infectious diseases.