Declining incidence of chickenpox in the absence of universal childhood immunisation

Estimation of the burden of varicella in Europe before the introduction of universal childhood immunization

BACKGROUND

Varicella is generally considered a mild disease. Disease burden is not well known and country-level estimation is challenging. As varicella disease is not notifiable, notification criteria and rates vary between countries. In general, existing surveillance systems do not capture cases that do not seek medical care, and most are affected by underreporting and underascertainment. We aimed to estimate the overall varicella disease burden in Europe to provide critical information to support decision-making regarding varicella vaccination.

METHODS

We conducted a systematic literature review to identify all available epidemiological data on varicella IgG antibody seroprevalence, primary care and hospitalisation incidence, and mortality. We then developed methods to estimate age-specific varicella incidence and annual number of cases by different levels of severity (cases in the community, health care seekers in primary care and hospitals, and deaths) for all countries belonging to the European Medicines Agency (EMA) region and Switzerland.

RESULTS

In the absence of universal varicella immunization, the burden of varicella would be substantial with a total of 5.5 million (95% CI: 4.7-6.4) varicella cases occurring annually across Europe. Variation exists between countries but overall the majority of cases (3 million; 95% CI: 2.7-3.3) would occur in children <5 years. Annually, 3-3.9 million patients would consult a primary care physician, 18,200-23,500 patients would be hospitalised, and 80 varicella-related deaths would occur (95% CI: 19-822).

CONCLUSIONS

Varicella disease burden is substantial. Most cases occur in children <5 years old but adults require hospitalisation more often and are at higher risk of death. This information should be considered when planning and evaluating varicella control strategies. A better understanding of the driving factors of country-specific differences in varicella transmission and health care utilization is needed. Improving and standardizing varicella surveillance in Europe, as initiated by the European Centre for Disease Prevention and Control (ECDC), is important to improve data quality to facilitate inter-country comparison.

Seasonal variation and trend of chicken pox in the southern region of Saudi Arabia (2007-2012)

INTRODUCTION

Chicken pox is a contagious disease caused by varicella zoster virus. Children are most susceptible to infection. In 1998, the WHO recommended that routine childhood varicella vaccination be considered in countries where the disease is a relatively important public health concern. There are few data on the trends of chicken pox. We aimed to evaluate the trend of chicken pox in Saudi Arabia (KSA) during the period 2007-2012.

MATERIALS AND METHODS

Data were collected by retrospective review of the existing anonymous surveillance records and book registries of chicken pox cases at the preventive medicine department of Armed Forces Hospital of the Southern Region of Saudi Arabia from 2007 to 2012. The collected data included the number, age, and sex of registered cases.

RESULTS

A seasonal pattern was clearly demonstrated, with peak in March and April. There was also a decreasing trend from 2007 to 2012. Most cases occurred in the age group 4-15 years. The number of infected male patients was a little higher compared with female patients. These results indicate success in controlling the disease in the southern region of Saudi Arabia, which may be attributed to the implementation of public health interventions targeted at reducing infectious diseases (such as the introduction of varicella zoster vaccine in 2008).

RECOMMENDATIONS

We recommend that a future study be conducted on the severity of chicken pox infection in adults (hospitalization, complications, and death) and a national survey among adults for the seroprevalence of markers of infection with varicella zoster.

The changing epidemiology of chickenpox in Alberta

BACKGROUND

Varicella vaccine was licensed in Canada in 1998. The province of Alberta introduced a universal publicly funded varicella vaccination program in 2001.

PURPOSE

To describe the epidemiology of non-fatal cases of chickenpox for which publicly funded health services were utilized for the period 1986-2002.

METHODS

We used the records of Alberta's universal, publicly funded health care insurance system to identify cases of chickenpox for the period 1986-2002. The earliest dated utilization of a health service for which there was an ICD9-CM code of 052.xx or an IC10-CA code of B01.xx was used as the date of illness onset. Denominators for rates were estimated using mid-year population estimates from the Alberta Health Care Insurance Registry. Age-specific rates were estimated for each year.

RESULTS

The crude incidence of chickenpox significantly declined over the period 1994-2002, most steeply after the year 2000. The incidence of chickenpox varied by age group and year and there was evidence of age-group-year interaction. Among those aged 5-19 years, chickenpox incidence began to decline prior to vaccine licensure in Canada. Among those aged less than one year and those aged 1-4 years, the incidence increased until 1999 when a decline began. Over the period 0.8% of cases were hospitalized.

CONCLUSION

Chickenpox rates began to decline prior to the introduction of the publicly funded vaccination program; however the declines in rates among the youngest age-groups are consistent with a vaccination program effect.