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

Abstract

BackgroundVaricella 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.MethodsWe 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.ResultsIn 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).ConclusionsVaricella 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-017-2445-2) contains supplementary material, which is available to authorized users.

Burden of varicella in Central and Eastern Europe: findings from a systematic literature review

“…In a country with no vaccination program, the majority of incident cases (52-78%) occur in children aged under 6 years, rising to 89-96% in those aged under 12 years [1]. A systematic literature review (SLR) examining varicella disease burden across 31 European countries estimated a total of 5.5 million varicella cases annually before the introduction of childhood immunization, including 3 million cases in children aged under 5 years [2]. In Central and Eastern Europe (CEE) in particular, annual incidences of community varicella in children aged under 5 years ranged from 7108 per 100,000 same-age cohort in Romania to 11,640 per 100,000 in Slovenia [2].…”

“…A systematic literature review (SLR) examining varicella disease burden across 31 European countries estimated a total of 5.5 million varicella cases annually before the introduction of childhood immunization, including 3 million cases in children aged under 5 years [2]. In Central and Eastern Europe (CEE) in particular, annual incidences of community varicella in children aged under 5 years ranged from 7108 per 100,000 same-age cohort in Romania to 11,640 per 100,000 in Slovenia [2]. Incidences of varicella-related hospitalizations in CEE were also highest in this age group, ranging from 22-27 per 100,000 children of the same age in Romania to 36-44 per 100,000 in Slovenia [2].…”

The burden of herpes zoster disease in Norway

“…In Europe, an estimated 5.5 million (95% CI: 4.7-6.4) cases of varicella are occurring annually in the absence of universal varicella vaccination [52]. Although, there is a variation of the burden of varicella between the countries the overall majority of the cases (3 million; 95% CI: 2.7-3.3) occur in children <5 years of age [52].…”

“…In Europe, an estimated 5.5 million (95% CI: 4.7-6.4) cases of varicella are occurring annually in the absence of universal varicella vaccination [52]. Although, there is a variation of the burden of varicella between the countries the overall majority of the cases (3 million; 95% CI: 2.7-3.3) occur in children <5 years of age [52]. Pre-vaccine rates of primary health care consultations for varicella in Europe were reported between 281 and 777 cases per 100,000 person-years [53][54][55][56][57][58].…”

Varicella and herpes zoster vaccine development: lessons learned

“…It has a distinct seasonal pattern in temperate climates where the highest incidence occurs in winter and spring [5]. Before the introduction of varicella vaccine, almost universal infection with VZV occurred, with the annual incidence of varicella in many countries corresponding approximately to the birth cohort [20]. There are some geographic differences, for example, infection typically occurs in early childhood in temperate settings such as the USA where more than 90% of people are infected before the age of 15 years [5,21], in contrast to tropical countries where primary VZV infection may be more common among adolescents and adults [9].…”