Abstract
ObjectiveTo describe the impact of varicella vaccination on varicella-related hospitalization rates in countries that implemented universal vaccination against the disease. Data sourceWe identified countries that implemented universal vaccination against varicella at the http://apps.who.int/immunization_monitoring/globalsummary/schedules site of the World Health Organization and selected articles in Pubmed describing the changes (pre/post-vaccination) in the varicella-related hospitalization rates in these countries, using the Keywords “varicella”, “vaccination/vaccine” and “children” (or) “hospitalization”. Publications in English published between January 1995 and May 2015 were included. Data synthesis24 countries with universal vaccination against varicella and 28 articles describing the impact of the vaccine on varicella-associated hospitalizations rates in seven countries were identified. The US had 81.4%–99.2% reduction in hospitalization rates in children younger than four years, 6–14 years after the onset of universal vaccination (1995), with vaccination coverage of 90%; Uruguay: 94% decrease (children aged 1–4 years) in six years, vaccination coverage of 90%; Canada: 93% decrease (age 1–4 years) in 10 years, coverage of 93%; Germany: 62.4% decrease (age 1–4 years) in 8 years, coverage of 78.2%; Australia: 76.8% decrease (age 1–4 years) in 5 years, coverage of 90%; Spain: 83.5% decrease (age <5 years) in four years, coverage of 77.2% and Italy 69.7%–73.8% decrease (general population), coverage of 60%–95%. ConclusionsThe publications showed variations in the percentage of decrease in varicella-related hospitalization rates after universal vaccination in the assessed countries; the results probably depend on the time since the implementation of universal vaccination, differences in the studied age group, hospital admission criteria, vaccination coverage and strategy, which does not allow direct comparison between data.
Highlights
Varicella is caused by a DNA virus of the Herpesviridae family
This study aimed to describe the impact of varicella vaccine (VV) in varicella-related hospitalization rates in countries that have adopted universal vaccination against the disease, in order to predict the impact of this strategy in Brazil for the coming years
In a search conducted in May 2015 on the World Health Organization (WHO) website, it was observed that 24 countries had adopted the VV universally (Table 1): eight in Europe, ten in the Americas, four in the Eastern Mediterranean, and two in the East Pacific.[13]
Summary
Varicella is caused by a DNA virus of the Herpesviridae family. It is highly contagious, with an annual incidence of 26---61 cases per 1000 unvaccinated individuals; it usually has a benign course, but can evolve with complications from the virus itself or from secondary bacterial infections in both immunodeficient patients and immunocompetent individuals.1---4Complications from varicella virus itself are pneumonia, acute obstructive respiratory disease, cerebellitis, encephalitis, meningitis, and other rarer conditions such as neutropenia, thrombocytopenia, Henoch---Schonlein, synovitis, and Reye’s syndrome.[5,6] The complications from secondary bacterial infection include impetigo, abscesses, cellulitis, necrotizing fasciitis, pneumonia, toxic shock syndrome, and sepsis.[7,8] Mortality by varicella is considered low (6.7/100,000 infected), but the disease may have temporary or permanent sequelae.[9]The varicella vaccine (VV) with live attenuated virus (Oka strain) was developed in Japan in 1974 and its commercialization started in 1987. Varicella is caused by a DNA virus of the Herpesviridae family. It is highly contagious, with an annual incidence of 26---61 cases per 1000 unvaccinated individuals; it usually has a benign course, but can evolve with complications from the virus itself or from secondary bacterial infections in both immunodeficient patients and immunocompetent individuals.1---4. In 1995, the United States (USA) became the first country to include it in the national immunization schedule.[10] The local epidemiological scenario was characterized by an incidence of four million cases, 11,000 hospitalizations, and 100 deaths yearly due to varicella.[5] In 2006, the country introduced the second dose of vaccine for children between 4 and 6 years, in order to reduce community outbreaks. Over the past 20 years, other countries have implemented universal vaccination against this disease in one or two doses, according to the criteria of each country or region, and several studies analyzing the impact of this measure have been published
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