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Published on: July 9, 2014
The effect of funded varicella immunization programs on varicella-related hospitalizations in IMPACT centers, Canada,
Ben Tan1, Julie Bettinger, Athena McConnell
1Department of Pediatrics, Royal University Hospital, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. ben.tan@usask.ca
Insights
Publicly funded varicella vaccination programs significantly reduced hospitalizations in Canadian children. The varicella vaccine led to an 88% decline in earlier program centers and an 81% decline in later program centers by 2008.
Area of Science:
- Pediatric infectious disease surveillance
- Vaccine-preventable disease epidemiology
- Public health program evaluation
Background:
- The Immunization Monitoring Program, Active (IMPACT) centers in Canada initiated active surveillance for varicella (chickenpox) hospitalizations post-vaccine authorization.
- Publicly funded routine varicella immunization programs were implemented sequentially across Canadian provinces and territories starting between 2000-2002 (earlier programs) and 2004-2007 (later programs).
Purpose of the Study:
- To assess the impact of sequential, publicly funded varicella immunization programs on varicella-related hospitalizations in Canadian children.
- To determine if a decline in varicella hospitalizations was evident by 2008 across 12 IMPACT centers following vaccine program implementation.
Main Methods:
- Active surveillance data from 12 IMPACT centers (2000-2008) were analyzed, differentiating between provinces with earlier and later immunization program introductions.
- Clinical characteristics, including age, gender, underlying health status, complications, and length of stay, were documented for hospitalized varicella cases.
- Breakthrough varicella cases (occurring despite vaccination) were identified and their clinical features described.
Main Results:
- Varicella-related hospitalizations declined sooner in areas with earlier immunization programs (by 2002-2003) compared to later programs (by 2007-2008).
- By 2008, varicella hospitalizations decreased by 88% in earlier program centers and 81% in later program centers, with the largest decline observed in the 1-4 year age group.
- Breakthrough varicella cases represented 2% of all hospitalizations, increasing over time, with a majority occurring in immunocompromised children.
Conclusions:
- Publicly funded varicella vaccination programs have demonstrably reduced varicella-related hospitalizations in Canadian children.
- The observed decline suggests both direct vaccine effectiveness and indirect protection (herd immunity) contributing to reduced disease burden.
- The findings support the long-term public health benefits of widespread varicella immunization programs.
Background:
The 12 Immunization Monitoring Program, Active (IMPACT) centers that represent 90% of pediatric tertiary care beds in Canada conducted active surveillance for varicella-related hospitalizations and complications from 1999 onward, after varicella vaccine was authorized. Publicly funded routine immunization programs at 12 or 15 months of age were introduced by 5 provinces and territories (prov/terr) in 2000 to 2002 (earlier programs, EP) and by 8 prov/terr in 2004 to 2007 (later programs, LP).
Objective:
To determine whether the number of varicella-related hospitalized cases had declined by 2008 at 12 IMPACT centers after the sequential introduction of publicly funded varicella immunization programs in Canada.
Methods:
Varicella-related hospitalizations from 2000 to 2008 in the prov/terr with EP were under surveillance by 3 IMPACT centers (Halifax, Edmonton, Calgary), whereas the prov/terr with LP were under surveillance by the remaining 9 centers. The age, gender, underlying health status, varicella complications, and length of stay in hospital and the pediatric intensive care unit were documented. Breakthrough cases were identified and their clinical characteristics described.
Results:
Between 2000 and 2008, the number of varicella-related hospitalized cases in IMPACT centers declined relatively sooner in prov/terr with EP (by 2002 to 2003), as compared to those with LP (only by 2007 to 2008). In 2008, varicella-related hospitalized cases declined by 88% in the EP centers, and by 81% in the LP centers. In all IMPACT centers, the greatest decline occurred in the 1-4 years age group (90% decline), with smaller declines in both <1 year and 5-9 years age groups (78% and 76% decline, respectively). Breakthrough disease accounted for 39 (2%) cases, with the proportion due to breakthrough increasing from 0.9% in 2000 to 2001, to 2% in 2003 to 2004 and 9.5% in 2007 to 2008. The majority (72%) of breakthrough cases were in immunocompromised children.
Conclusions:
Publicly funded varicella vaccination programs have led to a significant decline in varicella-related hospitalizations in Canadian children, as a result of direct effects of the program beginning within 1 to 2 years after the start, as well as probable indirect protection of children outside the vaccinated cohort.
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