Changes in Patterns of Hospitalized Children With Varicella and of Associated Varicella Genotypes After Introduction of Varicella Vaccine in Australia

Marshall, Helen S. MB BS, MD, MPH*†; McIntyre, Peter MB BS, FRACP, FAFPHM, PhD‡§¶; Richmond, Peter MB BS, MRCP, FRACP; Buttery, Jim P. FRACP, MSc** ††; Royle, Jenny A. MB BS, FRACP, MD**; Gold, Michael S. MD; Wood, Nicholas MB BS, FRACP, PhD‡§¶; Elliott, Elizabeth J. MD‡¶‡‡; Zurynski, Yvonne BAppSc, MAppSc, PhD¶‡‡; Toi, Cheryl S. PhD§§; Dwyer, Dominic E. MD, FRACP, FRCPA¶§§; Booy, Robert MB BS(Hons), MSc, MD, FRACP, FRCPCH‡§¶ ¶¶

Pediatric Infectious Disease Journal: May 2013 - Volume 32 - Issue 5 - p 530–537
doi: 10.1097/INF.0b013e31827e92b7
Vaccine Reports

Background: Varicella in children, although usually mild, can cause hospitalization and rarely death. This study examined patterns of hospitalized children with varicella, and associated varicella genotypes, in 4 tertiary children’s hospitals throughout Australia before and after varicella vaccine was introduced.

Methods: We obtained coded data on discharge diagnoses from each hospital before (1999 to 2001) and after (2007 to 2010) varicella vaccine introduction in 2005, adding active surveillance to capture clinical features, complications and immunization history in the latter period. Varicella vesicles were swabbed, and genotyping of varicella strains was performed by real-time polymerase chain reaction amplification.

Results: Overall, a 68% reduction in coded hospitalizations (varicella, 73.2% [P < 0.001]; zoster, 40% [P = 0.002]) occurred post-vaccine introduction. Of children with detailed clinical data (97 varicella and 18 zoster cases), 46 (40%) were immunocompromised. Only 6 of 32 (19%) age-eligible immunocompetent children were immunized. Complications, most commonly secondary skin infections (n = 25) and neurologic conditions (n = 14), occurred in 44% of children. There were no deaths; but 3 immunocompetent unimmunized children had severe multiple complications requiring intensive care. All strains genotyped were “wild-type” varicella, with Clade 1 (European origin) predominating.

Conclusions: After the introduction of varicella vaccine, coverage of greater than 80% at 2 years of age was achieved, with varicella hospitalizations reduced by almost 70%. Of hospitalized children age-eligible for varicella vaccine, 80% were unimmunized, including all cases requiring intensive care.

From the *The Vaccinology and Immunology Research Trials Unit, Women’s and Children’s Hospital; School of Paediatrics and Reproductive Health, the University of Adelaide, Adelaide; The Children’s Hospital at Westmead; §National Centre for Immunization Research and Surveillance; The University of Sydney, Sydney; Princess Margaret Hospital for Children, Perth; **Department of General Medicine, Royal Children’s Hospital; ††Department of Infectious Diseases, Monash Children’s Hospital, SAEFVIC, Murdoch Children’s Research Institute, Department of Paediatrics, Monash University, Melbourne; ‡‡Australian Paediatric Surveillance Unit; §§Clinical Virology, Centre for Infectious Disease and Microbiology Public Health, ICPMR, Westmead Hospital; and ¶¶Sydney Institute for Emerging Infections and Biosecurity, University of Sydney, Sydney, Australia.

Accepted for publication November 15, 2012.

The Commonwealth Department of Health and Ageing provided funding for the study and the Centre for Infectious Disease and Microbiology Laboratory Services, Westmead for varicella genotyping. H.S.M. is supported by an NHMRC Career Development Fellowship No. 1016272. E.J.E. is supported by the National Health and Medical Research Council of Australia (Practitioner Fellowships 457084 and 1021480). H.S.M. has been a member of vaccine advisory boards for Wyeth (Philadelphia, PA) and GlaxoSmithKline Biologicals (London, UK) and her institution has received funding for investigator led research from Novartis (Washington, DC), GlaxoSmithKline and Sanofi-Pasteur (Swiftwater, PA), and has received travel support from Pfizer, GlaxoSmithKline Biologicals and CSL (King of Prussia, PA) to present scientific data at international meetings. P.C.R. has been a member of vaccineadvisory boards for Wyeth and Baxter (Indianapolis, IN) and has received funding for investigator initiated research from GlaxoSmithKline Biologicals and received travel support from Pfizer and Baxter to present study data at international meetings. R.B. is occasionally funded by organizations such as CSL, Roche (Indianapolis, IN), Sanofi, GSK, Novartis and Pfizer (Wyeth) to attend and present at scientific meetings. Any funding received is directed to a research account at The Children’s Hospital at Westmead and is not personally accepted. J.P.B.’s institution has received compensation for him serving on advisory or data safety monitoring boards for GSK and CSL, and funding for investigator led studies from CSL. D.E.D. has been a member of vaccine advisory boards for GlaxoSmithKline Biologicals. M.S.G., P.M., N.W., E.J.E., Y.Z., C.S.T. and J.A.R. have no conflict of interest to disclose. The authors have no other funding or conflicts of interest to disclose.

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Address for correspondence: Helen S. Marshall, MB BS, MD, MPH, Vaccinology and Immunology Research Trials Unit, Discipline of Paediatrics, Women’s and Children’s Hospital, 2nd floor Clarence-Reiger Building, 72 King William Rd, North Adelaide 5006 South Australia, Australia. E-mail: helen.marshall@adelaide.edu.au.

© 2013 Lippincott Williams & Wilkins, Inc.