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Canadian Journal of Infectious Diseases
Volume 13, Issue 6, Pages 382-286
http://dx.doi.org/10.1155/2002/907087
Original Article

Three-Year Follow-Up of protection Rates in Children Given Varicella Vaccine

David W Scheifele,1 Scott A Halperin,2 and Francisco Diaz-Mitoma3

1British Columbia’s Children’s Hospital, Vancouver, British Columbia, Canada
2IWK Health Centre, Halifax, Nova Scotia, Canada
3Children’s Hospital of Eastern Ontario, Ottawa, Ontario, Canada

Received 3 August 2001; Revised 23 January 2002

Copyright © 2002 Hindawi publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

OBJECTIVE: To determine the rate and severity of subsequent varicella and zoster among children given a varicella vaccine.

DESIGN: Retrospective survey conducted three years after vaccination, using standardized telephone interviews.

SETTING: Three urban Canadian centres (Halifax, Ottawa and Vancouver).

pARTICIpANTS: Of 475 eligible children, 431 aged three to 15 years participated.

INTERVENTION: participants had received one dose of a live, attenuated varicella vaccine (Oka/GSK) an average of 36 months earlier.

MAIN OUTCOME MEASURES: Interviewers asked about known varicella exposures and obtained descriptions of any illnesses reported as varicella or zoster. Reported varicella was classified as definite (vesicles present, physician confirmation), probable (vesicles reported), suspected (nonvesicular rash, recent contact with varicella) or unlikely (nonvesicular rash, no known contact).

RESULTS: parents reported 257 within-home exposures to varicella and alleged that 80 subjects had had varicella rash after exposure. Of these, 40 cases were classified as definite or probable (vesicles present; rate 9.3% or 3.1% per year on average), 31 as suspected (no vesicles; rate 2.4% per year) and nine as unlikely. All rash illnesses were mild: among children with vesicles, 75% were said to have up to 10 and none had more than 100. The outcome of 76 exposures to household members with varicella was evaluable: 25 (32.9%) resulted in a rash, and 13 (17.1%) of those involved vesicles (maximum 40 lesions). parents alleged that three subjects had zoster, but only one illness was definite (six vesicles, physician confirmed).

CONCLUSIONS: Varicella vaccination completely prevented the development of typical chickenpox during the three years of observation. Breakthrough infections were infrequent (about 5% per year) and mild. Zoster was rare.