A Study for the Necessity of Virus Titer of Varicella Vaccine Presently Used

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  • 現在使用されている水痘ワクチンの力価の必要性
  • ゲンザイ シヨウ サレテ イル スイトウ ワクチン ノ リキカ ノ ヒツヨウセイ

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Abstract

Recently available varicella vaccine titers are several dozen times higher than the formulation standard in accompanying information, i.e., ≧1,000PFU/dose. We investigated changes in immunogenicity associated with vaccination using a reduced dose whose virus titer was close to that used when the vaccine was developed, and examined the need for the virus titer presently used. <BR>In a non blinded study of 43 children with no history of varicella infection, we administered 0.1mL of varicella vaccine （1/5 of the normal dose） to 20 children 1 year 0 month to 4 years 5 months old （median : 1 year 5 months） and the standard 0.5mL dose to 23 children 1 year 2 months to 3 years 7 months old （median : 1 year 9 months）. We measured IAHA and gpELISA antibody titer before vaccination and 4 to 6 weeks after vaccination. We defined “positive” as ≧2 fold of IAHA titer and ≧50U of gpELISA antibody titer. We administered an additional 0.5mL of varicella vaccine to children whose IAHA titer failed to show seroconversion and remeasured antibody titer 4 to 6 weeks after revaccination. <BR>IAHA seroconversion was 25.0％ （5/20） and gpELISA seroconversion 55.0％ （11/20） in the 0.1mL vaccination group, which was lower than that of 76.2％ （16/21） and 87.0％ （20/23）, IAHA p＜0.01, gpELISA p＜0.05, in the 0.5mL vaccination group. We administered an additional vaccination to 19 children―15 in the 0.1mL vaccination group and 4 in the 0.5mL vaccination group―with 100％ seroconversion for both methods. Mean antibody titer after revaccination in the 0.1mL vaccination group （IAHA 26.0, gpELISA 103.7） was higher than those in the 0.5mL vaccination group who seroconverted following initial vaccination （IAHA 24.5,gpELISA 102.6） （p＜0.01）. We also measured virus titer in the remaining vaccine following vaccination of 0.1 mL（n＝20）, and estimated virus titer administered to the 0.1mL vaccination group to be 2,600 - 6,400PFU/dose. <BR>Varicella vaccine immunogenicity decreased if dosage was reduced to 1/5 of the standard dose, indicating that the present virus titer is necessary to maintain adequate immunogenicity. An additional administration of the standard dose to children who failed to seroconvert after initial 0.1mL administration produced high antibody titers thought to constitute a booster effect.

Journal

  • Kansenshogaku Zasshi

    Kansenshogaku Zasshi 86 (6), 749-754, 2012

    The Japanese Association for Infectious Diseases

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