title: Safety and immunogenicity of one vs. two injections of Oka/Merck varicella vaccine in healthy children.
abstract: OBJECTIVE
  To compare the safety and immunogenicity of a one- vs. two-dose regimen of Oka/Merck varicella vaccine in approximately 2000 healthy children 12 months to 12 years of age.
  
  
  METHODS
  Subjects with a negative history of varicella were randomized to receive either one or two injections of the vaccine given 3 months apart and were followed for clinical reactions and serologic response (glycoprotein-based enzyme-linked immunosorbent assay).
  
  
  RESULTS
  Both one- and two-dose vaccine regimens were generally well-tolerated. The incidences of varicelliform rash and fever were less frequent after the second injection. However, a slight increase in the incidence of injection site reactions was noted after the second injection; these were generally mild. Seroconversion rates by glycoprotein-based enzyme-linked immunosorbent assay were 98.2% (1700 of 1731) after one injection and 99.9% (717 of 718) after two injections. A significant (P < 0.001) boost in geometric mean titers was observed in children who received a second injection of vaccine 3 months after the first injection. Of the children who seroconverted at 6 weeks postregimen (one or two doses as assigned), 99.8% (528 of 529) of the one-dose group and 99.8% (473 of 474) of the two-dose group maintained antibody to varicella at 1 year with geometric mean titers of 19.5 and 31.2, respectively.
  
  
  CONCLUSIONS
  Administration of a one- or two-dose regimen of the live Oka/Merck varicella vaccine (VARIVAX) is immunogenic and is generally well-tolerated in healthy children 1 to 12 years old. Antibody to varicella persists in > 99% of vaccinees 1 year after vaccination regardless of a one- or two-dose regimen. Long-term follow-up studies of this cohort of children may determine whether a two-dose regimen offers superior protection against chickenpox.
authors.affiliation: Merck Research Laboratories, West Point, PA, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Ngai
authors.forename: B O
authors.initials: BO
authors.lastname: Staehle
authors.forename: B J
authors.initials: BJ
authors.lastname: Kuter
authors.forename: N M
authors.initials: NM
authors.lastname: Cyanovich
authors.forename: I
authors.initials: I
authors.lastname: Cho
authors.forename: H
authors.initials: H
authors.lastname: Matthews
authors.forename: P
authors.initials: P
authors.lastname: Keller
authors.forename: A M
authors.initials: AM
authors.lastname: Arvin
authors.forename: B
authors.initials: B
authors.lastname: Watson
authors.forename: C J
authors.initials: CJ
authors.lastname: White
mesh_terms: D000914:Antibodies, Viral / Q000096:biosynthesis; D019433:Chickenpox Vaccine; D002648:Child; D002675:Child, Preschool; D004306:Dose-Response Relationship, Immunologic; D003875:Drug Eruptions / Q000276:immunology; D005334:Fever / Q000276:immunology; D014645:Herpesvirus 3, Human / Q000276:immunology*; D006801:Humans; D007223:Infant; D015337:Multicenter Studies as Topic; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology / Q000494:pharmacology; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D019433:Chickenpox Vaccine; D014613:Vaccines, Attenuated; D014765:Viral Vaccines