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Administration of two doses of hepatitis A (HA) vaccine to childrenor = 2 years of age has been shown to be protective. The present study assessed whether HA vaccine can be administered as early as 6 months of age and whether it can be administered concomitantly with a hexavalent (HV) vaccine at this age.In an open label, randomized, parallel group study, the liquid HV vaccine (HEXAVAC) (diphtheria, tetanus, 2-component acellular pertussis, inactivated poliomyelitis vaccine, Haemophilus influenzae type b conjugated to tetanus protein and hepatitis B) was administered at 2, 4, 6, and 12 months of age to all children. HA vaccine (VAQTA) was given at 7 and 13 months in the separate administration group (Group 1) and at 6 and 12 months in the concomitant administration group (Group 2). Serum samples were obtained at 2, 7, 12, and 14 months in Group 1 and at 2, 7, 12, and 13 months in Group 2. The primary immunogenicity outcomes were the seroconversion rates for HA 1 month after the second dose of HA vaccine in initially seronegative subjects, and the seroconversion rates for each HV antigen 1 month after the third dose of the HV vaccine (both at 7 months of age).HA seropositivity rates 1 month after the second dose were 100% in both groups, regardless of initial serostatus. The responses to each HV antigen 1 month after the third dose were similar in both groups. The vaccines were generally well tolerated in both groups regardless of vaccine(s) administered.A schedule of two doses of HA vaccine, 6 months apart beginning at 6 months of age is highly immunogenic and well tolerated when administered alone or concomitantly with HV vaccine at 6 and 12 months of age.

A multicenter clinical trial was conducted among 757 healthy adolescents and adults, 13-54 years, to compare two regimens of Oka/Merck varicella vaccine with respect to safety, tolerability, and immunogenicity. Participants were randomized to receive two injections of vaccine either four or eight weeks apart and were followed for clinical reactions and serologic response. The two vaccine regimens were equally well tolerated. The seroconversion rates (gpELISA) four weeks after injection 1 and 2 were 72 and 99%, respectively, for those who received vaccine four weeks apart and 78 and 99%, respectively, for those who received vaccine eight weeks apart. The differences in seroconversion rates were not statistically significant. However, delaying the second dose to eight weeks resulted in a higher antibody titer one month after the second injection. Administration of a two-dose regimen of varicella vaccine to susceptible adolescents and adults is well tolerated and highly immunogenic.

Oka strain varicella vaccine generally has been well tolerated by children with acute lymphocytic leukaemia (ALL) in remission and has induced protection against disease caused by wild-type varicella virus. At the end of 1985, four extensive vaccine-associated rashes were reported among children on maintenance chemotherapy. Steroid therapy in the week before vaccination or in the week following vaccination was significantly associated with rash in a retrospective analysis (odds ratio = 3.84, p = 0.0006). These findings were confirmed prospectively (OR = 2.38, p less than 0.05, one-sided) in a second smaller group of children with ALL on maintenance therapy who received varicella vaccination after the end of the data collection for the initial study but before the relationship between rash and steroids was discovered. As a result of these studies, investigators have been asked to withhold steroids for 1 week before vaccination and to delay resumption of steroid therapy for at least 2 weeks after vaccination. These results should serve as a caution that vaccination of these children should be undertaken only with full knowledge of their therapeutic regimen and a thorough clinical understanding of the competing risks of varicella, vaccination and modification of the child's chemotherapy.