When this trial was initiated, the combined measles, mumps and rubella (MMR) vaccine was licensed for subcutaneous administration in all European countries and for intramuscular administration in some countries, whereas varicella vaccine was licensed only for subcutaneous administration. This study evaluated the intramuscular administration of an MMR vaccine (M-M-RvaxPro^®) and a varicella vaccine (VARIVAX^®) compared with the subcutaneous route.

An open-label randomised trial was performed in France and Germany. Healthy children, aged 12 to18 months, received single injections of M-M-RvaxPro and VARIVAX concomitantly at separate injection sites. Both vaccines were administered either intramuscularly (IM group, n = 374) or subcutaneously (SC group, n = 378). Immunogenicity was assessed before vaccination and 42 days after vaccination. Injection-site erythema, swelling and pain were recorded from days 0 to 4 after vaccination. Body temperature was monitored daily between 0 and 42 days after vaccination. Other adverse events were recorded up to 42 days after vaccination and serious adverse events until the second study visit.

Antibody response rates at day 42 in the per-protocol set of children initially seronegative to measles, mumps, rubella or varicella were similar between the IM and SC groups for all four antigens. Response rates were 94 to 96% for measles, 98% for both mumps and rubella and 86 to 88% for varicella. For children initially seronegative to varicella, 99% achieved the seroconversion threshold (antibody concentrations of ≥ 1.25 gpELISA units/ml). Erythema and swelling were the most frequently reported injection-site reactions for both vaccines. Most injection-site reactions were of mild intensity or small size (≤ 2.5 cm). There was a trend for lower rates of injection-site erythema and swelling in the IM group. The incidence and nature of systemic adverse events were comparable for the two routes of administration, except varicella-like rashes, which were less frequent in the IM group.

The immunogenicities of M-M-RvaxPro and VARIVAX administered by the intramuscular route were comparable with those following subcutaneous administration, and the tolerability of the two vaccines was comparable regardless of administration route. Integration of both administration routes in the current European indications for the two vaccines will now allow physicians in Europe to choose their preferred administration route in routine clinical practice.

ClinicalTrials.gov NCT00432523