BACKGROUND: At present, in the event of re-exposure to rabies, 2 booster doses are recommended for people who have been previously vaccinated with cell culture rabies vaccines by the conventional intramuscular route. As the intradermal route of vaccination is likely to be introduced in the future, we investigated the immune response to a cell culture rabies vaccine after crossing over from the intramuscular to the intradermal route and vice versa. METHODS: Twenty healthy adult volunteers who had received a primary course of rabies vaccination with purified chick embryo cell rabies vaccine by either the intramuscular (n = 10) or intradermal (n = 10) route received booster vaccination with the same vaccine by the alternative route. The regimen used was 0.1 ml of vaccine by the intradermal route at two sites (deltoid area) for the intramuscular group, or 1 ml of vaccine by the intramuscular route (deltoid muscle) to the intradermal group on days 0 and 3. RESULTS: There was a 15-fold rise in the rabies virus neutralizing antibody response both by the intradermal and intramuscular routes of booster vaccination (p < 0.0001). Thus, the change of route of purified chick embryo cell booster vaccination did not alter the anamnestic immune response to the vaccine. No side-effects were observed after vaccination with either of the routes. CONCLUSION: Purified chick embryo cell vaccine was found to be safe and immunologically efficacious following booster vaccination after cross-over from the intradermal to the intramuscular route and vice versa.
BACKGROUND: At present, in the event of re-exposure to rabies, 2 booster doses are recommended for people who have been previously vaccinated with cell culture rabies vaccines by the conventional intramuscular route. As the intradermal route of vaccination is likely to be introduced in the future, we investigated the immune response to a cell culture rabies vaccine after crossing over from the intramuscular to the intradermal route and vice versa. METHODS: Twenty healthy adult volunteers who had received a primary course of rabies vaccination with purified chick embryo cell rabies vaccine by either the intramuscular (n = 10) or intradermal (n = 10) route received booster vaccination with the same vaccine by the alternative route. The regimen used was 0.1 ml of vaccine by the intradermal route at two sites (deltoid area) for the intramuscular group, or 1 ml of vaccine by the intramuscular route (deltoid muscle) to the intradermal group on days 0 and 3. RESULTS: There was a 15-fold rise in the rabies virus neutralizing antibody response both by the intradermal and intramuscular routes of booster vaccination (p < 0.0001). Thus, the change of route of purified chick embryo cell booster vaccination did not alter the anamnestic immune response to the vaccine. No side-effects were observed after vaccination with either of the routes. CONCLUSION: Purified chick embryo cell vaccine was found to be safe and immunologically efficacious following booster vaccination after cross-over from the intradermal to the intramuscular route and vice versa.