Antibody response of patients after postexposure rabies vaccination with small intradermal doses of purified chick embryo cell vaccine or purified Vero cell rabies vaccine

Although the introduction of tissue culture vaccines for rabies has dramati cally improved the immunogenicity and safety of rabies vaccines, they are o ften prohibitively expensive for developing countries. To examine whether s maller doses of these vaccines could be used, we tested the safety and immu nogenicity of purified chick embryo cell vaccine (PCECV) on 211 patients in Thailand with World Health Organization (WHO) category II and III exposure s to rabies. The patients presented at two Thai hospitals and were randomiz ed into three groups. Patients in Group 1 received 0.1 ml PCECV intradermal ly at two sites on days 0, 3, 7, and at one site on days 30 and 90. Group 2 was treated similarly, except that purified Vero cell rabies vaccine (PVRV ) was used instead of PCECV. Group 3 received 1.0 ml PCECV intramuscularly on days 0, 3, 7, 14, 30 and 90. After 0, 3, 7, 14 30 and 90 days serum was collected from the subjects and the geometric mean titres (GMTs) of rabies virus neutralizing antibody determined. After 14 days the GMT of 59 patient s vaccinated intradermally with PCECV was equivalent to that of patients wh o received PVRV. Adverse reactions were more frequent in patients who recei ved vaccines intradermally, indicating the reactions were associated with t he route of injection, rather than the vaccine per se. We conclude that PCE CV is a safe and highly immunogenic vaccine for postexposure rabies vaccina tion when administered intradermally in 0.1 ml doses using the two-site met hod ("2,2,2,0,1,1") recommended by WHO.