Responses to human diploid cell rabies vaccine: neutralizing antibody responses of vaccinees receiving booster doses of human diploid cell rabies vaccine.

Rabies neutralizing antibody levels were determined before and after administration of a booster-dose of Wyeth rabies vaccine (WRV) in persons immunized earlier with either duck embryo vaccine (DEV) or with WRV. Virtually all those receiving an initial 3-dose regimen of WRV (0, 7 and 21--28 days) still had neutralizing antibody one year later, but there was a decline in titer from 10--50 IU per ml at 35 days to about 1--3 IU. Only one-half of those receiving DEV as the primary vaccine had even detectable antibody one year later. All volunteers responded anamnestically to a single WRV booster given 8--12 months after either primary vaccine. Those given WRV initially had much higher antibody levels than those given DEV, but after the WRV booster antibody levels in all vaccinees remained high, even one year later.