Safety and immunogenicity of new cell-cultured smallpox vaccine compared with calf-lymph derived vaccine: a blind, single-centre, randomised controlled trial.

BACKGROUND: US government organisations have identified the need for a new smallpox vaccine to replenish limited stocks of the approved, calf-lymph derived vaccine, the manufacture of which is no longer acceptable. We aimed to compare the safety and immunogenicity of the new cell-cultured smallpox vaccine (CCSV) to that of the calf-lymph derived vaccine (as a positive control) in 350 healthy, adult volunteers. METHODS: We did a randomised controlled study at the University of Kentucky Medical Center. We randomised 150 vaccinia-naive volunteers, aged 18-30 years, and 100 vaccinia-non-naive people, aged 32-65 years, to equivalent doses of either CCSV or test vaccine (2.5x10(5) plaque-forming units) by 15 puncture scarification in double-blind fashion. Immunogenicity was assessed by pock formation (take rate), humoral immune response by plaque-reduction neutralisation titres, and cellular immune response by vaccinia-specific, interferon-gamma T-cell quantification, cytotoxicity, and T-cell proliferation response. A further 100 vaccine-naive individuals, aged 18-30 years, received one of five doses of CCSV (undiluted, diluted 1 in 5, 1 in 10, 1 in 25, and 1 in 50) in single-blind fashion. Routine laboratory assessments, physical examinations, and recording of adverse events were done to assess vaccine safety. The primary endpoints were safety and reactogenicity (take rate) of CCSV. FINDINGS: 349 (99.7%) of 350 volunteers developed pock lesions; one vaccinia-naive individual who received a 1 in 25 dilution of CCSV did not. The rate of adverse events related to vaccine and the extent of humoral and cellular immune responses did not differ between the vaccine groups in vaccinia-naive or non-naive people. CCSV was immunogenic in vaccine-naive volunteers at a dose 50 times lower than that approved for Dryvax. INTERPRETATION: CCSV seems to be a safe and immunogenic alternative to calf-lymph derived vaccine for both vaccinia-naive and non-naive people.

Urticaria, exanthems, and other benign dermatologic reactions to smallpox vaccination in adults.

A phase 1 smallpox vaccine trial involving 350 adult volunteers was conducted. Of these subjects, 250 were naive to vaccinia virus vaccine (i.e., "vaccinia naive"). Volunteers received a new cell-cultured smallpox vaccine or a live vaccinia virus vaccine. Nine self-limiting rashes (3.6%) were observed in the vaccinia-naive group. None of the vaccinia-experienced patients had a rash. Rashes appeared 6-19 days after vaccination and had 5 different clinical presentations. Five volunteers had urticarial rashes that resolved within 4-15 days, 1 had an exanthem that lasted 20 days, and 1 each presented with folliculitis, contact dermatitis, and erythematous papules found only on the hands and fingers. Volunteers reported pruritus, tingling, and occasional headaches. Relief was obtained with antihistamine and acetaminophen therapy. No volunteer experienced fever or significant discomfort.