LEDERLE ACELLULAR PERTUSSIS VACCINE CLINICALS IN OVER 1,000 CHILDREN SHOW "SIGNIFICANTLY FEWER" REACTIONS V. WHOLE CELL; EQUIVALENT ANTIBODY TITERS
Preliminary results from Lederle's Phase II clinical studies show "significantly fewer" local reactions from Takeda's acellular pertussis vaccine compared with the whole cell vaccine, Lederle Assistant Director for Biologicals Research Cornelia Dekker told a Feb. 8 workshop on acellular pertussis vaccines, held at the National Institutes of Health. Dekker reported results from two U.S., randomized, double-blind studies nearing completion. For the purposes of its preliminary analysis, Dekker said, Lederle looked only at maximum reactions occurring within 72 hours of vaccination. One study was conducted with 4-6 year old children, the other involved 17-24 month old children. The vaccine tested combines Lederle's diphtheria and tetanus components with an acellular pertussis component manufactured by Takeda Chemical Industries of Japan. The Takeda component includes lymphocytosis promoting factor (LPF), filamentous hemagglutinin (FHA) and agglutinogens. Summarizing the results, Dekker told the workshop: "looking at our 4-6 year olds data, you can see that the acellular vaccine is associated with less pain in recipients, less increase in injection-site temperature, fewer local reactions . . . In the 17-24 months old children, administration of the acellular vaccine was once again associated with less pain, less increase in injection [and] fewer local reactions." Systemic reactions to the vaccine, including fever, drowsiness, vomiting, irritability and anorexia, were also monitored. Systemic reactions were similar among 4-6 year olds in both the acellular and whole cell vaccine groups. In the younger children, incidence of fevers was less in the acellular group, but otherwise, systemic reactions were comparable, Dekker said. Immunogenicity data demonstrated that in both age groups, the acellular vaccine produced antibody titers equivalent to or higher than those achieved with the whole cell vaccine, Dekker told the workshop. Antibodies measured included the LPF and FHA. Lederle expects to file for FDA approval of the DTP vaccine in approximately one year. In the meantime, the firm has initiated a comparative study in infants aged 2, 4 and 6 months. The infant study is also a double-blind randomized comparison of the acellular and whole cell vaccines. The Phase I trial of the Takeda vaccine was conducted by Wyeth. Wyeth manufacturers the vaccine for Lederle under contract. In a separate presentation, Connaught's Garry Humphreys described the development of an acellular pertussis vaccine, noting that "further research is in process at Connaught Research Institute on future generation pertussis vaccines with defined, purified components." Presentations were also made by representatives from the National Institute for Child Health and Human Development (NICHD) and Institut Merieux. Charles Lowe, assistant director of the NICHD, described studies on a vaccine composed solely of a "highly purified" pertussis toxin, inactivated by hydrogen peroxide. He reported that the testing showed, "pertussin toxin can be inactivated, and yet retain its immunogenicity after treatment with hydrogen peroxide." Lowe added that "we are in the process of evaluating these vaccines for immunogenicity in clinical studies and are prepared to study this vaccine side by side with a whole cell vaccine." Michel Cadoz, Institut Merieux, said that "our choice for pertussis is definitely a two-component vaccine." He added that the institute is organizing a large multi-center study for further safety and efficacy studies, "knowing that to-date, 2,500 injections have been perfectly safe." Wellcome Research Labs Biological Products Director John Beale expressed concern over abandoning the whole cell vaccine. "Unlike previous presentations," he said, "I want to make some defense for use of the existing whole cell vaccine, because I'm very concerned as a physician that . . . we don't change horses until we're absolutely certain we're changing for the better, as it concerns efficacy and safety.
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