CONNAUGHT's HAEMOPHILUS B CONJUGATE VACCINE, PROHIBIT, APPROVED FOR USE IN CHILDREN 18 TO 60 MONTHS; FIRM WILL DISCONTINUE POLYSACCHARIDE HIBVAX
Connaught's Haemophilus b conjugate vaccine, indicated for use in children 18 months to five years of age, will be launched Jan. 11. FDA approved the new vaccine, trademarked ProHIBIT, on Dec. 22, roughly four-and-a-half years after Connaught submitted its product license application. Connaught said it will discontinue distribution of its polysaccharide Haemophilus b vaccine, HibVax, simultaneously with the Jan. 11 introduction of ProHIBIT. ProHIBIT is the first conjugate Haemophilus influenzae b vaccine to be approved by, FDA. In a "Talk Paper" announcing the approval, FDA noted that the conjugate vaccine "appears to more effectively stimulate the body to produce antibodies against the Haemophilus organism than currently available vaccines made from the Haemophilus component alone." The conjugate vaccine is the only Haemophilus b vaccine labeled for general use in children less than 24 months old. Polysaccharide vaccines currently marketed are approved for general use in children 24 to 60 months of age and for children at high risk as early as 18 months. FDA approved labeling for ProHIBIT states that "mean antibody levels induced by ProHIBIT in children 18-20 months of age are 30-fold higher than those induced by polysaccharide vaccines in the same age group." In U.S. immunogenicity studies comparing ProHIBIT to polysaccharide vaccine, 75 of 18 to 21 month olds vaccinated with ProHIBIT had antibody response rates greater than 1.0 mcg/ml, while 24% of 18 to 20 month olds vaccinated with polysaccaride vaccine produced the same response. Connaught said it is pricing ProHIBIT at $13.75 per dose. The company sells its HibVax vaccine for $6.68 per dose. HibVax labeling, however, recommends a booster vaccination, whereas ProHIBIT labeling does not. Based on the 18 to 60 month indication for ProHIBIT, Connaught estimates that "nearly 50% more children at risk for [Haemophilus b diseases] now can be vaccinated than was previously possible." The company explained that 12.5% of the children at risk are in the 18 to 24 month old age group, while 25% are in the 24-month to 60-month age group. The bulk of children at risk of meningitis and other diseases caused by Haemophilus b bacteria are in the age group less than 18 months old. Connaught is also pursuing a ProHIBIT indication for children 2 months to 18 months of age. Two clinical trials, one in Finland and one in Alaska, are currently underway to investigate efficacy of the vaccine in the younger age group. The final date of immunization in both trials is Dec. 31, 1987. The company reported that as of mid-December, ProHIBIT had shown a 91% efficacy rate. The Finnish trial, which began in October 1985, has enrolled 60,000 three month olds and randomized them to receive vaccinations of either ProHIBIT or placebo at three, four, six and 14 months of age. FDA's Vaccines and Related Biological Products Advisory Committee discussed preliminary results from the Finnish study at its Nov. 24 meeting. Some committee members commented that there might be a need for study data from the continental U.S. for approval. Connaught said it has not been asked by FDA to conduct any additional trials for a product license application, and that it believes the Finnish and Alaskan data support efficacy of the vaccine in the two to 18 month olds. Praxis Biologics, the first firm to receive approval for a polysaccharide Haemophilus b vaccine, submitted a PLA for a conjugate vaccine for use in children two months and older in January 1987. Merck is in clinicals with a conjugate Haemophilus b vaccine.
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