NICHD ANNOUNCES RESULTS FROM PHASE III CLINICAL TRIAL FOR NORTH AMERICAN VACCINE'S DTaP VACCINE.

BELTSVILLE, Md.--(BUSINESS WIRE)--Nov. 22, 1994--North American Vaccine (AMEX:NVX) announced today that the National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health today released "promising results" from the recently completed Phase III clinical trial of the Company's combined diphtheria, tetanus, and acellular pertussis (DTaP) vaccine. The DTaP vaccine was developed by the Company in collaboration with the Danish government enterprise Statens Seruminstitut (SSI). In its press release, the NICHD stated that the results of the Phase III trial indicate that the Company's DTaP vaccine is estimated to have been 71 percent effective under epidemic conditions in preventing pertussis (whooping cough) as defined by the World Health Organization (WHO). The NICHD concluded its press release by stating, "The very encouraging results of this vaccine trial justify the expectation that in the near future, infants will have an acellular pertussis vaccine which is not only effective but remarkably safe."

"Even more noteworthy was the absence of (significant) adverse side effects," said the NICHD. "In this study, no children in either group had severe adverse reactions attributed to vaccination. In fact, the vaccine proved to be remarkably safe. The incidence of all side effects, local and systemic, was far below that reported when infants receive the currently used whole-cell vaccine. In the United States, the frequency of significant adverse side effects, local and systemic, with the currently used whole-cell vaccines has caused concern and prompted the search for a safer vaccine."

NICHD Associate Director Dr. Charles Lowe, who was project officer and associate investigator for the study, called the trial results "significant," adding: "The study is important in demonstrating that a vaccine with a single component, a detoxified pertussis toxin, is capable of preventing disease in a substantial portion of infants receiving the vaccine, even under demanding epidemic conditions. The vaccine appeared to perform well in both efficacy and safety. The safety results are particularly gratifying because of the remarkable absence of significant adverse events. We are now performing an analysis of a household contact study and assessing the efficacy of the vaccine under non-epidemic conditions. These results will be reported shortly."

The trial's two principal investigators, Swedish pediatricians Drs. John Taranger and Birger Trollfors, concurred with Dr. Lowe's assessment, explaining that, "the vaccine was tested under stringent conditions during an epidemic of pertussis in Goteborg, Sweden. These results are quite promising, and we would expect that under non-epidemic conditions the calculated efficacy of the vaccine would be even higher." Drs. Taranger and Trollfors said that they now plan to go ahead with a clinical trial, already approved by the appropriate authorities, in which they will give the Company's acellular pertussis vaccine to the children who were in the trial's control group and only got vaccinated against diphtheria and tetanus.

"The Company is pleased to report these promising results from the Phase III clinical trial," Dr. Sharon Mates, President of North American Vaccine stated. "This marks the culmination of years of research, development, scale-up and production efforts to produce a safe and effective acellular pertussis vaccine for the prevention of whooping cough in infants and children."

The safety and efficacy data from the Phase III clinical trial will be incorporated into a product license application (PLA) to be filed with the U.S. Food and Drug Administration (FDA), Dr. Mates said. The Company anticipates that the PLA will be submitted to the FDA during the first quarter of 1995 and will seek approval to market the DTaP vaccine for all five doses required for pediatric immunization. In the U.S., primary immunization against diphtheria, tetanus and pertussis is required at 2, 4, and 6 months of age with booster doses required at 15-18 months of age and just prior to grade school entry. Currently, there is no DTaP vaccine licensed by the FDA for the three primary doses administered to infants during the first year of life.

"The Company looks forward to working with the FDA to obtain licensure for this vaccine for all five (primary and booster) doses," said Dr. Mates. "The Company will also be filing for regulatory approval to market the DTaP vaccine in selected European countries. The Company is presently expanding its production facility, which is scheduled to be completed in early 1995, and intends to introduce the DTaP vaccine after receiving the appropriate regulatory approvals."

The clinical trial, which was conducted under NICHD sponsorship in Goteborg, Sweden beginning in 1991, involved a total of 3,335 infants at completion, of which approximately one-half received the Company's DTaP vaccine and one-half received a combined diphtheria and tetanus (DT) vaccine as a control. The purpose of this randomized, double-blind, placebo-controlled clinical trial was to establish the safety and efficacy of the Company's DTaP vaccine for the prevention of pertussis (whooping cough) in infants.

The NICHD reported that on average the children were followed for about 20 months after their third vaccination by a team of nurses trained in field work who kept the infants and their households under close surveillance. All coughing episodes lasting seven days or more were evaluated for possible pertussis infection. During the study, 312 children developed pertussis (whooping cough) meeting the WHO definition. The NICHD reported that 240 children who received the DT vaccine as a control contracted pertussis (whooping cough), as compared to 72 children who received the Company's DTaP vaccine.

North American Vaccine, Inc. is engaged in the research, development and production of vaccines for the prevention of human infectious disease.

CONTACT: North American Vaccine, Beltsville

Kelley Jenkins, 202/625-6930