CLINICAL DATA ON INVESTIGATIONAL VACCINES PRESENTED AT 95TH GENERAL MEETING OF THE ASM IN WASHINGTON, DC.

BELTSVILLE, Md.--(HealthWire)--May 24, 1995--North American Vaccine (AMEX:NVX) announced today that the investigators for the clinical trials of the Company's DTaP-IPV and DTaP vaccines presented data at the American Society of Microbiology (ASM) meeting in Washington, DC.

At ASM, Dr. Iver Heron, from Statens Seruminstitut, reported on the results from the clinical study conducted in Denmark on the Company's combined DTaP-IPV vaccine for the prevention of diphtheria, tetanus, pertussis (whooping-cough) and polio. The trial compared the combined DTaP-IPV vaccine to the standard Danish protocol of giving a DT-IPV vaccine and a whole-cell pertussis vaccine separately to Danish infants. The data revealed that there were no significant adverse reactions attributable to the combined DTaP-IPV vaccine and that there has been no clinically relevant interference among the six different components of the vaccine in eliciting specific immune responses. The study further demonstrated that the combined DTaP-IPV vaccine induced vigorous T-cell stimulation and that cytokine release was specifically induced. T-cell and cytokine stimulation are important because they assist the body in defending against infection and disease. Dr. Heron concluded that the Company's patented acellular pertussis vaccine induced a vigorous T-cell response after the second and third injections and that high levels of immunity against all components were achieved with no indication of serious immunological interactions.

In his presentation at ASM, Dr. John Taranger, the Swedish co-principal investigator, reported on the results from the Phase III clinical study of the Company's DTaP vaccine for the prevention of diphtheria, tetanus and pertussis. In addition to the efficacy figures previously reported by the National Institutes of Health, Dr. Taranger revealed that the Company's DTaP vaccine successfully ameliorated disease in children who contracted pertussis infection. The data from the clinical trial indicates that of the children who contracted pertussis, those who received the Company's DTaP vaccine had milder, less severe cases of disease and for a shorter period of time. Specifically the data revealed that more than a majority of the children who received the DTaP vaccine had no whooping attacks or cough with vomiting. Additionally, the median duration in days of whooping and vomiting was zero in the DTaP vaccinated group as compared to greater than or equal to 20 days in the control group that received a combined diphtheria-tetanus (DT) vaccine.

The results of the Phase III clinical study also revealed that the Company's DTaP vaccine had no significant adverse reactions and that the incidence of less severe, local reactions was similar between the DTaP vaccinated group and the DT control group. The presentation revealed that during the course of three injections of the DTaP vaccine, the incidence of redness and swelling greater than or equal to four centimeters was one-tenth of one percent after the first injection, two percent after the second injection, and ten percent or less after the third injection. Rates of fever were nearly identical in the DTaP and DT vaccinated groups both during the first 48 hours and during the week following vaccination.

Dr. Taranger concluded that the Company's DTaP vaccine is safe with no serious vaccine related side-reactions and no child was withdrawn from the study due to vaccine associated safety concerns. Dr. Taranger further concluded that the vaccine is efficacious in that the disease incidence was reduced by 71% in an area with epidemic outbreak of pertussis. The attack rate of disease was 14.4 percent in the control group versus four percent in the DTaP vaccinated group. Moreover, the vaccine significantly attenuated the clinical course of disease in those 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 diseases.

For further information contact: Sharon Mates, Ph.D., President, North American Vaccine, Inc., 12103 Indian Creek Court, Beltsville, Maryland 20705 [phone].

CONTACT: North American Vaccine, Beltsville

Sharon Mates, Ph.D., 301/470-6100