An FDA advisory committee agreed North American Vaccine'scombined diphtheria, tetanus and acellular pertussis (DTaP) vaccine,called Certiva, was safe and effective for infants and children, butdiscussion of some data apparently worried investors, causing thestock to drop 13 percent Wednesday.

The genetically engineered acellular pertussis component of thechildhood vaccine was developed as a safer substitute for the whole-cell version, which can produce side effects. The DTaP vaccines areexpected to replace the traditional DTP shots given to youngsters infive doses, one at two months, four months, six months, 15-18months and four to six years.

North American Vaccine, of Beltsville, Md., is one of fourcompanies making a DTaP vaccine. Connaught Laboratories Inc., ofSwiftwater, Pa., a subsidiary of Rhone-Poulenc Group in Paris, hasthe only FDA-approved DTaP vaccine, called Tripedia, on the

In addition to North American, other companies with DTaP vaccinesunder review by the FDA are SmithKline Beecham plc, of London,Chiron Corp., of Emeryville, Calif., and Wyeth-Lederle Vaccines andProducts, of Radnor, Pa., a division of American Home ProductsCorp., of Madison, N.J.

The FDA's Vaccines and Related Biological Products AdvisoryCommittee Tuesday recommended North American's Certiva for usein children at two months, four months, six months and 15-18months.

Data on use of a consecutive fifth dose of Certiva was not availablebecause North American began its studies in 1991 and the firstchildren enrolled had not reached the appropriate age prior to filingfor FDA review.

However, the FDA advisory panel said Certiva was safe and effectiveas a fifth dose for children who received four previous DTPvaccinations with whole-cell pertussis components based on datafrom more than 200 youngsters.

The confusion, said North American President Sharon Mates, arosein discussion of the effectiveness of a fourth Certiva administrationfollowing inoculation with three whole-cell pertussis vaccinations.

The company submitted data from 42 patients demonstrating Certiva,following three traditional DTP administrations, was safe andeffective. But some panel members questioned whether enoughsubjects had been evaluated to draw broad conclusions oneffectiveness of Certiva as a fourth dose.

Mates said North American will continue to supply results fromongoing trials of Certiva, but she added the FDA advisory group didnot say the company was required to file more data to achieveapproval of Certiva.

Concern over the possibility of a delay in clearance of the vaccine,which would be North American's first product on the U.S. market,apparently contributed to the stock's decline Wednesday, the dayafter the advisory panel review.

North American ended the day at $21.125, off $3.125.

Some analysts, however, said they expect FDA approval of Certiva inthe next three months. North American's marketing partner forCertiva is Abbott Laboratories, of Abbott Park, Ill.

The FDA advisory panel also recommended Certiva for use withpolio, Haemophilus influenza type b, hepatitis B and measles-mumps-rubella vaccines.

Certiva has been approved in Sweden and Denmark. n

-- Charles Craig

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