Tripedia has been approved as an injected whooping cough vaccine for children up to three years of age.

Whooping cough, or pertussis, is a highly contagious disease that usually hits children under age three, causing severe coughing and difficulty in breathing. Tripedia is made of just a portion of the killed pertussis bacteria.

This acellular vaccine has also been approved in the United States for booster shots in older children, and it has been used for 15 years in Japan for children of all ages. American infants will be given this acellular vaccine at ages two, four and six months as well as booster shots later.

A large-scale phase III efficacy study was conducted in Germany from 1993 to 1995 and enrolled 16,780 infants between six and 17 weeks of age. Tripedia was administered to 12,517 of the infants. The efficacy of the acellular pertussis vaccine in the German case-control study was 80% for culture-confirmed pertussis cough of 21 days.

In a randomized, double-blind, placebo-controlled efficacy trial of an acellular pertussis vaccine, the pertussis components of Tripedia were shown to be 79% efficacious for culture-confirmed pertussis with cough of over 30 days duration in children. The study included two doses given two months apart, with the first dose given at five to eleven months of age. This study was a large-scale NIH-sponsored study conducted in Sweden from 1986 to 1987 and reported in The Lancet in 1988. The trial studied the efficacy of the two-component acellular vaccine, composed of pertussis toxoid and filamentous hemagglutinin, similar to that contained in the Tripedia vaccine. A three-year unblinded passive follow-up of vaccine and placebo recipients from the Swedish study (reported in Vaccine in 1992) showed a post-trial efficacy of 77% for all culture-proven cases of pertussis and an efficacy of 92% for culture-proven cases with a cough of over 20 days duration.

A safety and immunogenicity study in infants two, four, and six months of age found as much as a six-fold decrease in the rate of tenderness and swelling, as much as an eight-fold decrease in fever greater than 101 degrees fahrenheit, and more than a two-fold decrease in the rate of other systemic reactions (i.e. drowsiness and irritability) reported within 72 hours post-vaccination in those infants who received Tripedia compared with those who received the whole cell DTP vaccine. This randomized, double-blind study was conducted in 672 healthy U.S. infants who received three doses of either whole cell DTP or Tripedia. An Advisory Committee to the FDA concluded that the data provided supported the safety and efficacy of Tripedia for use in infants two, four, and six months of age.

In August 1995, based on the German case-control study, the German government approved the acellular pertussis component in Tripedia for immunization in infants as young as two months of age, using three infant doses followed by a booster in the second year of life.

Tripedia caused fewer of the irritating side effects (fever, irritability, swelling of the injection site) than the pertussis vaccine.

While whooping cough is generally mild, it can cause pneumonia, brain damage, or even death.

Worldwide, whooping cough attacks 50 million children annually, killing about 350,000. In the United States, widespread use of the pertussis vaccine has limited the number of cases to about 4,000 each year, with eight deaths reported in 1994. The government estimates, however, that 10 times as many Americans may actually get sick but go uncounted because of the mildness of the disease.

Today, most states require that infants be immunized against whooping cough with a vaccine made of the entire killed pertussis bacteria.

Very rarely does the vaccine cause brain damage. While the vast majority of the side effects are merely annoying, doctors say they scare some parents enough that they are reluctant to get their children vaccinated.

The FDA panel noted that there is no way to know whether Tripedia causes fewer of the rare brain-damage cases associated with the current shots. That side effect is so rare that it takes tens of thousands of injections to detect. The panel called for continued study of the vaccine once it is sold to try to catch those rare problems.

Pertussis is the "P" in the "DPT" combination of vaccines routinely given to infants in the United States. The other vaccines are for diptheria and tetanus. DPT shots are recommended at two, four, and six months, with booster doses at 12 to 18 months and between four and six years.