Preventing pertussis in adolescents and adults could provide another means of preventing the spread of the disease, particularly to infants and young children, who are more vulnerable to serious pertussis-related complications or death.

Sanofi Pasteur, the vaccines business of the Sanofi-Aventis Group (NYSE: SNY), announced that FDA's Vaccines and Related Biological Products Advisory Committee recommended licensure of its Adacel vaccine for protection against tetanus, diphtheria and pertussis in adolescents and adults aged 11-64 years.

GlaxoSmithKline (NYSE: GSK) announced that its booster vaccine candidate, Boostrix, received a unanimous favorable recommendation from the same committee. If approved, Boostrix would add a pertussis component to the routine tetanus/diphtheria booster currently recommended for adolescents.

Currently, there is no pertussis vaccine approved for use in the U.S. for children seven years of age or older. Immunity from childhood vaccination generally wears off after five to 10 years, leaving many adolescents susceptible to this highly contagious disease.

Most Cases Occur in Adolescents and Adults

Adacel is the first vaccine booster to address pertussis protection across a wide range of ages, including adolescents and adults, says Sanofi. These age groups are at a growing risk of contracting and transmitting whooping cough.

The number of reported cases of pertussis continues to rise at a rate of great concern to the public health and medical communities. The US Centers for Disease Control and Prevention (CDC) has received 19,000 case reports for 2004, a nearly 40 percent increase over 2003, and the highest number in four decades. Various studies indicate that the actual number of pertussis cases is many times greater than what is reported.

Approximately two-thirds of all cases occur in adolescents and adults. Although pertussis in adolescents and adults is often thought of as relatively mild, many in these age groups who contract the disease experience prolonged coughing, vomiting, missed school or work, and various complications.

Easily Transmitted to Infants

Due to similarities of symptoms, pertussis initially may be mistaken for other viral illnesses, such as bronchitis, influenza or even the common cold. In fact, it is within the first two weeks, often before a noticeable cough develops, when pertussis is most contagious.

Additionally, pertussis is easily transmitted to unimmunized or partially immunized infants and young children who are more vulnerable to serious pertussis-related complications or death. In effect, preventing pertussis in adolescents and adults could provide another means of preventing the spread of the disease, particularly to infants and young children.

"The dramatic increase in pertussis and the growing number of outbreaks are a critical reminder that we need to bring this serious disease under control," says David R. Johnson, MD, MPH, director, scientific and medical affairs, Sanofi Pasteur.

Four Adacel Studies Reviewed

Although the FDA is not bound by the Advisory Committee's recommendation, the agency considers it carefully when deciding whether to license a vaccine for marketing.

In making its recommendation, the FDA Advisory Committee reviewed the results of four principle clinical studies that included more than 7,200 individuals who were evaluated for safety.

The immunogenicity profile of Adacel vaccine was documented in a randomized subset of participants enrolled in the studies. Across the four trials, a total of 4,342 Adacel and Td vaccine recipients were evaluated for their immune responses to vaccination.

Adacel vaccine currently is licensed and marketed in Canada and Germany.

Boostrix Induces Higher Antibody Levels Than DTaP

In making its recommendation in favor of GlaxoSmithKline's Boostrix, the FDA Advisory Committee reviewed several clinical trials that included safety and immunogenicity data from one pivotal trial, which studied Boostrix in more than 3,000 adolescents in the United States, aged 10 to 18.

The Phase III clinical trial showed Boostrix to be comparable to a US- licensed Td vaccine [Tetanus and Diphtheria Toxoids] with regard to overall safety and immunogenicity.

In addition, the use of Boostrix induced anti-pertussis antibody levels, which were statistically higher than those observed in infants following primary immunization with a DTaP vaccine (Infanrix) [Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine Adsorbed] in whom efficacy against pertussis disease was demonstrated in a previous study.

"Adolescents are an important reservoir for the disease and often the source of infection for infants," notes Dr. Colin Marchant, adjunct associate professor, Boston University School of Medicine, Boston, Massachusetts.

"Adding pertussis to the current tetanus and diphtheria booster shot for teens is a logical strategy to prevent this disease in adolescents -- without additional injections -- and may help reduce the risk of transmission to infants in whom pertussis can be deadly," Dr. Marchant adds.