Underreported and on the rise: Whooping cough

Pertussis, known also as whooping cough, is a highly communicable infectious disease of the respiratory tract caused by airborne exposure to Bordetella pertussis, a gram-negative bacillus. In addition to the coughing and choking spells that make breathing difficult, major complications-most common among infants and young children-include hypoxia, apnea, pneumonia, seizures, encephalopathy, and malnutrition. In a teleconference conducted recently by the National Foundation for Infectious Diseases, several physicians discussed the new adult recommendations for pertussis booster vaccinations.

Katrina Kretsinger, M.D., a medical epidemiologist and lieutenant commander with the U.S. Public Health Service, said, "Pertussis is the most poorly controlled preventable disease in this country. It is typically considered a childhood disease; thus many adult providers may not think of pertussis at all, even when an adult presents with a very typical classic case."

Pertussis can be especially serious for infants less than a year old; it may even be fatal. Prior to the 1940s, pertussis was a dreaded disease that claimed thousands of lives-mostly infants and young children. However, with the availability of childhood vaccines, its incidence has decreased. But even the reported occurrence of pertussis cases is not a good representation of the actual number. In 2004, approximately 26,000 cases of pertussis were reported in the United States, with adults accounting for a third of those cases. Kretsinger, along with William Schaffner, M.D., professor and chairman, department of preventative medicine, Vanderbilt University School of Medicine, reported an estimated 600,000 cases of pertussis every year in the adult population. The underreporting of the disease is likely due to the fact that some states report only culture-positive cases, making it hard to predict the true burden of the disease.

The Food & Drug Administration has licensed two new vaccines for a single booster immunization against pertussis, in combination with tetanus and diphtheria (Tdap). Boostrix (GlaxoSmithKline Biologicals) was licensed on May 3, 2005, for use in adolescents 10-18 years old. Adacel (Sanofi Pasteur) was licensed on June 10, 2005, for persons 11-64 years of age. These are the first pertussis booster vaccines to be licensed in adolescents and adults. Recently, the CDC Advisory Committee on Immunization Practices (ACIP) voted that adults from 19 to 64 years of age should be vaccinated with the Tdap vaccine. Under the new ACIP recommendation, Tdap would replace the tetanus-diphtheria vaccine now recommended and used as an adult booster.

The new vaccine would reduce the risk of transmitting the disease to infants. Adults can transmit the bacterium to infants too young to start the vaccine or children who have not completed the series, said Schaffner.

Russell Steele, M.D., professor and vice chairman of pediatrics at Louisiana State University School of Medicine, said the impact on infants is of greatest concern, as they are more susceptible to death and complicated infections.

Pertussis is highly contagious, with up to 90% of susceptible household contacts developing clinical disease following exposure to an index case. "These new recommendations are highly vital to protecting both adults and children because of the high contagiousness," he said.

To prevent disease transmission, a community must be immunized. The first step is to vaccinate all children on time with the primary series of the vaccine. In Canada's four-year experience with the vaccine, the incidence of pertussis has decreased from 12 cases per 10,000 people to one case per 40,000 people. Kretsinger added that by stocking and administering the vaccine as indicated, discussing the importance of the vaccine with patients, and asking patients if they are up to date on their tetanus vaccine or if they are in close contact with infants, healthcare providers can play an active role in reducing the incidence, and preventing the spread, of pertussis.

The Author is a healthcare writer based in northern New Jersey.