Whooping cough is thought of as an illness from an earlier era, but it is on the rise in the United States.
Now a new study suggests that as many as 1 million cases could be prevented each year by routinely vaccinating teens and adults against the highly infectious respiratory disease.
The CDC reports that about 9,800 new cases of whooping cough were reported in 2002. Experts say the disease is common, but rarely suspected, in adults and adolescents.
“The underreporting of this disease is monumental,” says Joel Ward, MD, of the UCLA Center for Vaccine Research. “Physicians don’t even consider it when they treat adults for persistent cough.”
Childhood Immunity Often Wanes
Whooping cough, known medically as pertussis, is a highly contagious respiratory infection caused by the bacterium Bordetella pertussis that can cause coughing and choking fits.
It was a major cause of serious illness and death among infants and young children prior to the development of the pertussis vaccine in the early 1940s.
Today, children in the U.S. routinely get vaccinated before age 6. Protection typically lasts between five and 10 years after the last dose of vaccine is given.
Waning immunity is increasingly recognized as a cause of illness in teens and adults. But because whooping cough is often mistaken for other coughing-related conditions, the true incidence of the disease has not been known.
In the newly reported study, Ward and colleagues closely followed people between the ages of 15 and 65 who were or were not vaccinated against whooping cough. Immunization was found to be very effective, with just one case of whooping cough occurring in the roughly 1,400 vaccinated subjects over the next two years, compared to nine cases in those who were not immunized against the disease.
The study is reported in the Oct. 13 issue of The New England Journal of Medicine.
1 Million Cases
The study participants came from all over the country and were subjected to extensive medical testing each time they developed a coughing-related illness. This design allowed the researchers to estimate the countrywide incidence of whooping cough among adolescents and adults.
“One out of two people each year will develop a coughing illness that lasts at least a week, and we know that pertussis causes 1% to 5% of these illnesses,” Ward tells WebMD.
On the basis of their findings, Ward and colleagues estimate that about 1 million cases of whooping cough occur among teens and adults in the United States each year.
”This gives us our best understanding yet about the burden of this illness in adults,” whooping cough expert Scott Halperin, MD, tells WebMD.
Protecting adults against whooping cough is problematic because there are no guidelines for routine pertussis vaccination in adults. The researchers suggest that the vaccination of children between the ages of 10 and 19 may be a cost-effective way to start.
The CDC’s Advisory Committee on Immunization Practices is expected to consider the issue in upcoming meetings.
Whooping cough researcher Michael E. Pichichero, MD, tells WebMD that he believes the group will recommend routine immunization against whooping cough only for those at high risk or who are around high-risk populations. This is likely to include all health care workers, people with chronic lung conditions, and parents and other caregivers who have contact with children under age 6 months.
By Salynn Boyles, reviewed by Louise Chang, MD
SOURCES: Ward, J.I. The New England Journal of Medicine, Oct. 13, 2005; vol 353: pp 1555-1563. Joel Ward, MD, UCLA Center for Vaccine Research, Research and Education Institute, Harbor-UCLA Medical Center, Los Angeles. Scott A. Halperin, MD, department of pediatrics and microbiology and immunology, Dalhousie University and the IWK Health Centre, Halifax, Nova Scotia. Michael E. Pichichero, MD, University of Rochester Medical Center, Rochester, N.Y. CDC web site. National Center for Health Statistics web site.