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This article was revised after it was printed in the May-June 2005 FDA Consumer to include information about a pertussis vaccine approved by the FDA for adolescents.
By Carol Rados
With the number of reported outbreaks of whooping cough (pertussis) on the rise in the United States, the Centers for Disease Control and Prevention (CDC) says there is a need to protect adolescents and adults, as well as children, against this highly contagious respiratory infection.
Commonly thought of as a childhood illness, pertussis actually affects people of all ages. According to the CDC, 5,000 to 7,000 cases are reported in the United States each year. Moreover, pertussis has been increasingly reported among adolescents and adults in the last several years. This is important because those who have a cough may not realize that they have pertussis and may be the primary source of infection for infants, who have the greatest risk of dying from the disease.
While there is no lifelong protection against pertussis, immunization by vaccine is the best preventive measure available. Vaccines currently licensed by the Food and Drug Administration to prevent the disease and reduce related illness and death are available for children up to age 7, and for adolescents between 10 and 18. The children's vaccine is part of a routine series of childhood immunizations called diphtheria-tetanus-acellular pertussis (DTaP) that is strongly recommended by the National Immunization Program at the CDC. It is administered in five doses, given at 2, 4, 6, and 15 to 18 months of age, and between 4 and 6 years. All five doses are recommended for maximum protection.
The adolescent vaccine, approved in May 2005, has the same components as the DTaP vaccine for infants and young children, but in reduced quantities.
Although most infants in the United States are immunized against pertussis, this immunity usually fades as a person enters adolescence or early adulthood. Health officials at the CDC say that preventing transmission of the disease to very young infants is critical because they are not old enough to be fully immunized. The CDC says that between 1996 and 2004 the majority of pertussis patients were either too young to have the required vaccine series or too old to have been immunized.
Researchers hope to change that. New vaccines, particularly one for adults, could help to reduce the incidence of pertussis in young infants as well by decreasing their exposure to the bacteria.
Pertussis is a respiratory system infection caused by the bacterium Bordetella pertussis. It is characterized by severe coughing spells that may end in a "whooping" sound when the infected person inhales. The first symptoms are like a cold-sneezing, runny nose, nasal congestion, slight fever, and a dry cough that may get worse at night. But unlike a cold, whooping cough sticks around, and within two weeks the symptoms get worse. A person can have fits of coughing that seem to go on and on. Severe coughing can lead to vomiting and may make it hard for a person to eat or drink. Because adults and adolescents with pertussis may have milder symptoms, they usually don't know they have the disease.
People get pertussis by breathing in tiny droplets released into the air by an infected person's cough or sneeze. Once inside the airways, pertussis bacteria produce toxins that interfere with the respiratory tract's normal ability to eliminate germs. The bacteria also produce chemicals that cause inflammation, damaging the lining of the breathing passages.
Pertussis can last for several weeks or longer. It is typically treated with antibiotics; however, unless started early in the course of the illness, antibiotics do little to help the coughing illness. Patients with this disease are advised to avoid contact with anyone, particularly infants and children.
Without vaccine protection, people can easily contract and transmit this infectious disease. Routine immunization with pertussis vaccines has greatly reduced illness and deaths associated with the disease.
Most vaccines contain a weakened (attenuated) or killed (inactivated) form of disease-causing bacteria or viruses, or components of these microorganisms, that triggers a response by the body's immune system. They stimulate the body to make antibodies-proteins that specifically recognize and target the bacteria and viruses and help eliminate them from the body.
The search for a vaccine to prevent pertussis began in 1906, when two French bacteriologists isolated the bacterium responsible for infection. In the 1940s, experimental vaccines were successful in producing a protective immune response in humans. The first pertussis vaccine was licensed for use in the United States in 1948. These early pertussis vaccines were made from killed whole bacteria. According to the National Institutes of Health (NIH) and the CDC, subsequent widespread use of the vaccine contributed to a dramatic decline in the U.S. incidence of the disease, which reached an all-time low of just over 1,000 cases in 1976.
Although the vaccine was extremely effective in controlling pertussis, it was associated with some serious side effects, such as fever and rare seizures that eventually discouraged some parents from having their children immunized. In addition, the number of pertussis cases was increasing in the United States by the early 1980s. In response to these concerns, the public health community set out to develop an improved vaccine that would be equally effective, but associated with fewer side effects.
Encouraging findings in the late 1980s and early 1990s eventually led to the 1996 licensing of the DTaP vaccine series. The acellular pertussis vaccine uses a form of the bacterium without its cell wall that doesn't cause the adverse that the whole-cell predecessor did. According to the CDC, DTaP is a safer version of the older vaccine DTP, which is no longer used in the United States.
The collaboration of the FDA, the NIH, the CDC, and the pharmaceutical industry helped expedite approval of the children's DTaP vaccine series. The public health community is looking to further improve pertussis vaccines by finding ways to reduce the number of doses required in childhood and to lengthen the period of immunity produced by the vaccines.
It is important to understand the burden of pertussis disease in various age groups. Protecting infants from its severe form and diagnosing the disease in a timely, accurate manner are important factors in controlling future outbreaks.
The Centers for Disease Control and Prevention says that people can better protect themselves and others from contracting whooping cough by: