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Recovery during the convalescent stage can take weeks to months, and subsequent respiratory infections can lead to paroxysmal coughing. Adolescents and adults often have milder disease without the characteristic whoop and can transmit the illness undetected to the unimmunized or underimmunized.²

Laboratory confirmation of B. pertussis can be difficult, because it doesn’t grow in a standard culture medium, and a specific request for testing is required.

A nasopharyngeal swab obtained with a Dacron or calcium alginate swab is optimal. The organism rarely is isolated in the blood.³

Prevention priorities

Although pertussis can occur at any age regardless of immunization history, primary prevention through vaccination is the most effective strategy in controlling the disease.

In the early 1940s when the vaccine was first introduced, an average of 175,000 cases were reported per year in the United States. Annual incidence gradually decreased to an average of 2,900 from 1980 to 1990. By 2002, however, case numbers increased to 9,771. This was the highest number of reported cases since 1964. This number may be influenced by advancing laboratory technologies, better recognition of the illness among older age groups, improved reporting to public health entities, and the apparent three- to five-year cycle that has been observed with pertussis.²

The DTP vaccine, which protects against diphtheria, tetanus, and pertussis, has been a pediatric mainstay since the 1940s. In the 1970s, it came under scrutiny as a possible precursor to adverse events, such as brain damage. Countries that have decreased vaccination efforts have experienced a resurgence of pertussis. (See “Impact of Antivaccine Movements” sidebar.) Although the presumptions of toxicity are not supported by data, the whole cell vaccine composed of formalin-inactivated B. pertussis was replaced by a more purified acellular vaccine (DTaP), which has been available since 1991.^3,4

The vaccination is part of a series and is licensed only for children younger than age 7.⁴

Contraindications to the vaccine include an immediate anaphylactic reaction to the initial dose or an acute, severe neurologic reaction to the first dose occurring within seven days that does not resolve in 24 hours.

Other events, such as temperature elevation of 105 F or more; a hypotonic-hyporesponsive episode (HHE), where there is an acute diminution of sensory awareness or unconsciousness accompanied by pallor and muscle hypotonicity; persistent crying for three or more hours; or short-lived convulsions within 48 hours of a first dose are no longer considered contraindications to further vaccination.

They are precautions to be considered, but the benefit-risk ratio should be carefully considered for each individual.⁴ A vaccine information sheet developed by the Centers for Disease Control and Prevention for parents can be found at www.cdc.gov/nip/publications/vis/vis-dtp.pdf. Local reactions at the site and mild systemic reactions such as fever, drowsiness, fretfulness, and anorexia are common but usually short-lived and manageable.

Treatment should be with an aspirin-free product to avoid the potential for the development of Reye’s syndrome.⁴