Pertussis Vaccination in Adults ≥65 Years of Age

The Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) has released its recommendations for the use of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine in adults ≥65 years of age. The report appeared in the Morbidity and Mortality Weekly Report [2012;35:468-470].

In October 2010, despite the lack of an approved Tdap vaccine for this population, ACIP recommended that unvaccinated adults, ≥65 years of age, who had close contact with an infant should be vaccinated with Tdap, and that other adults ≥65 years of age could also receive the vaccine. In July 2011, the FDA approved expanding the age indication for Boostrix^® (Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine, Adsorbed) to ≥65 years of age and in February 2012, ACIP recommended Tdap for all adults ≥65 years of age. This latest recommendation supersedes previous Tdap guidelines for adults ≥65 years of age.

Boostrix and Adacel^® (Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine, Adsorbed) are the 2 Tdap vaccines available in the United States. Only Boostrix is approved for the population ≥65 years of age; however, ACIP included Adacel in the preparation of the latest guidelines.

The actual burden of pertussis in adults ≥65 years of age is unknown. Challenges to correctly diagnosing and reporting the disease include (1) under-recognition of pertussis as a cause for cough illness, (2) atypical presentation of symptoms, and (3) a low index of suspicion among providers.

There have been only a few studies on the burden of pertussis in adults ≥65 years of age. Among reported prospective studies, the estimated incidence of pertussis ranged from 66 to 500 cases per 100,000 persons per year. Reported pertussis incidence ranges from 1 to 5 cases per 100,000 in adults of similar age ranges; according to the CDC report, this 70-fold to 100-fold difference suggests that actual pertussis incidence in older adults is much higher than reported. In establishing the current vaccine recommendations, ACIP supported the conclusion that the actual burden of pertussis in adults ≥65 years of age is likely to be at least 100 times greater than what has been reported.

ACIP reviewed 2 unpublished cost-effectiveness models (developed independently by GlaxoSmithKline and the CDC). Both models were developed to determine the epidemiologic and economic impact of Tdap vaccination in adults ≥65 years of age; both studies demonstrated that a dose of Tdap for older adults resulted in a moderate decrease in the number of cases and outcomes (outpatient visits, hospitalizations, and deaths), which might, according to the CDC report, “represent a cost-effectiveness intervention.”

The ACIP recommends that all adults ≥19 years of age who have not received a dose of Tdap receive a single dose. The vaccine should be administered regardless of the interval since the last tetanus or diphtheria toxoid-containing vaccine. Following the initial dose of Tdap, all adults should receive Td for routine booster immunization against tetanus and diphtheria, according to previously published guidelines.

The report stated that providers should vaccinate adults ≥65 years of age with the Tdap they have available. When possible, Boostrix should be used; however, ACIP concluded that either vaccine administered to an adult ≥65 years of age is immunogenic and would provide protection. “A dose of either vaccine many be considered valid,” the report concluded.