ATLANTA – The tetanus-diphtheria-acellular pertussis vaccine should be given to adults aged 65 years and older, according to recommendations from the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices.
The recommendation, backed by a 14-1 vote among ACIP members, is expected to go into effect when the CDC publishes the guidance, along with other guidance related to use of the adolescent/adult formulation of the tetanus-diphtheria-acellular pertussis vaccine (Tdap).
Of the two currently licensed Tdap vaccines, only GlaxoSmithKline’s Boostrix is approved for adults aged 65 and older. Efficacy data for the other one, Sanofi-Pasteur’s Adacel, had been submitted to the Food and Drug Administration but did not meet immunogenicity end points, the FDA’s representative, Dr. Wellington Sun, told the committee.
The ACIP recommendation will express a preference for use of Boostrix in the 65+ age group but is expected to state that Adacel is acceptable and preferable to delay of vaccination if Boostrix is not available. There were differences of opinion among committee members about whether to express a preference or not, and the exact language for the recommendation was still to be worked out at the time of the vote.
Current recommendations call for a single dose of Tdap for adults aged 19-64 years. Previously, the vaccine had only been recommended for adults 65 and older who were in close contact with an infant less than 12 months of age. With the current vote, ACIP also recommended elimination of the "decennial" interval that had previously been applied to the tetanus-diphtheria vaccine, so that a single dose of Tdap can be given to any adult who has not previously received it, regardless of interval since the last Td, said Dr. Jennifer L. Liang who explained the ACIP Pertussis Vaccines Working Groups’ deliberations.
Dr. Gregory Poland
Liaisons from the American College of Physicians (ACP) and the American Academy of Family Physicians (AAFP) said they supported the vote. "I think the important thing that we did today was in essence make a universal use recommendation for Tdap in adults. Before, it was full of provisos that clinicians couldn’t remember, sort of like the flu [vaccine] story. We’ve made it easy for clinicians by saying every adult deserves a dose of Tdap," ACP liaison Gregory A. Poland said in an interview.
However, "There are unknowns yet. We don’t know the duration of efficacy or the exact level of efficacy, particularly in older adults. Those are data needs that we have," noted Dr. Poland, the Mary Lowell Leary Professor of Medicine and Infectious Diseases at the Mayo Clinic, Rochester, Minn.
According to AAFP liaison Dr. Jamie Loehr, owner of Cayuga Family Medicine, Ithaca, N.Y., "The [AAFP] will review this, and most likely support it as it has in the past. On a practical level, it will be much easier for family physicians to have a blanket immunization recommendation rather than having to pick and chose."
Surveillance data suggest that the incidence of pertussis overall among adults older than 65 in the U.S. ranges from 2.5/100,000 in those aged 65-69 years to 0.8/100,000 in those aged 85 years and older. However, reported rates for adults are believed to be greatly underestimated since adults often don’t exhibit the typical paroxysms, inspiratory whoop, and post-tussive vomiting seen in infants with pertussis. Indeed, data from Australian surveillance and from published studies on varying age groups, some including adults beyond age 65 years, suggest that the incidence actually ranges from 66 to 507 cases/100,000 population, the CDC’s Dr. Anna Acosta told the ACIP.
Dr. Jamie Loehr
Girishanthy Krishnarajah of GlaxoSmithKline presented a cost-effectiveness analysis of a one-time Boostrix vaccination among a cohort of U.S. residents aged 65 and older, in which the cost per case averted ranged from $416 to $10,413, depending on the pertussis incidence level. The cost per quality-adjusted life year (QALY) ranged from $13,260 to $332,218, also depending on incidence. When the pertussis incidence in people aged 65 years and older exceeded 110/100,000, the incremental cost-effectiveness ratio falls below $50,000/QALY, the generally accepted cost-effectiveness threshold, she said.
A CDC cost-effectiveness analysis produced similar results, according to Dr. Acosta.
Data suggest that safety and tolerability of Tdap in older adults is similar to that of the Td vaccine. While there are no efficacy data available specifically in the 65+ age group, data suggest that "older adults mount an immune response, likely to provide protection," the CDC’s Dr. Liang said.
Several ACIP members expressed concern that efficacy data were not available, but voted in favor of the recommendation regardless. Dr. Jeffrey Duchin was the sole committee member who cast a vote against the recommendation. "I would have liked to have seen more data on efficacy in the older population. It was assumed in the models. I would like to see more studies," Dr. Duchin, a professor of medicine at the University of Washington in Seattle, said in an interview.