Tetanus/Diphtheria/Pertussis Booster Questioned

[natesman1988]

Boostrix, Adacel Tdap Boosters Are Effective, Post-Marketing Studies Needed, Committee Says
FDA AdvisoryCommittee.com
Posted: Wednesday, March 16, 2005
URL: Http://www.fdaadvisorycommittee.com/FDC/AdvisoryCommittee/Committees/Vaccine
s+and+Related+Biological+Products/031505_Tdaps/031505_TdapR.htm


Postmarking safety and effectiveness monitoring would be needed for two
pending tetanus/diphtheria/acellular pertussis booster vaccines in
individuals who received only acellular pertussis vaccines as children, an
FDA advisory committee said March 15.

The Vaccines & Related Biological Products Advisory Committee voted 13-0
that available data are adequate to support the effectiveness and safety of
both GlaxoSmithKline's Boostrix and Sanofi Pasteur's Adacel.

However, the committee voiced concerns about use of the Tdap vaccines in
patients who are primed with a full course of acellular pertussis vaccine
during childhood.

Children in the companies' trials received either a full or partial course
of whole-cell pertussis vaccine, but whole-cell vaccine is no longer
administered in the U.S.

National Vaccine Program Office Director Bruce Gellin asked the companies
and FDA about plans to assess the vaccine once the patients receiving the
product move from a cohort of "whole-cell, either entirely or in part, to a
cohort that is going to be increasingly and entirely acellular." Gellin
served as a temporary voting member at the committee meeting.

Committee member Monica Farley (Emory University) agreed on the need for
"follow-up on those who've had the entire primary series with the acellular
product," to evaluate whether there is any impact on the boosters'
effectiveness.

Sanofi is seeking approval for use of Adacel in individuals 11-64 years old;
GSK is proposing use of Boostrix in patients 10-18 years old.

Despite their proposed indications as booster shots in adolescents and
adults, committee members expressed concern about the two Tdap vaccines'
impact on the primary vaccination process in childhood.

The GSK and Sanofi vaccines would probably be used clinically as a primary
series as well as a booster series, Emory University's David Stephens said.
Stephens served as a temporary voting member on the committee.

"Obviously, we're looking at a whole-cell pertussis background, but I'm more
into the mixing and matching of these acellular products," he said.

The committee's unanimous vote was a recommendation on effectiveness, rather
than efficacy. The panel edited FDA's questions before deliberation,
deciding to replace the word "efficacy" with "effectiveness."

"I'm a little bothered that we're being asked to vote on efficacy where, in
fact, we were presented no data on efficacy," committee member Philip
LaRussa (Columbia University) said.

"I'm just worried that as the word 'efficacy' filters into the proceedings
of the committee, people are actually going to start to believe that we
looked at efficacy data," he said.

There is no accepted serologic or laboratory correlate of clinical efficacy
for pertussis booster vaccines. In 1997, the advisory committee determined
that a clinical endpoint pertussis efficacy study is not required for Tdap
licensure for adolescents or adults.

Instead the companies are seeking approval for the boosters based on
non-inferiority studies comparing serologic results in infants and
adolescents.

There are currently no pertussis vaccines approved for use in adolescents or
adults in the U.S.

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