Interchangeability of various combination vaccines
PRACTICAL ISSUES IN THE USE OF COMBINATION VACCINES
Interchangeability
It is unrealistic to expect that the same vaccine will always be available for each child at the time of each vaccination, given bulk vaccine purchasing through competitive bidding. The situation is further complicated by the fact that 25% of children see at least 2 different healthcare providers for vaccination during the first 2 years of life and that children remain in publicly funded healthcare plans for 9 months, on average. 41 Different practitioners are likely to stock different combination vaccines, and it will not be feasible to stock all brands of each type of licensed monovalent or combination vaccine.
When multiple combination vaccines are available from several different manufacturers, practitioners will question whether the vaccines can be used interchangeably. This question is complex to answer even for monocomponent vaccines; getting definitive answers for multicomponent vaccines will be more difficult. For example a study to determine the interchangeability of the 3 conjugate Hib vaccines indicated for the infant primary series evaluated 5 of the 27 theoretically possible permutations of 3 vaccines and 3 injections. 42 Once we are faced with multiple combination vaccines, the likelihood shrinks that any particular substitution will have been studied explicitly. Indeed it has been suggested that the cost of evaluating all potential schedules using several different combination vaccinesfrom different manufacturers would be between $5 and $15 billion. 43
The ACIP has recognized certain vaccines as interchangeable, including IPV and HepB. 44 Conjugate Hib vaccines are also considered interchangeable, as long as three doses are given. 41 For vaccines lacking data regarding interchangeability of licensed products, such as DTPa and newer combination vaccines, 41, 45 the ACIP has recommended that the same product be used throughout the primary series. However, according to the ACIP recommendations, if the identity of the product previously used is not known or if the product is not available at the time of the child’s visit, then any licensed product appropriate to the child’s immunization status and requirements may be used. Although specific data supporting interchangeability would be desirable, there are no published data that demonstrate adverse consequences of switching during the primary immunization series from one brand to another for any type of vaccine. The imperative remains, “Do not miss a vaccination opportunity.”
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