POST 00847E : SEEKING YOUR OPINION 26 October 2005
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Michel Zaffran (mailto:[email protected]) from WHO requests your opinions on
the topic below. If you wish your opinion posted, please send a copy to
TechNet.
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COMBINATION VACCINES, LYOPHILIZED VACCINES, DILUENTS AND VVMS
1. WHO recommendation is that lyophilised vaccines should be discarded 6
hours after reconstitution or at the end of the immunization session for
which they have been reconstituted, whichever comes first. Indeed,
lyophilized vaccines do not contain preservatives and there is therefore a
high risk that they could be contaminated and become a very good medium for
bacterial or other pathogens growth, thus a hazard to the vaccine recipient.
2. When VVMs were introduced on lyophilised vaccines (measles, BCG, Yellow
Fever), manufacturers were requested to put it on the cap of the vial so
that, when the vaccine is reconstituted, the VVM is thrown away. This way
the health worker cannot read the VVM and use it as an indication that the
vaccine can be kept longer.
3. With the advent of combination vaccines, we are now being faced with
situations where some lyophilized vaccine (Hib) can be reconstituted with a
liquid vaccine containing a preservative (DTP or DTP-Hep B). The question
has come up of whether there would be a simple way to advise health workers
that, in some specific case, they can keep the reconstituted vaccine vial,
(following the conditions of the Multi-Dose Vial Policy) and not run the
risk of confusion created by this situation where :"some lyophilized
vaccines can be kept after reconstitution and others cannot" ….
Provided laboratory contamination studies confirm that indeed the Multi-
Dose Vial Policy applies to these cases, i.e. lyophilized vaccines
reconstituted with another vaccine containing preservatives (example of
DTP-HepB with lyophilised Hib for instance), the proposal we would like
your feedback on is whether this can be done by asking that the VVM be
affixed on the label of the lyophilized vaccine.
So, for instance, in the case of Hib lyophilized vaccine reconstituted with
a DTP-Hep B liquid vaccine, the VVM on the Hib vial would be on the label,
it would match the stability of the reconstituted product (DTP-HepB- Hib)
and the multi dose vial policy could apply on the fully liquid
reconstituted vaccine. The advantage would be that the Multi dose vial
Policy could be applied to 10 dose vials of combination vaccines thus
making it potentially more economical than singe dose presentations
Of course, the change would only apply to those vials of vaccines which are
supplied through UN agencies and prequalified for reconstitution with
preserved vaccines and would be based on 1) the data on the effectiveness
of the preservative in the reconstituted vaccine and 2) the data on the
stability of the reconstituted vaccine.
Risks that we consider may be possible (may not be exhaustive)
* The Hib vial is used with another diluent than the DTP-HepB with
thiomersal (the risk is similar as for any lyophilized vaccine of a wrong
diluent being used)
* The final reconstituted product is put back into the DTP-HepB vial
and the wrong VVM is therefore used to monitor heat exposure (unlikely
since this would go against usual practice)
* Health workers do get confused by the new message and keep other
lyophilized vaccines beyond six hours after reconstitution (the risk that
this happens may be low but outcome could be very serious if this happens) .
* Health workers do not pay attention to VVM or do not know what it is
and discard the vial after 6 hours anyway (The risk is of increased wastage) .
A question is also raised as to what text will be on the label of the Hib
vial - since it will contain initially Hib vaccine, the label will normally
say "Hib" but the vial will also eventually contain the reconstituted
DTP-HepB-Hib vaccine which can in principle be kept for several days -.
We would appreciate your views on the above suggestion, any pro or con of
moving in that direction would be appreciated
Note that this particular question raises many other questions related to
the current situation in the field with lyophilized vaccines where vials of
diluents are very seldom available in quantities matching the lyophilized
vaccine vials.
Since the two vials are not packaged together, the likelihood that they end
up together in the health center is small.
We have many reports of such mismatch.
Could readers of the TechNet Forum also comment on whether they have
noticed similar issues with combination vaccines (DTP-HepB + Hib or DTP+ Hib)
Michel Zaffran
Coordinator, Access to Technologies
Immunization, Vaccines and Biologicals
WHO Family and Community Health
Geneva, Switzerland
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