POST 00855E : COMBINATION VACCINES, LYOPHILIZED VACCINES, DILUENTS AND VVMS
Follow-up on Posts 00847E and 00852E
13 November 2005
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This posting contains two contributions. The first is from Oleg Benes
(mailto:
[email protected]) from Moldova. The other, originally in French,
is from Philippe Jaillard (mailto:
[email protected]) from Bénin. Both
express serious concerns.
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Dear Michel,
I think the topic you have raised is very important.
I understand the economical rationale for applying the MDVP for
reconstituted pentavalent vaccine and the opportunity to reduce costs and
contribute to the sustainability of country programmes.
The same time I am convinced that only simple messages and rules have the
chance to be applied in a satisfactory and safe manner in the field.
We all know how often people in the field are challenged by getting a large
variety of packages, labels and presentations for traditional vaccines
(provided by different vaccine manufacturers), language/translation issues
(the vaccine insert is part of the package box, while vaccine is often
supplied by vials). Implementation of each additional antigen makes this
picture more and more complex.
Based on my observations the current MDVP knowledge and practice in the
field is far from satisfactory, even in countries promoting and using it
for many years. One of the simplest ways to promote the message was: you
reconstitute vaccine - you use it within 6 hours. If the vaccine comes
liquid, ready for use, you may use it for a longer time (one month) subject
of a) VVM status, b) expiry date, c) cold chain (when no VVM), d) no risk
of contamination.
Now, we have to change the mind of all workers in the system, and it may
not be an easy task.
Teaching that some reconstituted vaccines may be used only for 6 (4) hours
while others may be used for a longer time will complicate a lot our message.
I consider that risks related to the failure of the policy are very high.
Because based on the penta-valent example people may extend this policy to
other lyophilized vaccines. And consequences may be so dramatic.
So, I would suggest to try to experience and assess in the field potential
implications for this policy change on local knowledge and practice.
The next point is related to using the VVM as a trigger for deciding
whether to use the vaccine only during one session, or for an extended
time. I would not agree with that. Because the VVM is a temperature
exposure indicator and it has nothing to do with risks of contamination of
an opened vial. We should keep ours message simple, another way we may risk
to compromise appropriate understanding and use of VVMs.
Finally I do not like at all the concept of lyophilized pentavalent, when
one vaccine is used as diluent for another one. This, again, breaks the
rules that vaccines should never be mixed with one syringe and that
lyophilized vaccines should not be reconstituted with liquid vaccines.
I wonder whether there are some studies on the impact of the implementation
of pentavalent on knowledge and practice of health workers related to
vaccine safety issues.
With best regards,
Oleg Benes,
Medical Epidemiologist ,
National Center of Preventive Medicine
Chisinau, Republic of Moldova
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Hello,
Just some comments and reflections on Michel Zaffran’s message.
The VVM and the MDVP both contribute to costs reduction, sometimes at the
expense of vaccine quality just because these tools are not properly used.
As for the tetravalent or pentavalent vaccines with a Hib lyophilised
component, the suggestion to have a VVM placed on the vial of Hib looks
very attractive. However, since the vaccine is reconstituted with DPT or
liquid DPT-HepB, it is necessary to have also a VVM on the vial with liquid
vaccine. Otherwise there is a risk of adding a product of uncertain quality
(DPT or DPT-HepB with no VVM) to a quality product (Hib with unturned VVM).
Is there any plan to affix a VVM on liquid vaccines vials? If this is the
case, will the message indicating that both vials should have
simultaneously unturned VVMs at the moment of reconstitution, be easily
perceived?
On the other hand, liquid DPTvaccine is sensitive to freezing and the HepB
vaccine is destroyed after a short exposure to negative temperatures. A
study done by a trainee from the EPIVAC programme has exposed a lot of
inadequacies in HepB vaccine conservation in his district (in 55% of health
centres, HepB vaccines had been exposed to temperatures below -5 C for 5
days). This leads to believe that such vaccines have lost their potency.
This is not an exceptional case and knowledge of the real quality of
freeze-sensitive vaccines before administration, is generally insufficient.
In such situations, the presence of VVM on the vial of Hib before
reconstitution could lead the health worker to believe, that he is
administering a good quality vaccine, regardless of the quality of the
liquid product.
Before placing VVMs on Hib vials, I think it is necessary to improve the
quality of vaccine conservation (equipment, staff competence) first by
developing, in countries, the knowledge of this quality of conservation and
secondly, to improve the way health workers use wastage reduction tools
(mastering of VVMs and MDVP –the same study shows that 57% of health
workers do not know MDVP).
Regards,
Philippe Jaillard,
Immunizations Logistics Consultant, AMP
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