Oral Polio Delivered Safely Without Icepacks in Recent Study
by Ariane Halm, EPIET (European Programme for Intervention Epidemiology Training), and Olivier Ronveaux, WHO
Optimizerecently completed a study with the World Health Organization (WHO) Country Office and the Ministry of Health in Mali to determine the feasibility of using oral polio vaccine (OPV) out of the traditional cold chain temperatures during a National Immunization Day campaign. In four health areas, thirty-nine vaccination teams successively transported OPV in the vaccine carrier with icepacks (keeping the vaccine at cold chain temperatures) and without icepacks in order to evaluate the outcome of transporting the vaccines without ensuring a continuous cold chain. The practice at ambient temperature was limited to a maximum of one outreach day.
The study concluded successfully, with no major problems or deviations to the methodology. A total of 14,913 children were vaccinated in the study areas. About half of the vials (54%) were transported in vaccine carriers without icepacks, and all of these vials were still usable as indicated by the vaccine vial monitors at the time of the last administered dose despite ambient temperatures ranging from 25° to 40°C (mean of 27°C). Wastage rates were lower for the vials traveling without icepacks because they did not have the problems usually caused by melting ice and icepacks (e.g., moisture on the label making it unreadable, vials contaminated with water, etc.). Health workers also reported that the ambient temperature transport facilitated preparation and implementation activities, reduced the weight they needed to carry, and required less time (possibly resulting in more children being immunized). Direct costs for the ambient temperature transport were lower, primarily because icepacks did not need to be resupplied.
The study suggests that ambient temperature transport of OPV may provide a safe alternative in geographically challenging settings or where cold chain material cannot be made available. However, vaccines transported in ambient temperature must come with vaccine vial monitors and staff must be adequately trained to interpret them.
This study adds evidence to the possibility that ambient temperature supply chains may be one of the solutions to address constraints in cold chain space that are likely to occur with new vaccine introduction.
A paper on this experience is being submitted for publication in a scientific journal.
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Photo Courtesy : Olivier Ronveaux
The purpose of this study was to add to the body of evidence that is being generated to determine whether new policies and guidelines can be developped on the use and storage of vaccines at higher temperatures than the traditional 2-8°C , but still under controlled conditions. Such guidelines have not so far been issued by WHO but work is underway and is being discussed by the WHO Technology and Logistics Advisory Committee (TLAC). Several countries however have already initiated strategies which take vaccines such as Hepatitis B beyond the existing cold chain to increase outreach for the delivery of the birth dose.
To specically address your question, the correlation between the potency of OPV and the VVM reading has been studied by the NIBSC in the UK aat the request of WHO. The report of this study was published under the reference WHO/V&B/99.11 (http://whqlibdoc.who.int/hq/1999/WHO_V&B_99.11.pdf)
regards
Michel Zaffran
I very much agree with the recommendation that we should focus on heat stable vaccines. This, in fact, is the focus chosen in the work that is currently on-going through the WHO-PATH (Optimize) collaboration looking for instance at hepatitis B vaccine.
The OPV example however shows that, even with a very heat labile vaccine such as OPV, if appropriate precautions are taken, if the VVM is well understood and well used, then some level of CONTROLLED flexibility can be added to simplify the logistics of campaigns.
I would like to stress however that we have simply documented an existing practice and shown that it was technically valid and brought benefits to the health workers . Our intent is not to propose that new policies be developped for vaccines that are very heat sensistive
Regards
Michel Zaffran (Senior Adviser, WHO/IVB and Director WHO/PATH project Optimize)
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