NOTE: Updated version of the VPAT, version 1.03, posted on February 5, 2010
What is VPAT?
The vaccine presentation assessment tool (VPAT) is designed to model the logistical and financial impact of adding a new vaccine to an immunization schedule. VPAT was developed by Andrew Garnett through a project of the PATH Malaria Vaccine Initiative (MVI), with financial support from the Bill & Melinda Gates Foundation.
The VPAT was originally designed for malaria vaccines; it was subsequently extended for use with other new vaccines, with financial support from the GAVI Alliance.
The VPAT tool can be used in the following ways:
1. To help a manufacturer establish the most suitable format for a novel vaccine by comparing the impact of alternative presentations and packaging on a specific country’s vaccine supply chain. Typically this exercise will take place during early discussions between the public sector and the vaccine manufacturer before these critical manufacturing decisions have been finalized.
2. To assess the impact of adding a new vaccine to a country’s schedule, particularly when this vaccine is available on the market in alternative presentations.
3. To analyze the effect of substituting a new vaccine for an existing one in a specific country—for example, moving from a series of multi-dose single antigen vaccines to a single-dose combination vaccine.
The output from the tool will provide an analytical basis to support collaborative evidence-based discussions on these impacts, internally within the public sector, and externally with vaccine manufacturers and with target countries.
In the case of a novel vaccine, the desirable endpoint of this process is to ensure that the presentation for a new vaccine balances the following factors:
· Vaccine manufacturing and filling line capacity and restrictions.
· The need to minimize impact on country cold chains and waste streams.
· The need to minimize vaccine wastage whilst taking account of typical session size(s).
· The need to achieve the lowest possible overall cost per delivered dose.
· Acceptability of the vaccine presentation(s) to health workers, given the target population, schedule, and vaccination strategy.
VPAT's Analytical approach
VPAT’s analytical approach is based on a notional ‘fully immunized target group’ (FITG). The user defines a context-specific framework which takes account of the immunization schedules, average wastage rates, cold chain storage, transport infrastructure, etc. that are typical of the country(s) or region(s) where the target vaccine is to be deployed. Since national immunization programs and vaccine supply chain logistics are unique for each country, the results of the analyses may only be applicable to the particular country or countries assessed.
Collection of country-specific supply chain and immunization systems data is challenging; however, data from several countries has recently been collected. As manufacturers and global health individuals use the VPAT, supply chain information collected from various countries ideally may be shared and aggregated to allow for the development of a regionally or globally representative model.
Finally, the tool is intended to provide a ‘broad brush’ analysis at a national scale of the country or countries included in the study. It takes no account of detailed operational issues such as differential vaccine delivery strategies, variations in average session size and coverage in urban, rural and campaign settings, drop-out rates and other modifying factors which may be very significant at the local scale. Introducing such complicating factors into the model would require so many assumptions that the relatively simple conclusions that can be drawn from using the tool would be obscured.