Hélène Pora
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If there's one thing that avian flu is doing to benefit vaccine development, it is instigating the transition from egg-based,
to cell-based, technologies. Even without avian flu concerns, traditional flu vaccine production is a long and difficult
process, requiring that millions of eggs be ordered one or two years ahead of time. The 50-year old process also offers little
opportunity for ramp-up in the case of a pandemic or a major compliance failure. To compensate for some of these shortcomings,
many vaccine manufacturers are turning to disposable technologies to improve the safety and efficiency of existing processes.
Disposables eliminate the need for cleaning and cleaning validation. Discarding a device, without proving that it has been
sufficiently cleaned, is one step that both regulatory bodies and manufacturers are happy to eliminate. This is especially
true for vaccines, because vaccinating large, healthy populations carries much greater risks than treating relatively small
groups of people with conventional drugs. For manufacturers attempting to minimize the risks of vaccine batch contamination,
disposables provide an important avenue for enhanced safety.
DISPOSABLES ARE ECONOMICAL
The use of disposable technologies is particularly economical for campaign-based vaccine manufacture. Disposables ensure fast
set-up, they reduce the need for capital investment in stainless steel equipment, and require little work after use.
Single-use systems that the supplier pre-sterilizes and bundles together can further simplify set-up. With fewer opportunities
for operator error, disposable technologies also improve safety and production economics. Some disposables, such as bags,
also save space, because they lie flat and can be stacked before use. Unlike permanent storage tanks, disposable bags are
ordered on an as-needed basis to avoid excess unused equipment.
Figure 1. Disposable technologies can be used in many stages of vaccine production. Solid circles indicate ideal steps where
disposable technologies can be applied. Dotted circles indicate where technology is applicable, with hardware support.
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CELL-BASED VACCINE MANUFACTURING
Although new vaccines are still being developed using traditional egg-based technologies, the race to produce vaccines from
cell-based technologies is heating up with a non-egg production method projected to be on the market by 2008, according to
Gbola Amusa, a research analyst from Bernstein Research.1 While there are currently no cell-based vaccines beyond early clinical trial phases in the United States, Solvay Pharmaceuticals
has a cell-based flu vaccine approved for use in the Netherlands.
The use of disposables in egg-based vaccine manufacture can be seen as preparation for the transition to mammalian cell-based
development, where single-use systems are becoming more common. While single-use technologies can play a prominent role in
egg-based vaccine manufacture in the areas of filtration, storage, and at connection points, their use multiplies in cell-based
applications. More specifically, disposable technologies can be used for media preparation, clarification, buffer preparation,
capture, and polishing chromatography steps, filling in downstream processes, and for venting and cell harvesting in upstream
processes.
Disposable bioreactors are an example of the growing role of single-use technologies in upstream processing. Despite the availability
of increasingly large disposable bioreactors, the material strength of the cell bag and the ability to supply adequate mixing
remain a challenge. Although large volume (over 1,000 L) disposable bioreactors are probably a few years away, current offerings
are commonly used in smaller cell culture applications, as well as for growing seed innoculums while the large stainless tanks
are being prepared.
