Optaflu, a flu shot made in mammalian cell culture rather than embryonated chicken eggs, has just been recommended for approval by the European Commission's Committee for Medicinal Products for Human Use (CHMP).

At the moment all registered seasonal flu vaccines are made in eggs, a lengthy process which means it takes month to produce each batch of vaccine. This is the reason why the World Health Organization decides each February what three strains of the virus are likely to be the greatest threat the following winter, so manufacturers can tailor their production accordingly.

Using a cell-based production approach could slash the time it takes to produce the antigens used in the vaccines, potentially allowing a more rapid response to emerging flu strains and shortages resulting from production problems or unexpectedly severe epidemics.

Regulators around the world including the European Medicines Agency (EMEA) and US Food and Drug Administration (FDA), have thrown their weight behind the development of alternative flu vaccine processes in the wake of supply problems in the US during the 2004/5 flu season. These were caused by manufacturing problems at a plant operated by Chiron, now part of Novartis, which threatened approximately half of the US's total flu vaccine supply.

The manufacturing approach could slash the time it takes to make batches of vaccine from months to weeks, and also increase the range of flu virus strains that can be grown and incorporated into vaccines, according to Novartis.

Dr Jörg Reinhardt, CEO of Novartis Vaccines and Diagnostics said that Optaflu is: "the first major innovation in influenza vaccine manufacturing in more than 50 years." And in addition to making the production of seasonal flu vaccines more efficient, the mammalian cell technology also "offers the potential for quick scale-up of manufacturing in the event of an influenza pandemic."

CHMP approval means that the new vaccine could get a green light for marketing across the EU in as little as two to three months. A filing in the US should take place next year.

Other advantages of cell-based production is that it is independent of the availability of eggs, and the vaccines produced do not run the risk of being contaminated with egg proteins, which can cause allergic reactions in some people. Also, additives, such as antibiotics, are avoided in the Optaflu production process, said Novartis.

Virus cultivation using Novartis cell line could also make to possible to create vaccines that more closely match the original "wild-type" virus, as viruses grown in eggs often have to adapt in order to replicate.

"As a result, the antigen included in the vaccine may express more authentically the surface of the wild type virus, potentially translating into a better immunogenic and effective response," according to Novartis.

Clinical trials of the vaccine involving around 3,400 people have revealed it to be as effective as standard egg-made vaccines in stimulating an immune response against flu, with comparable safety and tolerability data.

Last year, Novartis' major rival in the flu vaccine market, Sanofi Pasteur, started Phase I trials of its own cell-based flu vaccine in the US, which is made using the PER.C6 cell line developed by Dutch company Crucell.

Other research groups have been looking into replacing egg-based production with systems based on insect and plant cells.