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Pandemic flu vaccine yields worse than expected.

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All Nature’s pandemic flu coverage is collected on our news special page.

Efforts to produce vaccine against the pandemic H1N1 2009 virus have run into problems. Vaccine makers have told the WHO that the ‘seed strains’ grown to produce vaccine against the pandemic virus are giving poor yields of antigen. The yield is a quarter to a half of that vaccine makers typically get for seasonal flu vaccine production. WHO has now started to try to make a new set of seed strains using new viral isolates – a process which will take around a month – in the hope that some perform better. But if improved yields aren’t forthcoming, the amount of pandemic vaccine available from existing production plant capacity could be cut by half or more, whereas there already isn’t enough to go round.https://www.nature.com/news/2009/090512/full/459144a.html


First a quick recap on what a seed strain is. Vaccine is grown up, usually in hen’s eggs, using seed strains – these are hybrid viruses, designed to have the surface proteins of the virus against which a vaccine is needed, but the internal proteins of a faster growing and higher yielding flu strain. There are two ways of producing such a hybrid. One is by reassorting the target virus with the high yield strain – for a wonderful account of this process by Doris Bucher, a microbiologist at New York Medical College, see this Nature news Q&A; the other is by using reverse genetics. The virus itself seems to be growing well, but it’s not producing enough of the key haemagglutinin antigen component of the vaccine – see also. It just seems to lose the antigen, perhaps because it is unstable. “We have little idea of what makes a good yielder,” says Marie-Paule Kieny, WHO’ vaccine research director.

The WHO’s flu labs have produced 5 seed strains against the pandemic 2009 virus, two by reassortment, and three by the more modern process of reverse genetics. Out of the five, the best yield came from NYMC X-179A, a traditional reassorted seed strain grown in Bucher’s lab, which used the target pandemic isolate A/California/07/2009 – but even it’s yield was half what one usually gets against seasonal flu vaccine, with the other contenders’ yields being as low as 25%.

Bucher is now making a new seed strain using a new isolate, A/New York/18/2009, and other WHO labs are doing likewise using the New York and other isolates. There’s a possibility these efforts might give a better result: in the past, a seed strain against H5N1 using a 2004 isolate from Vietnam also gave poor vaccine yields, but later ones using isolates from Indonesia and elsewhere gave good yields.

Although the process of making new seed strains will take about a month, it shouldn’t hold up the vaccine production timeline overall, because clinical trials can get underway using the first batches of vaccine now coming online from the poor yielding strains, says Kieny. Regulatory authorities say no new trials would be needed, she adds, for a higher yielding strain should one be generated and be switched over for use in large-scale vaccine production.

For my more detailed and analytical recent coverage of pandemic vaccine issues, see:

US ramps up swine flu protection

Vaccine decisions loom for new flu strain

Q&A with Doris Bucher, a microbiologist at New York Medical College, who is renowned for her green thumb in engineering viruses that yield high amounts of flu vaccine.

Q&A with Marie-Paule Kieny, vaccine research director of the World Health Organization

Comments

  1. Report this comment

    Uncle Al said:

    WHO cannot diddle a swine flu vaccine? 1) “massively parallel” to find a good starter culture, 2) Only hire lab chiggers that Personnel despises and fears – obsessive compulsive competence, and 3) unemploy 90% of all managers on the project – nobody needs REMFs.

  2. Report this comment

    Dr. Richard Welser said:

    Well, you can bet that since Baxter included the live H5N1 flu virus along with their vaccines for the regular flu H1N1 a few months ago …. I will not be taking any flu vaccine this year or any subsequent year.

    I’ll gladly take my chances with the flu. And WHO can go to that very hot place with my blessings. Along with any police forces mandated to arrest me – when – I refuse.

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