Monday 19 August 2013

H7N9 vaccine update...[UPDATED]

Hat tip to Dr. Nicholas Kelly for JAMA link reminder.

Earlier in the month, Zou Yong, quality directer of China based Sinovac Biotech Ltd  the Chinese Center for Disease Control and Prevention, noted that preliminary work on an adjuvanted (see bwlow) H7N9 vaccines was complete and are ready for safety  stability and clinical trials. It has already completed been through animal testing and the vaccine seems to work in our furry little friends.

In July, Novavax commenced Phase I clinical trials in adults of its adjuvanted virus-like particle (VLP) H7N9 vaccine. This trial assesses vaccine safety and immunogenicity (ability to make the recipient mount a useful immune response to the virus - A/Anhui/1/2013 (H7N9))

Helen Branswell (listed as one of Wired's best sources of infectious diseases info), writing at the Vancouver Sun, notes that 4 companies, have or will be conducting trials on H7N9 vaccines - all up costing the guy footing the bill, the US government, $1oo-million. Sanofi Pasteur, Novartis and MedImmune (using live, weakened ["attentuated"] H7N9 virus) also have products in near clicnial trial stages while GSK, CSL, Protein Sciences and Vaccinate are catching up.

As I've written before, H7N9 is a stealth virus in humans as well as chickens. In the latter instance - stealth refers to producing little disease in chickens while in the former, stealthiness is to do with problems in creating a vaccine based on H7N9 that will trigger a suitably effective immune response to what is a relatively weak trigger of human immunity.

But Branswell notes, there remains the need to define the best adjuvant (a vaccine additive "booster" that allows the manufacturer to use the minimum amount of antigen [the virus bit] while still obtaining the best immune reaction to it) however Sinovac has shown that with one, the vaccine works better than was previously expected. Its not unexpected that avian influenza viruses to need help to trigger a good immune response for a human host according to Dr. John Treanor's comments in the article.

The impact of using an adjuvant is known as "antigen sparing". The makers would like to spread the viral antigen out as far as possible to make the greatest number of doses from what they have, as quickly as possible so adjuvants are very important...and a science unto themselves.

So, a lot of work for H7N9. As Osterholm, Ballering and Kelley wrote back in May, for any pandemic vaccine to be of benefit, development time needs to be small while production scale and distribution capacity need to be big. And don't forget, the companies with the big vaccine production capacity still make our seasonal influenza vaccines too - and its no mean feat to switch off production of one product and switch on another. New vaccine technologies are required, and are being developed. Once a vaccine platform has had a successful clicnial trail path, it should be easier to leverage that as the basis for similar vaccines protecting from different viruses/viral strains, in the future.

For influenza A(H1N1)pdm09 virus, a vaccine arrived nearly 2-months after the season wave of infections had crested. Thankfully  H7N9 has not managed the adaptations required for rapid and efficient human-to-human spread.

While a licensed, killed influenza A(H5N1) virus vaccine was prepared some time back, I'm not sure about their current capacity to scale up (shelf lives being what they are)  if H5N1 is the influenza to jump to pandemic status rather than H7N9. If either do.

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