A week ago in H7N9 Vaccine Realities I wrote about the difficulties of producing, distributing, and deploying a novel flu vaccine in a timely manner, and in a quantity sufficient to heavily impact a pandemic.
Today, Helen Branswell has a report on another potential hitch in the production of an H7N9 vaccine; earlier studies indicate that H7 vaccines may require large amounts of antigen to induce a robust immune response.
First Helen’s article – which includes comments from CIDRAP Director Michael T. Osterholm. Go read her article, then when you return, I’ll have a little more.
Making an effective H7N9 vaccine may prove challenging: experts
By Helen Branswell, The Canadian Press
If the news that H7 vaccines may require 12 times more antigen than regular seasonal flu vaccines sounds vaguely familiar, it may be because we ran into this same problem in 2007 when Sanofi tested their H5N1 avian flu vaccine.
From Sanofi Vaccine Hits A Snag:
In March of 2006, an interim analysis of this vaccine published in the New England Journal of Medicine (NEJM) indicated that it required two shots, of 90 ug of antigen each, to produce an acceptable immune response in 54% of the test subjects. That is roughly 12 x's the antigen required for a standard flu shot, and considerably less effective as well.
The standard solution advocated for boosting the effectiveness of pandemic flu vaccines is the inclusion of adjuvants.
Adjuvants are (usually proprietary) chemicals that are added to vaccines to increase the recipient’s immune response, and can dramatically lower the amount of antigen needed in a vaccine.
Since they are somewhat controversial, were not used in flu vaccines in the United States during the 2009 H1N1 pandemic, but they were widely used in Europe.
At first, concerns over their use seemed unfounded, but the fall of 2010 we began to see reports of an increase in narcolepsy among children who received GSK’s Pandemrix vaccine, which included a squalene-based component called AS03, used as a adjuvant.
For early coverage of this story, you may wish to revisit Finland Suspends Use of Pandemrix Vaccine and EMA To Review Pandemrix Vaccine, both of which I wrote in August of 2010.
While the cause of the increase in narcolepsy in children remains unsolved, In February of this year the UK’s HPA published a statement ( see Pandemrix Vaccine Linked To Childhood Narcolepsy In England) that found the absolute risk of a child developing narcolepsy from the Pandemrix flu shot appeared to be about 1 in 55,000.
The authors then cautioned:
`Our findings have implications for the future licensing and use of adjuvanted pandemic vaccines’.
While no increases in narcolepsy were detected in adults who received the vaccine, promoting the idea of including an adjuvant in another pandemic vaccine – even if restricted for use in adults – may prove difficult.
Of course, should the next pandemic flu virus prove particularly deadly, any concerns over the risks of taking an adjuvanted vaccine may soften considerably.