Thursday, September 17, 2009

H1N1 vaccine - areas of concern

So the MOH has clarified that the vaccine will be offered pretty much at cost and for about the same price as the seasonal flu vaccine. Channelnewsasia reported price range of $22-38. Which is somewhat more than my earlier 'rojak' estimate of $10 per shot. But it's still affordable.

What MOH needs to clarify though is whether the GSK vaccine requires the squalene based AS03 adjuvant. The safety of the AS03 adjuvant, like the Novartis MF59, has been in question for some time. These adjuvants serve the purpose of heightening the immune response, resulting in the necessity of using a smaller amount of antigen. It was deemed necessary only because anitigens were difficult to produce in large quantities. The problem is that, theoretically the immune stimulation may induce the body to react against its own tissues. One of the suspected consequences has been the development of the Guillain Barre syndrome. This is a rare possible adverse event associated with the use of these vaccines. Whether this is a real consequence or not is hard to determine as these tend to develop over years after the vaccination event, and hence the causal link is hard to establish.

The US FDA has not yet licensed the use of these adjuvants, although it seems to preparing for their use should an H1N1 emergency arise. It has also not yet authorized the emergency use of these adjuvants.

Recent studies have shown that single doses of the un-adjuvanted vaccines are adequate to produce the antibody levels required for protection. So theoretically, we should not need the adjuvants.

Although the risk of Guillain Barre syndrome, even if real, is very low. It is nevertheless necessary to consider the risk when exposing children to vaccines containing these adjuvants. We need to appropriately balance the benefit of protection against a potentially fatal HiN1 infection, and the potential risk for a vaccine-adjuvant related auto-antibody response.

Parents do need to be aware. The MOH should also be mindful of parent's concerns and be transparent about whether such vaccines contain the squalene adjuvants. Patients do have a choice, and should be empowered to make a decision about the risks they are prepared to take.

There is a fairly decent review here:

A related question, and something that I have found difficulty in getting information about is, how the HSA regulates something like this? Does it have a policy about squalene adjuvants? How does it regulate such novel vaccines in a 'not sure if there is a pandemic' situation?

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