Friday, June 12, 2009

H1N1 - How do we know vaccines are effective and safe?

There's been a lot of talk recently about vaccines especially since we have gone 'pandemic' and begun moving into the mitigation zone. See Wall Street Journal article.

Vaccines are made by producing either live 'bugs' which have been attenuated so that they don't produce disease, or by engineering a protein that carries all the required antigens and that will be able to 'teach' the human body to immunologically recognize the bug and therefore to produce an immunological defense against it. These are usually industrially complex processes many of which are proprietarily protected and unique to each manufacturer. This generally makes it difficult for the regulators like the FDA and our own Health Science Authority (HSA) to figure out which processes are safe and acceptable etc. The final vaccine is analyzed principally as a chemical product to ensure it does not contain known pathogens, and biological contaminants and toxins.

Preclinical or animal testing for safety and effecacy is kinda useless although it is often done as part of the vaccine development process. Vaccine efficacy and toxicity is highly species specific because it engages the immune system, and in this case animal indicators of efficacy and toxicity are almost totally unrepresentative of whatever may happen in humans. At best, it picks up only very gross and obvious effects.

There is a mandatory period of clinical testing. But again, this is often very artificial because at best it only demonstrates the ability of the vaccine to induce an immunological response. This antibody response does not mean there is immunity against the bug in a real infection since this clinical testing is in normal uninfected individuals, and the anitbody produced tested against a test tube bug. So real efficacy against the bug can only be presumed. One can really only know the true efficacy when the vaccine is trialed in the context of the prevention of a real infection/epidemic. This is difficult to do and takes a lot of time because the occurence of an epidemic is unpredictable.

So most vaccines are licensed into the market, based on very indirect evidence of efficacy and safety. To makes matters even more uncertain, many postulated toxicity effects of vaccines appear very late after the vaccination. For a new vaccine, such delayed toxicity may never ever be discovered until many many years down the road. Many toxic effects will in fact never ever be detected or proven.

All this makes the licensing of vaccines very difficult. Even for large regulators such as the FDA. You can read more about this here. (FDA’s Role in the Regulation of Vaccines ). Our HSA doesn't even tell us how this is done. Vaccination programmes unlike most other drug treatments are given prophylactically to normal healthy people, on only the anticipation of a possible infection. In this context, our expectation of safety should be even more critical. But in fact, for vaccines, our knowledge of the efficacy/toxicity balance is even more clouded.

So how does our HSA do it? Even more clouded.

When an emergency situation arises, such as the occurence of a pandemic, there can be a suspension of regulatory restrictions. In the US, :
"An additional tool available to speed product availability is the ability for FDA to allow the use of unapproved products and unapproved uses (so-called “off-label” uses) of approved products, in a declared emergency, under the Emergency Use Authorization (EUA) provision of the Food, Drug, and Cosmetic Act. This authority was expanded under the Project BioShield Act. To authorize such emergency use, FDA would need to find that the agent can cause a serious or life-threatening disease or condition; that based on the available information it is reasonable to believe that the product may be effective against the disease or condition; that the known and potential benefits of the product’s use outweigh the known and potential risks; and that there is no adequate, approved and available alternative. "

We don't know if such an 'emergency use authorization' exists in the Singapore context, and under what conditions it make be activated. For the current H1N1, there seems no justification since for it (yet) since there does not seem to be any evidence that it can be considered to 'cause a serious or life threatening disease/condition'.

So HSA/MOH, can provide us some assurance that should we try and move into mass vaccination programmes for H1N1, that the vaccines being rushed into production (especially by our A*star/EDB boutique biotech companies), are safe and effective?


Anonymous said...

may be the actual virus is safer....:)

gigamole said...

yeah.... :)

but cost benefits are really difficult to assess in situations like these. On one hand, there is the immediate 'feel protected', 'I have done something about it ' factor, and on the other, the possibility of delayed toxicity (say autism or some debillitating neuopathic degeneration) which nobody may be able to prove and which will become somebody else's public health problem.

What would you do if you were a public health officer making the decision?

auntielucia said...

I'm not sure I want to be vaccinated with a vaccine that's just been rushed to market.

However, I wonder whether we do enough in S'pore to detect and protect? Esp at the airport. Are the part-time fresh hires manning the scanners up to their job? How come so many are getting thru becos they have no fever and then develop the H1N1 thingie thereafter?

gigamole said...

The problem with H1N1 is that the incubation period is a couple days, so the first few days, of infection is symptom free. By the time fever etc appears and detectable by thermal scanner, patient already infected for a couple days and have potential spread.