Tamiflu (Oseltamivir ) stockpiling for use during an influenza pandemic, I assume for convenience and brevity to be H5N1, is controversial—at best. Not even the very knowledgeable among the Cyber Flu Community fully agree on the issue, but it is an issue that evolves so periodically we dust it off and reconsider it afresh.
A brief rundown of some of the operative issues that reside within the Tamiflu issue may be warranted.
- Obtaining the end product (Tamiflu) is a difficult and time consuming process.
- Tamiflu is expensive.
- Tamiflu has a finite shelf life, thus the earliest acquired (expensive) stock is already expiring, unused.
- There will never be enough for everyone who would likely benefit from receiving it.
- It produces resistant strains of influenza virus, thus it will render useless the expensive stockpiles.
- WHO Clinical Management:
Modified regimens of oseltamivir [Tamiflu] treatment, including two-fold higher dosage 1 , longer duration and possibly combination therapy with amantadine or rimantadine (in countries where A(H5N1) viruses are likely to be susceptible to adamantanes) may be considered on a case by case basis, especially in patients with pneumonia or progressive disease.
That's double the dose for up to double the standard length of time, requiring 40 capsules instead of 10, potentially slashing our stockpiles to a quarter of their standard treatment courses. A standard treatment course consists of 10 capsules, 2 a day for five days.
Some or all of the above, but by no means a full listing of all the relevant issues, have weighed on whether or not private and governmental entities stockpile Tamilfu against the future threat of an influenza pandemic.
For those interested in exploring the issues of Tamiflu from a scientific perspective I recommend EffectMeasure's latest offering on Tamiflu, which in turn will link to an entire series on modeling antiviral resistance.
Here is the opening bit to (hopefully) whet your appetite:
Posted on: November 8, 2007 7:23 AM, by revere
Via the Clinician's Biosecurity Network Report we learn of a new study from the Webster St. Jude laboratory in Memphis showing that H5N1 can mutate to oseltamivir (Tamiflu) resistance without any loss in genetic fitness. Tamiflu resistance has been seen but infrequent and there was considerable evidence that the resistant strains were handicapped in some way, thus making them either less virulent or less transmissible. The hope was this was a built-in limitation. Now we know it isn't…
And here is the piece that inspired the Revere post…
CBN Report: Drug-Resistant H5N1 Influenza Viruses May Retain Fitness
By Eric Toner, M.D., November 1, 2007
Should widespread resistance to antiviral drugs occur in a pandemic influenza strain, the chance of limiting the disease outbreak, either locally or globally, or treating the sick with antiviral medications would be greatly diminished. This has been of particular concern because many isolates of H5N1, the virus currently considered to have the greatest pandemic potential, are known to be resistant to one class of antivirals, the M2 inhibitors, and a few isolates have evidenced resistance to the only other class of influenza antivirals, the neuraminidase inhibitors (NAI). It has been posited, however, that the risk of NAI resistance becoming widespread might be relatively low because it was thought that as influenza viruses acquire NAI resistance, they become less fit and as a result, cannot be transmitted efficiently.
Continues at Clinician's Biosecurity Network.
As is usual with things relating to pandemic influenza issues aren't clearly understood, clearly defined, or easily made so, but there are people out there, in the trenches, trying to remedy that, and the Reveres at EffectMeasure are longstanding exemplars. My humble thanks for all they do in that endeavor.