Sunday, September 18, 2005

I am gratified to learn that Bush has aparently been woken up at least a bit. A $100 million contract to purchase vaccine is a good start, with a target of a 20 million dose stockpile. I'm wondering when the completion date for that stockpile is. I'm also wondering just how much good a 20 million dose stockpile of a vaccine that requires two doses for full protection will do in a nation of 275 million people.

First of all you need two doses because the entire world population is immunologically naive. That means we have no resistance to the disease because our immune systems have never fought it, or anything like it, ever before. If you get this year's flu your body has seen similar flus before so it isn't a big deal. In 1918 a really nasty version came out that was nicknamed the Spanish flu because Spain was the only nation in the western world that hadn't buried their mass media's head in the sand due to WWI, but that's another story. It was pretty nasty but it killed well under 10% of the people it infected versus H5N1's avarage of about 50%. Why the difference? The 1918 flu started in rural Kansas from a human virus that had traded genes with some other animal virus. Becuase of that we had a fair degree of immunity to it. When it hit indigenous populations that didn't have immunity to the common flu, the death rates were similar to H5N1.

This weak immune response may be partially to blame for the fact that most victims who are tested for H5N1 initially test negative, only after the disease progresses greatly has their immune sytem produced enough antibodies to test positive. If a second test isn't done, the case is officially considered a negative. For example in Indonesia a government official's daughter got sick, aparently with no known contact with poultry since they all lived in a wealthy suburb. Then about a week later her sister gets sick, and a week after that their father gets sick. All three die. Only the father tests positive. Only the father is considered an official H5N1 death. A rational explaination would be that the first daughter passed it to her sister, and either she passed it to her father or her sister passed it to their father, thus indicating they are all victims of H5N1, and that at the very least it infected one and possibly two people after the first. Most likely the first daughter caught it from another person since there are no poultry around for her to catch it from. But since only the father is a confirmed case officially there is no human-to-human transmission, and the official suggestion is that he probably ate contaminated chicken somewhere. This case is not unique. It is the pattern found in most family clusters even when contact with poultry is present. One family member gets it, then some time later another does, and then another. This suggests that the people are catching it from each other, not all catching it from the poultry. But officially this is not considered human to human transmission and the World Health Organization classifies the disease at stage 3 on the 6 stage trip to becomming a pandemic. In reality it is at least stage 4. It might even be stage 5, as the case in indonesia suggests since the first daughter seemed to get it from another person raising the possibility that it is circulating in the population but only sporadically infecting people.

Back to my concern with the 20 million dose plan. My main concern is that 20 million doses doesn't force the creation of a great deal of new production capacity. We cannot stop production of the seasonal vaccine until the pandemic strikes. This is simple reality based on the need to continue protecting our citizens from the seasonal flu that kills 36,000 Americans each year even with modern vaccination programs that usually reach about half of the people who should be taking the vaccine. If we stop normal vaccination we can expect at least 70,000 deaths. Not a good idea. Yet when the pandemic strikes, if it is not controlled by quarantines it could kill thousands each month until the vaccine is produced. 20 million doses would be able to do two things: protect medical and emergency officials and give some hope to those closest to an outbreak.

If a single dose could provide full immunity, the vaccine could be used to stop the disease or at least slow it greatly. By vaccinating the population in an area of an outbreak, we could deny the disease a population to spread in. With two doses needed, the vaccine probably would not be able to stop an outbreak because it doesn't provide full immunity. If a person gets H5N1 after being vaccinated once they will still get sick but will probably survive, but the disease would still be able to pass on to others. So ultimately until the entire population receives at least one dose we will have a major crisis on our hands. Once that has been done only the most vulnerable would be at grave risk of death, and an outbreak could be contained by giving a second dose to those in the vicinity.

I believe that we need to create enough production capacity to provide at least 275 million doses, and to do so as quickly as possible, to allow time to produce additional doses to double up the dosing for medical and emergency personnel, and people close to an outbreak. This would do two things. First it would create a stockpile large enough to vaccinate everyone once, thus allowing control of an outbreak with a second dose from even a small additonal stockpile. Second it would force the creation of a great deal of excess production capacity. This is important because it is entirely possible that H5N1 will change between now and the time it becomes a pandemic. Having that extra production capacity would mean that a new vaccine could be produced quickly if the need arose. At present it would take 6 months to produce a new vaccine. Antiviral drugs are only partialy effective against the disease, and even then only if used soon after infection. This means that thousands would be dying every month--perhaps even thousands every week--while we wait for a vaccine. Even if it does change, it is likely that a dose of the vaccine would still be useful. Even if it only helped lessen the enormous disadvantage our immune systems face it would help.

1 Comments:

At 7:35 PM, Anonymous Anonymous said...

I'M A HEALTH CARE PROVIDE. I'VE BEEN READING EVERYTHING THAT I CAN FIND ON AVIAN FLU BECAUSE I FEAR THAT THE HOSPITAL THAT I WORK AT WILL NOT BE PERPARE. EVERYONE OF YOUR ENTERIES SHEDS LIGHT ON THE LIMITED INFORMATION THE PUBLIC IS RECIEVING ON THE NEWS. I FEEL THAT EVERYONE SHOULD PERPARE EARLY. LOOK AT IT THIS WAY, YOU NEED THE ITEMS ANYWAY, SO YOU WON'T HAVE TO GO SHOPPING FOR A WHILE. ALSO THEIR WON'T BE ANY N95 MASK ONCE IT STARTS, THE WORLD WILL BE ON BACK ORDER. KEEP POSTING. I WAS CONCERNED WHEN I SAW 0 COMMENTS ON EACH ENTRY. ARE THEY SPEECHLESS OR JUST NOT AWARE.

 

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