Stardate 20020226.1231

(On Screen): An enormous amount of work is going on to try to develop a vaccine against HIV. It's completely understandable; HIV is a terrible disease which already is a major killer and which is expected to continue to infect people in vast numbers for the forseeable future if nothing is done. In one African nation now something like one third of all adults are HIV-positive; this is catastrophe and it's only going to get worse.

Viruses are insidious; vaccines have traditionally been the only really effective way to treat them. But when a decent vaccine can be created, the results of using it can be spectacular and many traditional viral killers have been wiped out in the industrialized world with vaccination: smallpox, polio, measles. The only time these days that those kinds of diseases recur is when parents forgo vaccination.

So it's easy to understand why everyone hopes that a vaccine for HIV will help prevent spread of the disease and deaths by AIDS. I'm not a doctor, but I'm deeply concerned about all this because everything I know about HIV suggests that a vaccine will be useless against it. I wrote about this in depth last year. I've tried a couple of times since then to get people in the field to tell me what was wrong with my logic or knowledge, but so far have not been successful in getting an answer from anyone.

Briefly: vaccines do not actually prevent infection. What a vaccine does is to make the body's immune response to infection much more rapid. As a result, the peak viral load is far lower. In essence, you get sick and get over it so rapidly that you don't even notice you were infected. But that works because for all the classic viral killers, they are only dangerous if the viral load is high.

That doesn't seem to be the case for HIV; a chronic low blood level of the virus causes cumulative damage which leads to AIDS. A vaccine won't prevent that.

The diseases that vaccines have been successful against are the ones which you could only get once. If you got smallpox or measles and it didn't kill you, you can never get it again. What a vaccine does is to fool the immune system into thinking it's had the disease, which means you can't get it "again" for the first time.

But some other kinds of viral diseases are chronic, and I'm not aware of any such which have been successfully treated with vaccination.

For example, Herpes is chronic. Once infected, you've got it for life. You don't suffer symptoms from it continuously; rather, you get periodic outbreaks. Each such outbreak is fought by your immune system and the interesting thing is that each time the immune system wins, which is why you get over the outbreak. But in the mean time, the Herpes viruses have hidden in a place that the immune system cannot go, and will eventually come out again for a rematch. This continues to happen for the rest of your life.

I don't have Herpes, but I do suffer from warts on my hands. They come and they go; I've been getting them since I was a little kid. They're caused by a family of viruses called Papilloma and they do much the same thing that Herpes does: they hide in the nerve ganglia.

A vaccine isn't magic; it doesn't prevent disease, it's just a shortcut to dealing with it the first time you are exposed. There's nothing more to it than that. But for a virus like Herpes or Papilloma, the second outbreak in a natural progression of the disease would be exactly the same as the first outbreak in an immunized individual. That's really all a vaccine does; it makes your body treat the first exposure as if it was the second. That doesn't work for Herpes or Papilloma; we keep getting outbreaks from them. So it's not clear a vaccine would be of any use.

By the same token, people who are infected with HIV have an initial battle with the disease where the blood level rises to very high levels. But the immune system fights back and beats it; it is reported to feel a bit like a case of flu (which is about right for a moderate but not massively nasty virus; most of the symptoms of flu are actually side effects of your body's immune response rather than primary effects of the disease). But then the body is sensitized to the HIV virus – but AIDS happens eventually anyway, and the person dies. There has actually already been a vigorous immune response to HIV, and it didn't help. So how would a vaccine change the long term progression of the disease? It seems to me that all it would do is to prevent that initial big pulse of viruses, and on exposure put you into that long term chronic progression which leads to AIDS and death anyway. It's possible that it might be slower due to starting with a lower initial base, but the end would be the same.

Someone help me out here. What am I missing? If a vaccine does not actually prevent infection (and it doesn't), and if any viral load of HIV will eventually kill you, then what is the point of a vaccine?