My regular coursework is going on side-by-side with the project. And we’ve had guest lectures this week by a professor from the National Institute of Immunology, Delhi. A few of us were talking to her after class, and she told us that there was such a thing as too much vaccination.
When a bug infects you and you’re able to fight it off, your body keeps some immune cells in your body which are capable of identifying the bug, should it ever infect you again. That way, your immune system will know that there’s been an infection, and it will also know what caused the infection. It will be able to tackle the infection that much more quickly. That’s why you never get the chicken pox more than once in your life.
When the second infection occurs, the cells that “remember” the infection (called memory cells) have to multiply and change into cells that can actually tackle the bug. But there’s a catch. Cells in your body can multiply only a certain number of times before they stop. (Incidentally, that limit is one of the reasons cells don’t turn cancerous very easily) So, if you have repeated infections, your memory cells will hit the limit and once they die, they won’t be replaced.
Now, vaccination is like giving you a mild infection that you can recover from, but which will also equip you with memory cells. That way, the body responds much quicker when an actual infection takes place.
Repeated vaccination is like repeated infection. There’s a risk that you could lose your immunity against a bug if you get too many booster shots too often. Which apparently is what is happening with the oral polio programme. In Delhi, oral polio vaccine campaigns are conducted nearly every month. Children under 5 are given oral polio drops. Which means if a child has very conscientious parents, it could get up to 60 doses in 5 years. That’s more than the limit on multiplication of cells. And that potentially defeats the whole purpose of the programme. There isn’t any experimental evidence yet to show that children who’ve gone through such a regimen have impaired immunity against polio, but there’s a risk that it could happen.
So, here’s the take home advice. If anyone tells you that you need booster vaccinations for the most common bugs more often than once in 6 months, check again somewhere else. Otherwise it might be as good as not getting a shot at all.
3 comments:
am not sure, but i think the pulse polio program says that the child is supposed to go for every alternate dose. that'd bring it up to around 30 doses in 5 years. as bad?
(am asking because that's the system my sister followed with my niece)
oh, but what happens if I get the chicken pox(for example) once and then I come in contact with people infected with chicken pox on a regular basis? (suppose I'm a doctor) Won't that mean that my body fights off the chicken pox virus many many times without me knowing about it?? Does that have an upper limit as well?
Pseudo, I still don't think its a very good idea. 30 is still quite a lot. The old twice-a-year programme, with doses only in Dec and Jan probably makes more sense.
Chitra, it's not just a question of exposure, but also about how many viruses you're exposed to at once. So a doctor who's already had the disease should be safe unless his patient spits on him or something like that!
There's one other thing I didn't mention here. If attacks happen pretty often (if the disease is endemic), there's a chance that the body can produce new memory cells ab initio. But a booster dose doesn't generate the kind of pathogen load that ensures new memory cells will be produced.
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