How Much Protection Immunization Gives


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Posted by shareebee on Thursday, 11. August 2005 at 12:35 Bali Time:

In Reply to: What's the treatment for WC? posted by majik on Wednesday, 10. August 2005 at 14:37 Bali Time:

This is a copy and paste from http://www.whoopingcough.net/

Immunization gives a certain amount of protection to an individual but a great deal more to the population as a whole. And whether somebody who has been immunized gets whooping cough or not depends on a great many other factors as well. Vaccine manufacturers tend to quote protection levels of about 80%.

Most people are surprised when an immunized individual gets it. But it should not cause surprise. It is a complex organism which needs to be attacked in several different ways at once to stop it infecting. The natural infection provides these ways for the future, but vaccine is a poor substitute for the real thing and it is only able to do a poor imitation of natural infection. Whether you get it or not depends primarily on whether you come into contact with it. If everybody else has been immunized then the bug never gets much of a chance to spread itself around, so you may never come into contact with it. If nobody is immunized then it will always be around and you will come into contact with it so often that even if you have been immunized you will get it sooner or later when your resistance is lowered by having a cold or something similar.

Nobody has been able to measure the effectiveness of the vaccine precisely because it depends on the ability of the bug to spread itself around. This will depend to an extent on how many people have natural immunity and how many have vaccine immunity which is not so good. The number of people with natural immunity is probably getting less as the pre-immunization generation gets older, but some of the immunized ones will perhaps get an unnoticed boost from natural infection if it comes back a bit. So it is all complex, and there is no good way of measuring susceptibility by measuring antibodies as it is also so complex.

What we do know is that when a population of children gets immunized the number of cases falls dramatically, and it is enough to ask of a vaccine that it should do that. It is also generally agreed that individual protection falls quite rapidly after the last shot, so that 5 years later the amount of protection may have fallen to quite a low level.

The main purpose of immunization is to stop young babies getting it because they can die. So as long as their older brothers and sisters are protected by immunization they are relatively safe. But because adults are not getting their faded immunity boosted by natural infection, some of them are getting it and passing it to their children! Nobody has worked out the best way of keeping adult's immunity high yet. We are probably going to have to wait for better vaccines to come along to solve that one.



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