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Internet Source: ABC News, Radio National Transcripts, August 28, 1995
Source URL: http://www.abc.net.au/rn/talks/8.30/helthrpt/hstories/hr280803.htm


Radio National Transcripts:
The Health Report
Monday, 28th August 1995 Some surprising benefits from measles immunisation that have nothing to do with measles protection

Dr Norman Swan: And some good news on the immunisation front: measles immunisation, at least in developing countries, seems to have a beneficial effect beyond its protection against measles. Dr Peter Aaby, a Danish epidemiologist who has been working in Africa for the last 17 years, has reviewed all the published studies of the impact of measles immunisation on survival. He spoke to me from his office in Guinea-Bissau.

Peter Aaby: It has been known, probably for the last ten years, that measles immunisation had a very marked impact on survival for kids in developing countries, and that the immunisation reduced mortality more than you could expect was due to the acute measles infection. So it has been assumed that measles infection probably had long term negative consequences and that the immunisation also prevented these long term consequences that act like a chronic state of measles infection. That was what had been assumed. What I've done now is re-analysed those assumptions and re-analysed a number of these studies.

Norman Swan: Children who have been immunised against measles have up to a 50% lower chance of dying in childhood compared to those who haven't been immunised. It's a huge benefit, which is far larger than you'd expect if all it was doing was protecting against the measles virus alone.

Peter Aaby: And I found the same pattern say in Bissau and Senegal and Burundi and in Bangladesh. So measles vaccine obviously prevents you from dying from measles. But that's not really what the impact of the vaccine is. It's much more an impact on other things, particularly diarrhoea. We are finding a very marked reduction in diarrhoea mortality from having received measles vaccine. This was an effect which was particular for the girls, and that's another interesting aspect here, that the impact of the immunisation seems to be particularly marked for the girls.

Norman Swan: Is there any explanation for the sex differences in the effects of the immunisation?

Peter Aaby: I don't think we have any good explanation at the moment - apart from the fact that the standard vaccine is particularly good for girls. I think there are so many things which haven't really been studied. And I have observed that it's more severe to be infected by the opposite sex. So obviously, sex is much more important I think in this viral infection than has been noticed before.

Norman Swan: And do you find the same reduction in mortality for a child who's survived the measles infection? Does it seem to be measles immunity that produces the effect?

Peter Aaby: I think it's some form of immune stimulation is the effect. Both the measles infection and the measles immunisation stimulate like interferon, which could be reducing other things. And we have found a boost of T-cell levels after measles infection. But probably you are getting a general stimulation of the immune system. Most Western medicine has been looking at these diseases as, measles is just one particular disease, you prevent it and that's the end of the story.

But it seems to be a much more general impact on the immune system, and that's preventing other things from happening. And that's particularly important in an environment where you are exposed to a whole lot of other infections. If you have boosted your immune system then that's probably preventive. And you find the same thing after the infection, and the same thing after the immunisation.

Norman Swan: And presumably the fact that it happens after the infection as well as after the immunisation, excludes the possibility that children who have had the immunisation are somehow different, perhaps slightly better off, slightly better nourished, in the community?

Peter Aaby: Yuh. This is not just a selection bias.

Norman Swan: What's the impact of diphtheria, tetanus, pertussal or polio vaccinations?

Peter Aaby: You do not find the same thing for kids who have received the pertussis vaccine or the TTP and the polio vaccines. There's no difference in mortality.

Norman Swan: Dr Peter Aaby. And if you're confused about the situation with the measles infection, it was only the children who'd survived the measles infection who in fact did better in the long run. His paper was published in the British Medical Journal.

This is a transcript of the Health Report as originally broadcast on Radio National, the Australian Broadcasting Corporation's national radio network of ideas.