Friday, 15 May 2015

The Measles Vaccine - With Extra Life Saving Bonus


Or - why science is amazing and wonderful and cool.


Two things happened this week which reminded me just how fascinating science, and especially biology, (sorry Prof. Brian Cox) can be.

Firstly I gave a tour of our lab to some non scientists. I had 45 minutes to fill and it was a little daunting. Our lab is very specialised and technical, I didn't want to either bore them with incomprehensible science-speak or come across as some patronizing smart-arse. I think I pulled it off, and most of them seemed genuinely interested and amazed by our equipment and what we can do with it. I sometimes take it for granted that I'm involved in complex, novel research every day. So every now and then it's nice to be reminded that this isn't ordinary stuff to most people. Chatting to a colleague about it afterwards we both realised that - yeah, this is a pretty cool job, we can do stuff and find out things that would have been impossible just a few years ago and we're very privileged indeed to do that every working day.

The other thing I got chance to do was catch up on some reading. I worte some posts about Measles and measles vaccination a while ago but I'm by no means an expert on this subject and since then I've learned some new stuff. This is sort of a good news / bad news thing:

The Bad News:

I hadn't realised that getting through a case of the measles, as I did when I was five, didn't mean you were in the clear. There is a (thankfully rare) condition called subacute sclerosing panencephalitis (SSP) which can occur years after the initial disease seems to have gone away and which is sadly usually fatal. As I said, it's rare,  perhaps around 1 in 10,000 measles cases will go on to become SSP although the exact number is unclear and there is no specific diagnostic test for SSP, so it's quite possible that, since it could be 15 years since an SSP patient had the measles, the link might not be made. The good news here is that SSP is now very very rare indeed because vaccination means there are so few cases of measles in the first place (There is even an early episode of medical drama House where SSP turns out to be the mystery disease). But that isn't actually the main good news....

The Good News:

A new study suggests that the measles virus, as well as being potentially deadly and making you feel pretty damn miserable, also does a sort of factory reset on your immune system. By the time it's done you have good immunity to the measles but all your immunity to everything else is gone. All those immune cells that remember other, previous battles, against other diseases are wiped out. This means a fairly robust school child suddenly goes back to having the immunity of a vulnerable new born and in some cases it can take up to five years for them to get back to their pre-measles state. The study authors suggest that pre- vaccination, half of all deaths from childhood diseases were caused, indirectly, by measles.

Errr - how is this good news?

It is honestly  - hang on in there...
The reason we know this, is because it hardly ever happens anymore. Whenever measles vaccinations were introduced to a country the number of deaths from measles plummeted, but so did deaths from every other infectious disease too. Vaccinate against measles and you don't get measles which also means you don't get that factory reset of the rest of your immune system.

My immediate question was - how do we know it was the vaccine preventing the other deaths? Could it just be a coincidence? perhaps the vaccine was introduced at the same time as better food or sanitation? The correlation v causation question is always worth asking but in this case it really does seem to be the vaccine doing the job. The same dramatic fall in deaths is seen repeatedly in different decades and countries. Measles vaccination wasn't introduced to Denmark until 1987 but the same thing happened there, a rich, developed country. In fact the reduction in non-measles deaths is even more prominent in wealthy countries where most kids will survive measles and so go on to that susceptible period afterwards. Sadly in poorer countries many children never make it past the initial disease. Measles still kills 140,000 people a year.


This study also provides yet more evidence against some common anti-vaccination claims. Firstly there is the idea that catching a disease gives better immunity than vaccination. There is no evidence for this anyway but now we also know that catching the measles, rather than being vaccinated, actually wrecks immunity against everything else too.

I've also heard people claim that breast fed babies don't really need immunizations because they get all the immunity they need from their Mum. Breast milk does provide some immune protection although it seems to be fairly short term. But even if nature were as magical as some claim - one dose of natural measles virus and all that would be wiped out.

Biology is fascinated, there is always something new and unexpected, even when you have been studying and working with it for decades. Measles vaccination can now be considered one of the best and most cost effective health interventions on the planet. It's saved countless young lives and prevented a huge amount of suffering. But humans are pretty amazing too - we might not have realised how good it would be at the time but we made that vaccine and every scientist who worked on it, every health worker who delivers it and every parent who brings their child along has played a part in saving countless young lives.

I spend a lot of time on this blog saying "the press have hyped it up" or "the results don't really mean much" but we should celebrate our triumphs too. There is a lot of good news in science, a lot of genuine progress is being made. I wish more people could share in the complexity, beauty and wonder of it.


SBx

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