Yes or no? Why do (don’t) we take the flu jag?
It’s flu jag time again. We’ve known about vaccination for a very long time. We’ve all heard of our man, Edward Jenner. In 1796 Jenner inoculated eight year old James Phipps, the son of his gardener, with pus from the blisters on the hands of a local milkmaid. The milkmaid had caught cowpox, a less extreme disease, and the boy became immune to smallpox.
In case you’ve got a pub quiz coming up, the hide of the cow that gave the cowpox to the milkmaid (are you following me?) now hangs in the library of the medical school in St George’s Hospital in London – there’s fame for you!
In fact vaccination against smallpox, an infection that used to kill about a fifth of sufferers, had been developed hundreds of years before in India and China. In a technique known as variolation, dried smallpox scabs were blown up the nose and causing a milder form of the disease – in other words, your chance of dying was only 1-2% rather than 20%.
Lady Montagu was the wife of the English ambassador to Turkey, and she had been badly infected and scarred by smallpox herself as a girl. She learned about variolation and in 1717 had her son inoculated against smallpox (having tried it out on a few prisoners first) and persuaded the rest of her family to get it done too when she came back to London. Smallpox was declared extinct in 1979, although I’m old enough to remember giving one of my patients a smallpox vaccination in my first year on the job.
Polio is tantalisingly close to going the same way, saved for the time being by humans arguing with each other. Bill Gates gives billions of dollars to vaccination campaigns in poor countries. Virtually everybody agrees that immunisation is a Good Thing – for other people anyway, especially other people in developing countries. Flu immunisation is not a new thing either. It’s been around since the American Army started using it in 1945.
The question I want to think about this week is why we agree, or refuse, to have our winter influenza shot – the flu jag. What are the pros and cons? And how good are we at weighing up the risks? (I’ll give you the answer now: not very good). What risk is there you will catch influenza?
5-10% of the population will catch flu in a normal year, rising to 20% in epidemic years, the last one of which was 1989/90 in the uk. So, on average, you will get flu once in every twenty years. How unpleasant or dangerous would that be? Anybody who has had ‘real’ flu will tell you it’s pretty miserable. More than pretty miserable. “The worst illness I’ve ever had,” and “If there was a £50 note on the floor by the bed, I wouldn’t be able to pick it up” are common remarks from fit young people afterwards.
As to how dangerous it is, we can’t put an exact figure on this. 12 people were recorded in Scotland as having died from influenza in 2010, 131 in 2000. This low figure is because doctors often don’t think of influenza when writing out death certificates, but tend to use diseases like ‘pneumonia’ or ‘heart failure’ that were brought on by the flu. But last winter (a ‘good’ winter as it happens) 1420 more Scots died in the four winter months than in the four summer months. This ‘excess winter mortality’ tends to be worse when there is a lot of flu about, and it is likely that flu is responsible for lots of severe winter illness and a couple of hundred deaths in Scotland every year. Even so, an average person’s chance of dying from flu is small, around 0.004% each winter.
But how risky is it for me?
That depends. The flu virus really goes to town and licks its lips (or would if it had them) when it finds a victim who is old or worn out, particularly if the victim has got a nice rattly chest, a dicky heart or blood with loads of delicious sugar. Or a baby.
Is it as risky every year?
This is where a good head for gambling comes in handy (if you see what I mean). The odds are different every winter. We’ve had a good run in the last decade, but every few years there’s a spike in the figures.
How effective is the vaccine?
Again it’s frustratingly hard to be accurate, but the best estimate is 60% effective. It is actually works less well (50%) in older and sicker people. And because the flu virus changes its spots every year, scientists have to race against time to guess what it’s going to look like every winter. They do this by checking out the strains doing the rounds in the previous southern hemisphere winter. If they guess wrong the flu vaccine still works, but not as well.
A common reason for not taking the flu jag is that you, or a friend, took it one year and got a bad cold a week or two later. To look into this, some researchers in Brazil followed up hospital workers who had taken the flu vaccine very carefully. Almost all the ‘flu’ they got later that winter was caused by other viruses.
What are the side effects?
About one in three people who take the vaccine will get a sore arm, or a brief headache, runny nose, sore muscles or tiredness.
And how dangerous is the vaccine?
Very not dangerous. The worst problem could be a one in a million chance of getting muscle weakness called Guillain-Barre syndrome. And there is a lot of argument about whether this really happens or not.
So how good are you at weighing up all these figures and working out whether you should take the flu immunisation?
Let’s go back to smallpox and put ourselves in the shoes of Lady Montagu. She had to weigh up the risks for her son three hundred years ago. The disease was common in Turkey and London, causing one in ten of all deaths at the time. She had had smallpox herself, had survived but bore the scars on her face. She learned about a technique that had been used for hundreds of years in a foreign country she admired. There were no huge vaccine trials to read, but she decided to let a doctor deliberately infect her son with smallpox – and it worked.
We all have to make the same calculations and our skill at working out this risk is called our ‘risk intelligence’. Like all forms of intelligence, some people are much better at this than others. Some of us have the make-up of daredevils, some of us are ‘risk averse’. As you can see, the figures are pretty complicated and many of us leave it to the experts. That’s what I do, and I’ve had the flu jag for 30 years.
There’s still plenty left in the surgery and now’s the time to get it!