When I first opened this blog, I said it was because the space constraints of FaceBook made it difficult to discuss some matters in the detail they require. The necessity of having a Covid vaccine is one such instance.
It can be a tricky, emotive, and complicated topic, so I'll try to keep this as honest and simple as possible So the following numbers are purely illustrative. They're not be taken as accurate, pure science, but as an idea of why vaccination is important.
Firstly, let's look at a virus, any virus. There's a lot of talk about the 'R' number. That's just a measurement of how many people a person, on average, will pass the virus on to. So, if a virus has an R of 1, what does that mean? It means that. if we don't change our behaviour (social distancing, etc.), if 10,000 people have it today, then 10,000 will have it tomorrow, and 10,000 will have it in a week, and 10,000 will have it in 6 months.
Some of the original 10,000 won't have given it to anyone. Some will have given it to 3 or 4 people. But, on average, each one person will have infected one other person.
But what if it's a nasty virus and the R number is 3? That means that each of those people gives it to 3 more. So now, those 10,000 people become 30,000. That then becomes 90,000. That becomes 270,000. That becomes 810,000. That becomes 2,430,000. That becomes 7,7290,000. That becomes 21,870,000. And that becomes 65.5 million. The entire population of the UK infected from a starting point of 10,000 people, in 8 steps. Of course, it'd never come to that, but that's just to illustrate how fast things can change.
But let's say we could reduce that. Let's say the R number was reduced to 0.75. 10,000 would become 7,500. Then 5,625. Then 4,219. Then 3,164. Then 2,373. Then 1,780. Then 1,335. And then 1,001. That's what we've done with the Coronavirus with lockdown. We've not got R down to 0.75, but we've got it below 1 by closing the pubs.
So how do vaccines help? Some say that there's no point in being vaccinated against a virus if it's not 100% effective. Well, let's say vaccines reduce your chances of getting the virus by 75%. 3 people out of 4 who would have got the virus no longer do. But 1 out of 4 does. That means those 10,000 people, instead of passing it on to 30,000 people, will only pass it on to 25% of those. Which is 7,500. So the R number has come down from 3 to 0.75, because of the vaccine. So for a virus with an R of 3, if the vaccine is 75% effective, it reduces the R to 0.75. Instead of growing by x3, it's shrinking by a quarter.
But what it some people aren't vaccinated? How many people do we need to be vaccinated to control that virus? Well, we know that we need enough for the R number to fall below 1. Remember, an R of 1 means the numbers are stable, above 1 and the numbers with it are growing, below 1 and numbers are shrinking. We said that the virus has an R of 3. So 200 people give it to 600 more people. If everyone were vaccinated with a jab that's 75% effective they'd only give it to 25% of those 600, so that's 150. 200 becomes 150, that's an R of 0.75.
But let's say a quarter of those 600 weren't vaccinated. 150 would get it from not being vaccinated, and 112 (25%) of those vaccinated would get it, that's a total of 262. So 200 people pass it on to 262. So if the virus has an R of 3, and the vaccine is 75% effective, and only 75% of people get jabbed, the R remains above 1. And if we don't want the virus to spread, we need to keep the pubs shut.
Let's try some more sums. If 90% are vaccinated, 60 of the 600 would get it because they weren't vaccinated, and 135 who were vaccinated would get it.
60 + 135 = 195. 200 people pass it on to 195. The R has just dipped below 1.
So we would need 90% of people to be vaccinated to bring the R below 1. Or alternately, keep some lockdown measures in place.
So that's a theoretical virus. What about the Coronavirus?
It's very difficult to say with any degree of accuracy where we are with Covid, because we're nor completely sure of the virus's true R number, nor exactly how more infectious the new variants make it, nor exactly how much the vaccines prevent spread.
But we do know that the virus has an R above 1 (a long way above 1). And we do know the variants increase this. And we do know vaccines reduce your chances of passing it on.
And we also know that we've only been able to bring the R down to below 1 with some pretty hefty changes to our lives.
And we do know:
- The R number needs to be below 1
- This virus has a natural, unchecked R of way over 1
- There are only 2 ways to bring the R number down (a) lockdown measures, and (b) vaccination
- The more people who are vaccinated, the fewer lockdown measures are needed.
- The fewer people vaccinated, the greater the number of lockdown measures must remain
