Herd Immunity Of Covid In UK

Herd immunity is something that’s been mentioned in the press from time to time but no one seems to have given us examples of what exactly this might mean in terms of infections, deaths, timescales and so on.  All we’ve been told is – ‘millions will die!’ which kind of closes the argument down because none of us want to go there.

BUT.  Think about it for a while.  The ‘mainstream media’ (everyone’s most hated group at the moment) have done a great job at scaring us all into staying at home with daily ‘deaths’ from Covid, graphs of infections and constantly whining on about a second wave.  They never do this when we have a really bad flu season.  Remember, advertisers use this technique. If they say the same thing enough times, repeat it over and over, and say things like ‘and of course we all know that…’ before repeating said mantra, that audiences start to believe it.  And here’s the thing.  Stuck indoors on lockdown what do we do?  We turn the telly or radio on to be force fed even more of their woke nonsense.  The cycle repeats itself… but I digress.

OK, let’s look at herd immunity.  First, what is it?

Well, it is generally accepted that when a critical number of a population (community or group) has been exposed to an infection (and gained a level of immunity) then a certain protection is conferred.  This is because the virus cannot find enough susceptible people to infect and keep spreading.  This slows or even stops the disease.  A good example is with the highly infectious disease, measles; where 95% of the population needs to be vaccinated (immune) and so the virus can’t get a foothold.  Of course certain groups of people let the side down by not getting their kids vaccinated (MMR) and then the disease returns.

The safest way to get herd immunity is through vaccination. But, you can also get natural immunity by contracting the illness and building an immune response to it.

So, in the absence of a vaccine how many people would need to catch the virus and how many would die?  Uncomfortable questions of course, and I’m certainly not advocating this approach but rather than bury our heads in the sand or worse still listen to the BBC, let’s do some maths for the sake of clarity.

OK, first up we need to have between 60% – 85% of the population to have caught the virus, recovered and become immune.  Although this is a global issue we’ll use the UK to illustrate the numbers.  We’ll also use 70%, which is somewhere in the middle.  OK, 70% of 67,879,245.  This comes to 47,515,471 people.

Next, we would need to know the mortality rate of Covid.  At the start of the outbreak figures of 3.4% were thrown around (which is frightening) but as we’ve learned more, the scientific community now thinks the figure is thankfully much lower.  The latest figure, estimated by CDC, is about 0.3%.  That is 3 deaths for every 1000 people infected.

Multiplying our figure for 70% of the population by this rate we get the following number of deaths that is needed for natural herd immunity:

47,515,471 X 0.3% = 142,546 deaths 

This is terrible of course but while the official death toll, at time of writing, is 43,550 we should at least realise that we are already 30% there.  If some estimates are to be believed though, there is a suggestion that we might have already had 50,000 – 60,000 deaths, then we’re actually over 38% of the way there!

As the government opens up more and more activities (especially in England) then we will probably see infections continue to occur throughout the year and into the next.  As awful as it is, we may end up getting natural herd immunity as a population (i.e. 142k+ deaths) before we get a viable vaccine!

Is there a silver lining in this at all?  Well, maybe.

There is another factor at play here and that is the anecdotal evidence that suggests many people believe they’ve already had Covid back in December 2019 / January 2020.  This would indicate an even lower mortality rate and mean we are much closer to natural herd immunity, which is all good.  It would also explain why we haven’t seen a second wave after all the protests and mass gatherings that the media are selectively failing to condemn.

Is there any crumb of comfort here?  Well, actually there is.  Doing the maths with a lower mortality rate, say 0.1%, (OK, I’m being very optimistic here) means we’ve more or less reached herd immunity already.  So if a treatment could be found, like using plasma or the anti-inflammatory drug Dexamethasone then we could reduce the numbers again.

However, there are other factors to consider.  CDC says that many deaths logged as ‘Covid’ were actually due to something else (e.g. flu).  This would mean less Covid deaths.  Lower mortality you ask?  Well maybe not, it might just mean fewer infections!  Then we would have to do the maths again.  Either way a lot of people are dying before we get herd immunity.  Another problem is that those isolating are often in a particular group (e.g. the elderly) and thus no-one is really immune within that group.  It would only take one infection to be devastating. We also have to realise that this is a global disease and movement of people into our own population could upset the balance of figures.

I suppose we won’t really know the full picture until the whole thing is over and we can take the politics out of the science but one thing that will help us decide who is right in the next few weeks is when the pubs reopen and drunk revellers start forgetting to socially distance and start coughing over everyone and everything.  Call me selfish but I’m glad England are doing this social experiment first.

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