The government’s COVID-19 strategy since the announcement of their updated roadmap in February of this year, has been to lock the country down until the vaccines arrived. Once we had jabs in arms, we could reopen society and life would get back to normal again.
The strategy was predicated on the concept of ‘Herd Immunity’ – a state in which a sufficient proportion of the population is immune to the disease, thereby preventing further waves taking hold, and finally ending the outbreak.
The Herd Immunity Threshold
The ‘Herd Immunity Threshold’ (HIT) is the percentage of the population at which herd immunity has been achieved, and it is related to the contagiousness of the disease.
The ‘Reproductive Number’ (R) of a disease is the number of people each infected person is expected to pass the virus on to, on average. It is a measure of the disease’s contagiousness, but it can also tell us about the nature of the outbreak. When the R number is above 1, the outbreak is growing. When it is below 1, the outbreak is shrinking.
The promise of herd immunity is that it can guarantee the R number will be kept below 1 and therefore, that the outbreak will eventually extinguish itself.
The HIT is a function of the R number, and it is quite easy to calculate: HIT = 1 – (1/R).
Pandemic influenza has an R number between 1.5 and 2 (we’ll say 2 for convenience), so an infected person would pass the virus on to 2 new people, on average, and its HIT would be 1 – (1/2) = 50%. So, once 50% of the population had been vaccinated, each infection would generate less than one new infection, on average, and the outbreak would steadily peter out. Job done.
What Is The Herd Immunity Threshold For COVID-19?
To calculate the HIT for COVID-19, we need to know COVID’s R number, and that’s when things could get a little tricky. In reality, the R number isn’t a fixed parameter of a disease. It is determined by many other variables and it evolves over time. Fortunately, in the context of this piece, that discussion is academic – in both senses of the word – so we can proceed with sample numbers.
Estimates of COVID’s contagiousness from the first half of 2020 put the R number somewhere between 2 and 4. If we took the midpoint of that range, the HIT would be 1 – (1/3) = 67%. Had I been infected with this virus, I would have normally passed it on to 3 people. If 67% of those people are now immune, I can only pass it on to one of them. The outbreak has been stopped, and everyone can get on with their lives.
Since then, more contagious variants have come along, and they naturally became dominant. The latest and most contagious is called the Delta variant, and recent estimates put its R number somewhere between 5 and 9. Taking the mid-point again, the HIT for Delta would be 1 – (1/7) = 86%.
Whether the true R number is 5 or 9 or anywhere in between, we can see that it would take a lot of vaccinations to reach the HIT for this variant. For most populations, such a high threshold would mean that almost everyone would need to be vaccinated for a herd immunity strategy to succeed.
And that realisation takes us away from basic mathematics, and into the realm of ethics.
Should you sign your kids up for a vaccine with a very short track record? Or do you let your kids become a vector for a disease which poses little risk to them, but a much greater risk to their grandparents?
Should vaccination be mandatory for all adults? And what punishments would be appropriate for conscientious objectors?
We know where the establishment stand on the matter – though I’m not sure they were ever burdened by these ethical considerations. A process of coercion has been initiated, and it will continue for the foreseeable future.
But the establishment has a problem: their strategy is almost certain to fail. The HIT for COVID-19 is a moving target, and it’s moving further and further away. In fact, it may already be out of reach.
To explain why this is the case, I’ll have to admit something: I made an assumption in my earlier calculations which I knew to be false. Did you notice it?
I implicitly assumed that the vaccines were 100% effective, conferring perfect immunity. But we know that’s not true, and we’ve known that since the first reports from the Phase 3 trials came out, towards the end of 2020. Moderna and Pfizer were reported to be 90%+ effective, which is very encouraging, but it isn’t perfection.
Granted, the vaccines don’t need to be perfect for a herd immunity strategy to work, but it does change the calculations.
Our new formula for the HIT is = (1/E) * [(1 – (1/R)], where E is the effectiveness of the vaccine.
We can rephrase this as New HIT = (1/E) * Old HIT.
Assuming E = 90%, the effectiveness adjustment is (1 / 90%) = 1.1, and the new HIT for Delta is 1.1 * 86% = 94%. So we will need to vaccinate 94% of the population to reach herd immunity from COVID-19
Does that sound like it would be possible?
After allowing for exceptions and exemptions, is it possible to vaccinate 94% of the population? If it was, then it would give the establishment reason to bully and shame every single one of us into taking the jab, but, is it feasible in practice? And even if we did reach that threshold, would we be sure to have achieved true herd immunity?
No, we wouldn’t, because the true HIT probably isn’t 94%. There was another mathematical sleight of hand. (Last one!)
Herd immunity can only be achieved by reducing transmission to the point where the ‘post-vaccination’ R number is less than 1. That means we need to know how effective the vaccines are at reducing transmission, not hospitalisations or severe disease.
It is very important that we don’t conflate all forms of effectiveness into one, as there are multiple axes along which a vaccine could be said to be ‘effective’, and this mistake is easily made by the public, media, and politicians alike.
So, how effective are the vaccines against transmission?
We don’t know, and we won’t know for many months. Transmission can only be estimated through observation of large datasets, over time – which is why it wasn’t reported as part of Big Pharma’s initial Phase 3 results.
To underscore the current paucity of knowledge on the matter, the latest estimates range from the mid-teens to the mid-90s. Given that this variable is bounded between 0 and 100%, we could barely say less.
What we do know, is that many of the countries with the highest vaccination rates are seeing spikes in transmission, notably Iceland, Singapore, Israel, Malta, and Gibraltar, so effectiveness is clearly not 100%. Beyond that however, it’s difficult to say anything with confidence.
Rather than arguing over which estimates we like the best, let’s look at the problem from a different perspective.
What Would It Take To Get To Herd Immunity?
The HIT is a function of the basic reproduction number of the disease (the R number when everyone is susceptible and there are no public health interventions in place) and vaccine effectiveness against transmission. Using this information and the formula for the HIT, we can create a table showing us which combinations of contagiousness and vaccine effectiveness will allow us to get to herd immunity.
The first, and most obvious, observation is that herd immunity is impossible for most combinations.
Vaccine effectiveness will need to be very high for this strategy to stand any chance of success but, as we know, the vaccines are not 100% effective against transmission, so that rules out the bottom row.
A recent estimate of the basic reproduction number for the Delta variant from the CDC put it between 5.0 and 9.5, which means we can cross out the first three columns too.
That doesn’t leave us with many good options.
We can summarise the remaining possibilities as follows: in order for herd immunity to be even a theoretical possibility, we would need all vaccines to be well over 80% effective against transmission, and we would have to hope that Delta’s basic R number was closer to 5.0 than 9.5. We would also have to hope that no new variants came along that were more contagious and / or more resistant to the vaccines.
In other words, even if we vaccinated 100% of the population, we would still have to cross our fingers and hope that all of the vaccines and the variants played ball for our herd immunity strategy to succeed.
But, hope is not a strategy. Hope is not scientific. You do not force novel pharmaceuticals on a population in the hope that they can do what you need them to, nor in the hope that the virus will play ball. Betting our national public health response on the behaviour of a virus that has disappointed us at every turn, is the complete opposite of sound, sensible policy-making.
Herd immunity might be a possibility in a theoretical analysis like this, but as a real-world strategy, it is hopeless.
Does Herd Immunity Even Matter?
The more people we vaccinate the better, so who cares whether we reach herd immunity?
OK, let’s think about that scenario.
If 100% vaccination can’t get the R number below 1, then the virus will continue to spread until the whole population has eventually been exposed to it. The vaccines will offer some protection to those who need it most, but even a vaccine that is 95% effective against hospitalisation and serious disease would still lead to thousands of deaths and a serious strain on our health care system.
That, I think, is what Philip Nolan was trying to say in this tweet. His calculations may have been incorrect, but this was the scenario he was preparing us for.
Moreover, with developed nations around the world taking the same approach and betting it all on vaccination, the virus will continue to circulate, maintaining the global breeding ground for the variants which could erode the vaccines’ real-world effectiveness.
Remember, this is a situation where a few percentage points can make a lot of difference. A variant that reduces vaccine effectiveness against hospitalisation from 90% to 80% doubles the risk of hospitalisation from 10% to 20%.
How do you think Ireland’s policy-makers would respond in that scenario?
The common-sense reality is that, whether we vaccinate 60% of the population or 100%, this virus is too contagious for the vaccines to permanently suppress its transmission through herd immunity.
The government knows this. NPHET knows this. ISAG knows this. (The media is slowly catching up.)
Why Are They Forcing The Vaccine On Us?
So why are they bullying us into taking a vaccine with a very short track record, when the goal of their vaccination strategy is already out of reach?
What argument can there be for vaccine passports, when we don’t know how well the vaccine protects us from each other?
Why are they splitting society in two over a strategy that can’t end the restrictions on our social and commercial lives?
So yes, it does matter whether we reach herd immunity, because the costs of this strategy are growing by the day.
The Problem Is Transmission; It Was Always Transmission
Perhaps the most important question of all is, given that transmission would still be a problem post-vaccination, why didn’t the policy-makers just focus on transmission in the first place?
Why have they chosen to take the nation down this divisive path when there are other, non-invasive options which better address the root cause of our trouble – the virus – and which they have hitherto neglected?
For example, Ireland has never had a functioning contact tracing system. Tracing contacts for COVID-19 requires 14 days of backward tracing, yet until March 2021, Ireland’s system only backward traced for 2 days! This approach might hope to trace 30-40% of an individual’s contacts, but that leaves the remaining 60-70% unaccounted for, making a farce of our policy-makers’ suppression efforts.
As things stand, the system still only backward traces 7 days. Wouldn’t it make more sense to plug that hole first before we start injecting the whole population with experimental vaccines?
Our policy-makers’ efforts with testing were even less distinguished. They never experimented with population-wide testing, despite many international efforts to draw upon, while NPHET’s rejections of the various use cases for rapid antigen testing won them scorn at home and abroad.
The ability to test a population is not affected by geography, borders, law, finances or any of the usual excuses. It is purely about ambition and competence, and on those accounts our policy-makers have once again come up short.
Testing and tracing are purpose-built to find infections, to cut chains of transmission and to keep clusters suppressed so that they cannot form community outbreaks. They are standard epidemic risk control measures, yet our policy-makers have all but ignored them, leaning instead on lockdowns, and now vaccines, as their primary policy tools.
History Will Not Be Kind To Them
The medical community has been patting itself on the back since Pfizer and Moderna released their preliminary Phase 3 trial results. Maybe these vaccines really are the medical marvels they say, but no amount of backslapping can hide the fact that they cannot prevent infections, they cannot achieve herd immunity, they cannot lift the restrictions from our lives, and they cannot do the job that had been promised of them over the last year.
Nor can they heal the damage that the establishment’s authoritarianism is doing to our society, and to the community and the culture which holds us all together.
Transmission was always the problem we needed to solve, because preventing transmission prevents hospitalisations, ICU admissions, longCOVID, mass unemployment, social disorder, and every other malady now affecting our nation. Policy-makers should have focused on transmission from the start and throughout, and if they had, they could have solved this problem long ago. Instead, they bet it all on lockdown, PCR tests and vaccines, and every one of those measures has failed.
And that is what the historical record will show.