by Andrew Lilico
Monday, 22
November 2021
Explainer
07:00

What does waning immunity mean for the long term?

Reaching endemic equilibrium with Covid will have some bumps along the way
by Andrew Lilico
Credit: Getty

‘Waning immunity’ is a phrase we hear often, but what exactly does it mean? There are three different forms: waning of infection-acquired immunity against contracting the disease; waning against vaccine-induced immunity against contracting the disease; and waning against protection (from either vaccination or prior infection) from risk of severe disease, hospitalisation or death.

Infection-acquired immunity from contracting Covid is expected to wane over time, as happens with other coronaviruses. This is a process additional to that of “breakthrough” re-infections. The latter occurs because immunity from contracting the disease is (assuming the first infection is mild enough) not perfect to begin with. So, even within a few months of an initial infection, the risk of re-infection is cut by only some 70-80%. 

(We should note in passing that this 70-80% figure might be to some extent a reflection of new variants partially escaping the immunity conferred by infection with an older variant. So, perhaps having had the alpha variant — the thing we used to call the “Kentish Variant” — confers only 70% immunity against infection with the now-dominant delta variant, but maybe the protection from infection with the same variant is higher.)

Waning is different from breakthrough. With waning, coronaviruses cunningly make the immune system forget them over time, so within perhaps two years or thereabouts people can get infected again fairly easily.

Absent boosters, waning would, along with immigration and new births, become a key factor in the endemic cycle for Covid. It would imply a lot more infections than is commonly grasped. The delta variant has a herd immunity threshold of about 85%, so in a stable endemic equilibrium we’d need about 85% of the population to be immune, on average, over time. For simplicity, let’s ignore non-immune immigrants and babies and just focus on a stable population, assuming we’re at the herd immunity threshold to begin with. If immunity waned gradually over two years, then for every individual among the 85% immune that lost immunity over that two years, another individual would have to become immune.

If each new infection created one extra immune person, that would mean we’d have to infect 85%of the population over a two-year period. In England there are 56 million people. So to infect them all over two years we’d have to infect about 77 thousand per day. If an infection actually only creates 70-80% of an immune person (as per the breakthrough infections discussed above), that 77 thousand per day would become 96-110 thousand infections per day. So to maintain the herd immunity threshold at 85% of the population we’d need to have about 65 thousand infections per day if each infection creates one immune person, or 81 to 93 thousand infections per day if the average infection creates 0.7 to 0.8 immune people.

It is of interest to compare that to the current level of confirmed cases. At the time of writing there are about 30-35 thousand confirmed cases per day and it is believed the ascertainment rate (the share of infections that are detected) is about 40-50%. So 30-35 thousand cases means about 60-88 thousand infections per day. In other words, we are current at about, or slightly below, the level of cases there would be in that endemic equilibrium.

Now waning from natural infection is unlikely to be as smooth as that. Even in the longer-run there may be some seasonality in infections. But the bigger factor in the nearer-term is that infection came in waves, so it is quite likely that the waning of infection will come in waves as well. The initial set of infections, covering some 10-12% of the population, occurred in or around March 2020. If waning occurred instantly, two years after initial infection, we’d expect a (modest) waning-induced wave of infections next Spring, then another wave in November/December 2022, and so on. Of course, waning will not be as instant as that, but the essential point remains that the process of getting to our ultimate endemic equilibrium may proceed via some bumps, with mini-waves echoing the timing of the initial waves during the epidemic.

A further reason things may not proceed as discussed above is that not all of us acquired our immunity via infection. Only around half the population of England has been infected, according to the University of Cambridge’s MRC Biostatistics Unit. By contrast, nearly 90 per cent of those over 12 have had at least one dose of a vaccine.

At one stage it had been hoped that vaccine-induced immunity might be longer-lasting than infection-acquired immunity (because the waning of infection-acquired immunity occurs through processes the disease induces in the body that the vaccines do not). But studies conducted since mass vaccination has occurred suggest the opposite. It appears to be vaccine-acquired immunity that wanes more rapidly. In some studies, around 50% of inwards transmission protection is estimated to be lost after about six months. Some analysts suggest that may be an over-estimate, as it has proven difficult to control very well for the effects of unconfirmed cases (boosting the immunity of the unvaccinated) and of the takeover by delta during the analysis periods (with delta having higher transmissibility and some vaccine transmission protection escape). But even if it does eventually prove to be an over-estimate the point remains that vaccine-acquired immunity may wane more rapidly than infection-acquired immunity.

Many people now have ‘hybrid immunity’ (immunity from having been both vaccinated and infected), which is expected to be quite long-lasting, and an increasing number have had a third booster dose (particularly older people — for whom vaccine waning appears to be slightly more rapid), which may not wane in the same way. Furthermore, just as those who get breakthrough infections despite double vaccination are not as infectious to others as unvaccinated infected people, the same may be true of those infected after waning. If infectiousness after waning is reduced, the herd immunity threshold may be cut a bit so the equilibrium level of daily infections may be lower.

For now we have a significant portion of the double-vaccinated-but-not-yet-infected population for whom waning may occur more rapidly, perhaps over the next few months. Indeed, some modellers suggest that vaccine waning may have been a factor even in the recent evolution of cases since July, perhaps explaining why cases overall have roughly plateaued (albeit with cycles around the average) since then and in particular why cases in older people started to rise in the month or so before the booster campaign really got going.

Vaccine waning could make a waning-induced wave early in 2022 a bit larger, by combining the waning of 2021 vaccines with the waning of 2020 infection-acquired immunity.

This analysis might seem concerning. After all, I’ve argued that even the average level of cases over the long-run might be higher than those we’ve had recently. And the latest cases have been heavily concentrated amongst low-vulnerability children, whereas the case numbers in my analysis above would be more evenly spread across the population. So it might seem like I’m suggesting there’ll be an awful lot of hospitalisations every year, forever.

There are four reasons things may not be as bad as they seem.

First, although the transmission protection of vaccines and infection-acquired immunity fades fairly rapidly, protection against severe disease, hospitalisation and death are expected to last much longer — indeed, for decades — apart perhaps from some of the most elderly and others with weakened immune systems at whom the initial booster campaign was targeted. Second, there is a view that the protection from serious disease continues to increase (albeit more gradually) even after the big jump from the first infection. Once we’ve all had Covid three or four times, our immune systems may be so used to it that it will be dangerous for relatively few of us. Third, there are new highly-effective treatments coming on stream that appear to eliminate the vast majority of hospitalisation and death risk even if they are taken after people have contracted the disease. And, fourth, as with flu, more vulnerable people are likely to take annual (or perhaps six-monthly) booster jabs, which will doubtless become customised to whatever variant is circulating at the time, keeping their immunity high.

So the pattern one might expect is as follows. We’ve now completed what one might call the ‘epidemic phase’ of the disease — the stage at which cases, hospitalisations and deaths could grow exponentially, in the way that they did in March 2020, November/December 2020 and May to July 2021. With schoolchildren, the final set of immune-naives, being infected in September/October 2021, we’ve shifted from that epidemic phase into a phase of transition between the epidemic and the long-run endemic cycle. That transition phase may be bumpy, because immunity may wane in a bumpy way, possibly creating new mini-waves of during 2022. But even these should produce relatively few hospitalisations, and over the longer term hospitalisations will probably drop further.

The policy upshot of all this is fairly straightforward. Boosters for the vulnerable; new therapies as they become available; no need for any restrictions such as mandatory social distancing or masks; encouragement of a modicum of common-sense and courtesy towards others if new waning-induced waves come next spring, but no more; and a ramp-down of testing in schools, isolation requirements for the unvaccinated and remaining rules for travellers.

Waning is an issue that public health officials will grapple with, as they do for other diseases. But as a grand policy question, Covid is finished and waning will not change that.

Join the discussion


To join the discussion, get the free daily email and read more articles like this, sign up.

It's simple, quick and free.

Sign me up
Subscribe
Notify of
guest
24 Comments
Most Voted
Newest Oldest
Inline Feedbacks
View all comments
Jonathan Ellman
Jonathan Ellman
10 months ago

It seems that delaying coming out of lockdown earlier this year as soon as the elderly and vulnerable were vaccinated was a big mistake from the point of view of acquiring herd immunity. More healthy young people would have gained immunity from infection and we’d be months further towards to herd immunity than we are now as winter approaches.

Last edited 10 months ago by Jonathan Ellman
Matt M
Matt M
10 months ago

If I understood this, Andrew Lilco is saying we are now at a steady state of infections and will see dips and spikes in numbers of cases over the coming years due to the effects of waning immunity.

Did I read that right?

If so, it seems the emergency is over. Vaccines, infection- induced immunity and improved medical treatments have turned an unknown virus into just another risk of life.

So why are they locking down in Europe? It doesn’t make any sense.

Last edited 10 months ago by Matt M
Elaine Giedrys-Leeper
Elaine Giedrys-Leeper
10 months ago
Reply to  Matt M

As of November 17, at least in Salzburg, their staffed ICU beds (including their surge capacity beds) were almost fully occupied with Covid patients – they were preparing to triage for ICU admissions.
The Austrian health authorities were concerned that this situation would not just be confined to Salzburg as winter progresses.
Across the various states in Austria between 57% and 70% of the population have been fully vaccinated so plenty of “dry tinder” for the virus to burn through here.
In Belgium they are expecting their case peak around the end of November / begining of December and they too, have a developing problem of not having enough staffed ICU beds….and so it goes on.

Chris Wheatley
Chris Wheatley
10 months ago

Exactly, and thank you. If you read some comments you get bored with individuals who are too clever to get Covid.

Hardee Hodges
Hardee Hodges
10 months ago

Please understand that hospital policy nearly everywhere seeks for 80% ICU use. Staffing is a universal issue. Somehow, they manage to cope. And some are near death’s door with Covid as the last straw.

Galeti Tavas
Galeti Tavas
10 months ago

Come on – you never said what waning immunity means for the long term. You told us a lot of ‘The Science’ collected data, which as we know is completely just data which agrees with the agenda… You gave us guesstimates and things like natural immunity may last 2 years at some OK percent wile vaccines last 6 months – But…

Injecting those ‘toxic’ spike proteins – that may not be so good every six months, and the biggest thing – medicines. WHICH already seem to exist, although the agenda forbids their study or usage.

Ivermectin, Fluvoxamine, and more, even a couple newer studies are saying the dreaded MAGA hydroxychloroquine may have some edge, and Querctin too, possibly – and Zinc, and according to Dr Campbell – Vitamin D may actually 100% stop deaths in all the the most severely comorbidity. ( https://www.youtube.com/watch?v=V5g9AVqRsjo Then the $700 Pfizer pill (may have side effects which the above do not, having been given Billions of doses)

So what does it mean for the long term???????????????? You never said.

To me it means use common sense, get a vax if you are of great danger, otherwise use medicines and natural immunity and get back to work and stop printing $$$$$$$ and destroying the global economy, destroying mental health, physical – non covid – health, and education and small business, and stop killing third world babies by impoverishing their parents through reduced economic activity in the West.

chris sullivan
chris sullivan
10 months ago
Reply to  Galeti Tavas

Good summary thanks

Jürg Gassmann
Jürg Gassmann
10 months ago

The spectre that has been raised is that the shots undermine the immune system’s ability to adapt to new variants, so that rather than have “hybrid immunity”, the jabbed have compromised immunity.
That is the scary proposition. And only time will tell.

Julian Farrows
Julian Farrows
10 months ago
Reply to  Jürg Gassmann

I’ve taken the vaccine too, but am worried about comprising my own immunity. I wish I hadn’t taken it. I feel more at risk now than I did beforehand.

Hardee Hodges
Hardee Hodges
10 months ago
Reply to  Julian Farrows

Many are in the same place contemplating the booster. As vaccine breakthrough cases begin to outnumber naive infections, it’s a worry anew. Seemingly, the vaccinated are spreading more because their symptoms are mild and they think not serious.

Chris Wheatley
Chris Wheatley
10 months ago

What a dull article!! It doesn’t do more than state the obvious. Developers of flu vaccinations spend all of their time predicting the format of the next strain. Over-70s get a free shot of this ‘best guess’ if they want it. Meanwhile we have built up a semi-resistance to flu in that we don’t all get very bad symptoms.

When the Spanish invaded South America they wiped out huge numbers of the indigenous population with ‘harmless’ things like measles. Presumably, the survivors still get measles but it is no longer a killer.

Elaine Giedrys-Leeper
Elaine Giedrys-Leeper
10 months ago
Reply to  Chris Wheatley

“Presumably, the survivors still get measles but it is no longer a killer.”
Presumably because the MMR vaxx rates in S America are in the 80 – 100% league except for basket case states like Haiti and Venezuela.

Chris Wheatley
Chris Wheatley
10 months ago

Hmm. I don’t really agree with this. When I was young literally everybody had measles and I don’t remember anybody dying. The MMR vaccine came later. Do you have stats from measles deaths in South America pre-MMR?

Elaine Giedrys-Leeper
Elaine Giedrys-Leeper
10 months ago
Reply to  Chris Wheatley

No stats that I can find for S America but there are for the US. From the CDC :
“In 1912, measles became a nationally notifiable disease in the United States, requiring U.S. healthcare providers and laboratories to report all diagnosed cases. In the first decade of reporting, an average of 6,000 measles-related deaths were reported each year.
In the decade before 1963 when a vaccine became available, nearly all children got measles by the time they were 15 years of age. It is estimated 3 to 4 million people in the United States were infected each year. Also each year, among reported cases, an estimated 400 to 500 people died, 48,000 were hospitalized, and 1,000 suffered encephalitis (swelling of the brain) from measles.”… “Measles was declared eliminated (absence of continuous disease transmission for greater than 12 months) from the United States in 2000. This was thanks to a highly effective vaccination program in the United States, as well as better measles control in the Americas region.”

Chris Wheatley
Chris Wheatley
10 months ago

Of course, I bow to your stats. I just find this difficult on a personal basis. Here in the 50s and 60s if a child had measles you encouraged your child to play with them to get it out of the way.

I suppose that we were healthier in 1912 than the USA. I remember reading about the drive to get people there to get vaccinated against typhoid. Most rich and middle-class people refused and the poor people died. Not really making a racist point, the poor people tended to be of different races.

I was around in 1963, although very young, and I just don’t remember that here. I was shocked when I heard that the MMR was being introduced.

Lesley van Reenen
Lesley van Reenen
10 months ago
Reply to  Chris Wheatley

We were also sent to play with children infected with a variety of childhood diseases. It was the way. Somehow I never got mumps and whooping cough (that I know of).

Andrew Fisher
Andrew Fisher
10 months ago
Reply to  Chris Wheatley

It is slightly depressing that the common reaction to almost every article is either splenetic rage or an affected boredom! It might be stating the obvious to you, but if so though it is surprising there are so many different views and responses to covid!

Galeti Tavas
Galeti Tavas
10 months ago
Reply to  Chris Wheatley

“What a dull article!!”

“If you read some comments you get bored with individuals who are too clever to get Covid.”

I know I am a covid bore, but the response has hugely messed with me, the resulting inflation is eating my life savings as I am scared of the Stock market with its crazily inflated prices from the insane fiscal and monetary ‘stimulus’ (and my gold/silver stack is doing nothing) – and I have been blocked from returning to London, and as I am a conscientious objector and will not vax, it may keep me out of my old home for ever…. (I am only against the vax because mandates; the gov.s have used this excuse to make totalitarian states out of once free ones), and are out to destroy the free world using “President Obama: Never Let A Good Disaster Go To Waste”

Chris Wheatley
Chris Wheatley
10 months ago
Reply to  Galeti Tavas

I truly sympathise with you and can see where you’re coming from. To me your posts are great and full of energy.

My problem with all of this anti-vax anger is that I only see it on UnHerd. I hear about a riot in the Netherlands but it was a very small riot. More fuss has been caused by the police than by the rioters.

Where I live (city of 300,000) almost everyone I meet has had the two doses and some, like me three. None of my colleagues or acquaintances have any doubts at all about vaccination. But on UnHerd there is terrible anger and it gets caught up with FOTI – freedom of the individual. I just can’t see this. Our city is not 300,000 individuals – it is a community and everybody is connected to everybody else. If the medical professionals and the city elders and the teachers and the fire brigade and the labour unions and family and friends all believe that vaccination is right for all – then it is the only way. In any crisis, if there are a few who do their own thing, everybody fails. It is all or nothing.

I am now being boring so I am off to bed.

Iris C
Iris C
10 months ago

A large number of people have T cells which latch on to Covid virus and destroy them, giving complete protection and, unlike the asymptomatic, they cannot infect others..
There are also a small number of people who are genetically immune.
This information came from Healthcheck on Worldservice (18th November at 09.32) and an article in “Nature”.
Blood samples were taken from Covid nurses in a London hospital before the pandemic took hold and it is hoped that future blood samples will give an indication as to why some of them did not become ill.
Also, interestingly, there does not seem to have been any substantial increase in hospitalisation or deaths after the Lord Mayor’s parade in London on the 13th (no masks) and the 4,000-strong march past the Cenotaph on Remembrance Sunday – mostly elderly and without masks. . .

Lindsay Snoman
Lindsay Snoman
10 months ago
Reply to  Iris C

My son has managed to not pick up Covid despite me getting it (double jabbed), his sister getting it a month after me (she has had one jab) and when my husband brought it into the house at the beginning of the pandemic (he infected me and daughter so we have had it twice now). Son has type O blood, which could be a factor but he also has Psoriasis and I have wondered if that is why he keeps dodging the covid bullet.
I think there is a lot more going on that no-one really know which effects severity and immunity.
I also dont understand why the government is forcing mandatory vaccines into social care when they have just ok’d a tablet treatment for covid?!? Especially, as I can attest, the vaccines dont stop you from getting covid! (I picked it up 3 months after 2nd vaccine).

Hardee Hodges
Hardee Hodges
10 months ago
Reply to  Lindsay Snoman

There are those who will not get ill proven by early data from the Princess cruise ship and USN ships. Odd that we never have tried to discover the reasons.

Galeti Tavas
Galeti Tavas
10 months ago
Reply to  Iris C

World-o-meters, deaths per million from the China Virus

China, 68

Vietnam 243

Taiwan 36

USA 2379

UK 2105

https://www.worldometers.info/coronavirus/#countries

Yes it is like the New World when the Westerners arrived – no natural immunity, but it is the Westerners getting hit on this one. Odd how a lab produced thing ends up like this…..

Billy Bob
Billy Bob
10 months ago
Reply to  Galeti Tavas

Some rather cherry picked statistics there though, as Vietnam and Taiwan both had very strict border policies that largely kept the virus at bay, and I wouldn’t trust the Chinese stats as far as I could throw them.
Western countries also test much more than developing ones, so therefore their numbers are always going to be higher especially when the UKs Covid deaths include anybody who had the disease in the 4 weeks before death, whether or not it was Covid that actually killed them