Last week Sir Patrick Vallance, the UK’s chief scientific adviser, was publicly pilloried for seeming to suggest that the way to manage the coronavirus pandemic was to rely on herd immunity.
No matter that that’s not actually what he said, that’s what was heard. So what do we mean by herd immunity?
In brief, it means that if enough people are immune to a disease, then it becomes unlikely or unable to spread through the remaining vulnerable members of the community.
Sounds simple enough, and sometimes it is.
Take measles, for example. It’s a highly infectious disease that spreads very quickly amongst populations with no immunity.
As it’s such an infectious agent, to prevent measles spreading through a community requires rates of immunity of 90-95% (other less infectious agents, as coronavirus seems to be, may be contained with lower rates of herd immunity).
In modern society, most of that immunity comes from vaccination, rather than native disease. The effectiveness of herd immunity in measles relies on a couple of factors:
- Immunity, whether from disease or vaccination, is usually lifelong. Antibody levels mostly stay high throughout life, conferring long term protection.
- The measles virus itself is stable — that is, it doesn’t mutate into different strains. Your immunity today is not suddenly going to become ineffective next week. Once a measles always a measles.
Sadly not all viruses are so well behaved, nor are our immune systems so efficient. Flu viruses for example obey neither of the measly rules: immunity from flu vaccination is often short-lived, sometimes only months, and not only are there multiple flu strains around, but they’re very good at mutating into different strains.
That’s why we have an annual flu vaccination program, and each year with different viral strains.
As for COVID-19, it’s too early to tell. It’s very probable that, as with other coronaviruses, immunity, whether from infection or any future vaccine, will not be life long. Coronaviruses are generally also a wily bunch, pretty good at mutating.
What you see this year may not be what you get next.
So I can’t see how herd immunity on its own is a viable option for “managing” COVID-19. A vaccine is at least a year away, so infection is currently the only way of developing immunity.
And as we now know, infection means death for a certain percentage. Whether that percentage is three, one, 0.1 or lower, for a virus that is likely to infect tens, if not hundreds, of millions, that’s a lot of deaths.
That doesn’t make herd immunity irrelevant. As communities experience the virus and develop at least some level of immunity, it will eventually slow the spread. But no strategy that goes like this gets my vote:
- Nasty virus, help, what to do?
- Herd immunity is our saviour, let everyone get it as quickly as possible.
- OK, so quite a few (well, actually, quite a lot) will die, not to mention the health system being overwhelmed. Oh, and the morgues. But it’s mainly the old and sick, not me.
- Wait a long time, hopefully get a vaccine. Boost herd immunity.
- Hope immunity lasts/vaccine works/virus doesn’t mutate.
- Really hope this last bit is true.
- Problem solved.
Hence most countries have accepted that waiting is not a viable option, and that strong measures are needed to reduce the rate of spread now.
This slowing will allow health services the time to develop capacity and deal with patients over a longer period, rather than being overwhelmed by a sudden and severe spike in demand.
Which in the end is pretty much what Sir Patrick and Boris ended up saying in their address about “herd immunity”. Bet they wish they’d said it up front.
Dr Nick Carr is a Melbourne-based GP, author and broadcaster. His interests include the care of the elderly, psychological medicine and paediatrics.
No.
Measles mutates, but the measles vaccine remains effective because the target, the antigen, the measles vaccine aims at is vital for the measles virus to infect and spread from person to person. Influenza also mutates, and the target of the influenza vaccine is the head of the haemagglutinin molecule (which allows the virus to get into the cell), and which does rapidly mutate. But it’s the stalk of the haemagglutinin molecule that’s necessary for infection to occur, and that part doesn’t mutate (and isn’t targeted by immunisation).
Coronaviruses are unique amongst single stranded RNA viruses (which influenza viruses are too) in having an exoribonuclease, which proofreads RNA replication making it of relatively high fidelity. Based on the rate of mutation in other single stranded RNA viruses, all the known coronaviruses arose less than 10,000 years ago despite being around for tens of millions of years.
COVID-19 won’t mutate. If there’s another coronavirus epidemic in a decade or so it will be a different species not a mutated strain, just like the SARS virus was a different species to COVID-19.
It’d be really triffic if the medical community could get their flippin’ ducks in a row.
Doc Carr here suggests immunity is possible from becoming infected with the coronavirus, but goes on to say that he;
“…….can’t see how herd immunity on its own is a viable option for “managing” COVID-19. A vaccine is at least a year away, so infection is currently the only way of developing immunity.”
Whereas, when the President of the British Society for Immunology wrote to the British Health Secretary, and CMO, he suggests any such prospects for immunity developing from infection are a crock;
From The Age on Monday, in an article headed;
“Backlash as British experts say herd immunity policy may have ‘severe consequences'”
“….In a letter to the Health Secretary, Sir Patrick and Professor Chris Whitty, the government’s chief medical officer, the British Society for Immunology (BSI) warned there could be “severe consequences” of infecting large numbers of people when knowledge of the virus was still so limited. “We don’t yet know if this novel virus will induce long-term immunity in those affected as other related viruses do not,” said Arne Akbar, the society president. “Therefore it would be prudent to prevent infection in the first place.”
Simply put, they have no clue if long term immunity is possible with this particular virus, but they do know those affected with similar viruses do not develop such immunity.
It was that letter from “Arne” that drove BoJo and Co into frantic backpedalling.
And, yesterday, up popped the Netherlands PM, Rutte, proposing an ever so slightly varied version of the original BoJo & Co ‘plan’.
Create enough noise, and imbeciles will grasp at ridiculous options, usually because the viable options, that do the least harm, are simply beyond their capacities to get their heads around.
SARS coronavirus infection resulted in immunity in the 90% of those infected and who didn’t die. There’s no human carriers of SARS virus to make SARS endemic.
Why should COVID-19 coronavirus be any different?
Now, who to listen to?
A Crikey subscriber, or the President of the British Society for Immunologists?
Spare me, Wayne!
You are just too damn ‘noisey’.
https://www.theatlantic.com/health/archive/2020/03/coronavirus-pandemic-herd-immunity-uk-boris-johnson/608065/
Extract:
“When people are infected with OC43 and HKU1—two other coronaviruses that regularly circulate among humans and cause common colds—they stay immune for less than a year. By contrast, immunity against the first SARS virus (from 2003) holds for much longer. No one knows whether SARS-CoV-2 will hew to either of these extremes, and according to one recent study, its behavior could mean anything from annual outbreaks to a decades-long quiet spell.”
The common cold is one of only 6 coronaviruses that humans have ever encountered. Of those 6, no vaccine has ever been found.
100+ years of research with no vaccine, in spite of the huge dollars potentially available. If they find a vaccine in 18 months I’ll stop commenting on Crikey.
There’s actually 7 human coronaviruses:
https://www.cdc.gov/coronavirus/types.html
MERS, SARS and COVID-19 are zoonoses (they came from other animals).
There’s around 200 different viral types that cause the common cold. Rhinoviruses account for around 30-40%. There’s so many, developing a vaccine is impractical.
‘Herd immunity’ is an Orwellian euphemism, one worthy of boris johnson at his most evil. It is simply the continuation of Britain’s Austerity by other means. Johnson’s policy is to let the coronavirus spread because he is happy to murder the elderly to save money. As it is, Austerity there is murdering 39,000 Britons a year without complaint or even recognition.
In Washington State, nearly all the deaths reported have been associated with nursing homes.
Same here. Misgovernment politicians and “The Australian” would wax lyrical about the need to first reduce the Demon Deficit, while themselves continuing to cut billions from States’ health funding and sweating blood to gift vast tax cuts to their transnational mates and potential employers. morrison actually told the States during the 2019 election that there will be no extra money for State services for us. Nor any return of the $80 billion in hospital and school cuts announced in abbott’s 2014 Austerity Budget.
Stresses on the public hospital system, emergency services, and the lack of hospital capacity are all waved away. Ambulance ramping was openly instituted by the politicians as a normal and acceptable remedy! They even expect praise for it from the business community.