begin quote from:
Coronavirus: World ‘nowhere close’ to herd immunity, says WHO
begin quote from:
It’s one of the hopes of the pandemic, but despite some cities having sky high infection rates, natural immunity may still be a vain hope.
Talk of vaccines is all the rage. But another much discussed, and very controversial, way out of the coronavirus crisis has been the concept of natural “herd immunity” where enough people become infected and then immune to COVID-19 that the virus struggles to infect anybody else.
Some analysis has suggested that could be achieved with as few as 20 per cent of people becoming infected.
But the World Health Organisation (WHO) has now poured cold water on the idea declaring we’re “nowhere close” to even the lower level of immunity via infection needed.
On Tuesday, the WHO’s Health Emergencies Program executive director Dr Michael Ryan said the focus should be on stopping transmission, not aiding it in order to get to a level of pack protection.
RELATED: Follow our live coronavirus coverage
WHO Health Emergencies Program head Michael Ryan has said the world in ‘nowhere close’ to herd immunity. Picture: Fabrice Coffrini/AFPSource:AFP
“Right now, as a planet, as a global population, we are nowhere close to the levels of immunity required to stop this disease transmitting,” he told reporters.
“We need to focus on what we can do now to stop transmission and not live in hope of herd immunity being our salvation.
“That is not a solution and it is not a solution we should be looking to.”
In a report from earlier this month, the WHO said globally it was likely fewer than 10 per cent of the population had detectable COVID-19 antibodies in their system.
“Worldwide most people remain susceptible to COVID-19 infection,” the organisation stated.
HOW PANDEMICS END
Whether herd immunity should be a strategy in defeating COVID-19 is one of the most contentious aspects to the pandemic response.
Pandemics come to an end through a number of ways: the virus can mutate into something less troubling or less infectious; a vaccine is found; or it works its way through so much of the population that there is either no one left to infect or those it has infected become immune and so, ideally, don’t pass the virus on.
The latter two are forms of herd immunity.
When a person becomes infected with a virus or is given a vaccine the body’s cells fight back against the intruder.
Some of these cells hang around as “memory cells”. These recognise the virus and, if it re-enters the body, it can quickly recognise it and bombard it with antibodies to neutralise the effects. The more effective the body’s defence, the more immune people are.
Analysis of patients with COVID-19 has found most have antibodies to the SARS-Cov-2 virus (the virus’ full name) in their systems. Those who had more severe symptoms generally had more antibodies and so would likely mount a more spirited defence should the virus try its luck again.
The issue with SARS-Cov-2 is, it’s still too early to tell how effective the body’s memory of infection actually is.
Is social distancing or a level of immunity preventing London’s COVID numbers from rising. Picture: Justin Tallis/AFPSource:AFP
“For COVID-19, we do not yet have enough data to confirm if antibodies protect, what antibody levels are required, or how long protection will last,” the WHO has stated.
“There is currently insufficient information to conclude whether people who have recovered from COVID-19 and have antibodies are protected from a second infection.”
Earlier in the pandemic, some countries toyed with the idea of simply letting coronavirus rip and developing herd immunity as quickly as possible. The UK backtracked on that plan and Sweden has denied it was ever the plan.
But the Swedish authorities have said herd immunity could be a by-product of its less stringent restrictions on movement.
That strategy has led to a high number of COVID-19 related fatalities. Sweden has seen 20 times the fatalities of its neighbour Norway which locked down harder and faster.
On the flip side, Sweden was hoping that by May, as many as 40 per cent of the residents of its capital Stockholm might have virus antibodies. In reality, perhaps only one-in-five residents actually do.
A study released this week in the UK’s Journal of the Royal Society of Medicine found it was likely infection levels in Stockholm were similar to those in London, despite Britain’s stricter lockdown. Yet, whatever route London and Stockholm took to get their current infection levels, it’s still higher than in many other places and that could be a benefit.
As much as 40 per cent of New Yorkers may have been infected with COVID-19 so may now be immune. Picture: Bryan R. Smith/AFPSource:AFP
CITIES WHERE HERD IMMUNITY MAY HAVE BEEN REACHED
While overall global immunity may be low, some reports have suggested there are pockets where it could be far higher.
Research from Britain’s University of Sussex has estimated around 13 per cent of Londoners could now have COVID-19 antibodies, 20 per cent of Spaniards and as many as 40 per cent of New Yorkers.
What all of these places have in common is they were struck hard, including suffering many deaths, by the virus in a first wave.
Also, right now at least, neither London or New York have been hit similarly hard by a second wave, if they’ve seen a wave at all. In fact, fewer than 1 per cent of tests in New York are currently coming back positive.
Sweden, too, is yet to a second wave. That’s not to say these cities won’t see another spike. In Madrid, heavily affected by coronavirus the first time around, that spike is indeed occurring.
In addition, infection levels could vary immensely across even one city. In New York, the presence of antibodies varies from 68 per cent in some neighbourhood to just 13 per cent in others.
New COVID-19 infections in London remain modest. Picture: Greater London Authority.Source:Supplied
The Sussex findings have not been peer reviewed. Some researchers, who concede the number of people infected in some areas is much higher than others, have questioned how great an effect that actually has anyway.
Antibody levels could still be low in those people who had only a mild case meaning the link between infection and immunity could be weaker than hoped. And the lack of an up tick in cases could be down to continued social distancing in cities hit hard by COVID-19 rather than herd immunity.
“While we would all like to believe that we are past the worst of this outbreak, the rising cases across many European countries would indicate that we are far from herd immunity and measures need to remain in force if we are to prevent a second wave even worse than the first,” Matt Keeling, a professor of disease at Britain’s University of Warwick told Newsweek.
LEVEL AT WHICH IMMUNITY MIGHT KICK IN
Professor Paul Franks and Professor Joacim Rocklov from Sweden’s Lund and Umea universities respectively, have said something other than just social distancing might be keeping a lid on a second wave in some areas.
“It is unlikely that lockdowns alone can explain the fact that infections have fallen in many regions after 20 per cent of a population has been infected.” they wrote in The Conversation.
The widely accepted view is if that 60 to 70 per cent of a population become infected, and produce effective antibodies, that should be enough to quell the disease’s spread.
However Profs Franks and Rocklov have speculated that some immunity can be achieved at an infection rate of a mere 20 per cent pointing to Sweden, New York and London’s relatively stable rates of new infections as some evidence of this.
Levels of herd immunity in Stockholm are not as high as the authorities imagined they would be. Picture: Jonathan Nackstrand/AFPSource:AFP
But, they added, if a 20 per cent threshold does exist it may not exist for everyone and the vulnerable may still be susceptible even as the fit and healthy brush off the virus.
And that’s one of the huge problems of attaining herd immunity naturally. How many people vulnerable to the disease’s worst effects die in the process? Can measures be put in place to protect them? Is it better to wait for a vaccine and social distance rather than aim for natural immunity that may not even be achievable?
“Understanding these complex interactions is going to be necessary if one is to meaningfully estimate when SARS-CoV-2 will burn itself out,” the authors of the Swedish paper said.
As with much of the pandemic, what strategies will emerge as the most effective is still far from clear.
No comments:
Post a Comment