ARE WE ALREADY IMMUNE TO CORONAVIRUS?

KT NEWS SERVICE. Dated: 9/5/2020 4:24:13 PM

NEW DELHI, Sep 4: Why so much worry about the dreaded virus killing people across the world? Prof. Sunetra Gupta, a professor of theoretical epidemiology, points out her recent study on the herd immunity threshold, as well as her views on the social costs of lockdown, the inaccuracy of epidemiological models, and the curtailment of academic debate.
A study produced by her team at Oxford University indicates that some parts of the United Kingdom may already have reached herd immunity from coronavirus. A significant fraction of the population, according to the study published last week, may have "innate resistance or cross-protection from exposure to seasonal coronaviruses," making the proportion vulnerable to coronavirus infection much smaller than previously thought.
Dr Sunetra Gupta says the cost of lockdown will be too high for the poorest in society and questions the language and quality of debate on the pandemic’s impact. Excepts from her interview in British journal Reaction.
The principle of protection from exposure to related viruses, and indeed any kind of pathogen, is one that we’ve known for a very long time. The very first vaccine we had, which is smallpox, was based on the idea that cowpox protects against smallpox. This idea was already there well in advance of us knowing that smallpox was a virus – and indeed in advance of germ theory having been properly established. So we knew about this cross protection even before we knew that diseases were caused by germs. It’s a very old idea.
In my own studies, beginning with malaria and then later thinking about flu, the role of cross-immunity in protecting against disease seemed to be something that very much needed to be factored into our thinking. Most of the people who die from malaria are children, and they die upon their first exposure, because they have no immunity at that stage. That was one of the first things that struck me when I was working on malaria.
And then later when I was working on flu, it seemed to me a very good way of explaining why the 1918 flu had killed so many people, but why that didn’t seem to be repeating itself, was that it was likely that people hadn’t been exposed to flu. Many people would have not had the flu at all. So then that built up this population of naive immunity in people under the age of thirty who were very badly affected when the pandemic came through.
Having those ideas in mind, when the Covid-19 virus started to spread, I was pretty certain it wouldn’t have a huge, devastating impact in terms of mortality, because we had all these other coronaviruses circulating.
What I didn’t anticipate was that some of our responses to previous exposure to seasonal coronaviruses might actually protect us from infection. It’s one thing to get infected and not ill, but what the new studies are showing is that people are actually fighting off infection. So at an even more basic level, the pre-existing antibodies or T-cell responses against coronaviruses seem to protect against infection, not just the outcome of infection.
What we know is that the seropositivity rates in many parts of the world are much lower than we’d expect them to be if we assume that the epidemic has passed through and that people are resistant. If you take a very simple scenario where everyone is susceptible, you’d expect 60-70% of them to have some marker of exposure. And that is not what’s been observed.
The fifth piece of this jigsaw of the virus could be that there is some seasonality. I suspect that in the winter it will probably come back, but hopefully only to the regions where it was kept from going by lockdown, and where the seroprevalence levels are genuinely extremely low.
I mean, there are areas where it is very high. There’s a paper published recently of a seroprevalence study done in the slums of Buenos Aires, which reports a 50% seroprevalence. And there have been studies from Lodi, Italy, where it is I think 60%.
So there are studies on the high side, but I think one can’t really trust studies on either side completely. One has to take all these measures with a certain degree of caution. What we have here are a range of measures. In cities, it’s typically much higher than in rural areas or areas that are non-urban.
One of the things that’s been done in reporting the seroprevalence, which is not correct, is that they’ve been homogenised. When people say only 5-6% of the UK population has been exposed, that’s not correct. I think very few people would agree that exposure rates in London are less than 20%.
There’s the herd immunity threshold, which is the point at which enough people are immune to a pathogen that the rate of growth will start to decline. But there will still be more cases. Typically in an epidemic, we overshoot that threshold. So if you see an area that has a seroprevalence with 60%, that doesn’t mean that herd immunity can’t be much lower than that. What that threshold does define for us is how many people in the community you need to be immune for that thing not to take off.
On the talk of international travel as a disease vector and that we will never get back to normal, I think the trade-off is very extreme. Obviously the most extreme manifestation of that trade-off is the 23 million people who will be pushed below the poverty line as a result of this sledgehammer approach. The costs to the arts is I think also incredibly profound – the theatres and all other forms of performing art. But also the inherent art of living, which I think is being compromised.
Acts of kindness are being eschewed. Someone was telling me yesterday that their mother said to them “please don’t come home, you’re going to kill us”.
What politicians can do is maybe alter their language to reflect that we do live with risk, we have to make quite difficult decisions about trade-offs that exist between ways of life, between livelihoods, and sacrifices that have to be made at a societal level. They would do well to urge people to think at a communitarian level.
I think the lockdown is really individualistic in its general construction. Things that we normally disperse within the community, such as individual risk, and individual blame. Now I see young people being terrified, even though they realise the risk to themselves is low, that they might infect a friend who will then give it to their grandparents. This chain of guilt is somehow located to the individual rather than being distributed and shared.

 

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