Modelling has it's drawbacks, BUT, multiple runs were made of varying scenarios supported by a professor of Mathematics from a different University who made calculations that support the theory. Their paper can be found here
Abstract
It is widely believed that the herd immunity threshold (HIT) required to prevent a resurgence of SARS-CoV-2 is in excess of 50% for any epidemiological setting. Here, we demonstrate that HIT may be greatly reduced if a fraction of the population is unable to transmit the virus due to innate resistance or cross-protection from exposure to seasonal coronaviruses. The drop in HIT is proportional to the fraction of the population resistant only when that fraction is effectively segregated from the general population; however, when mixing is random, the drop in HIT is more precipitous. Significant reductions in expected mortality can also be observed in settings where a fraction of the population is resistant to infection. These results help to explain the large degree of regional variation observed in seroprevalence and cumulative deaths and suggest that sufficient herd-immunity may already be in place to substantially mitigate a potential second wave.
Modelling suggests threshold needed to prevent resurgence may be as low as 20 per cent
The researchers posit that some of the population may already have a high level of immunity to Covid-19 without ever having caught it.In a paper yet to be peer-reviewed, they point to evidence suggesting exposure to seasonal coronaviruses, such as the common cold, may have already provided some with a degree of immunity, and note that others may be more naturally resistant to infection.Modelling how differing levels of pre-existing immunity between individuals could affect the overall “threshold” needed to prevent a resurgence of the virus, they found that this could be as low as 20 per cent.
“It is widely believed that the herd immunity threshold (HIT) required to prevent a resurgence of SARS-CoV-2 is in excess of 50 per cent for any epidemiological setting,” wrote Jose Lourenco, Francesco Pinotti, Craig Thompson, and Sunetra Gupta, all of Oxford University.
“Here, we demonstrate that HIT may be greatly reduced if a fraction of the population is unable to transmit the virus due to innate resistance or cross-protection from exposure to seasonal coronaviruses.”
They added: “These results help to explain the large degree of regional variation observed in seroprevalence and cumulative deaths and suggest that sufficient herd immunity may already be in place to substantially mitigate a potential second wave.”
Calculations along a similar line by Gabriela Gomes, a professor of mathematics and statistics at Strathclyde University, have also placed the threshold needed for herd immunity at below 20 per cent.
For diseases where a vaccine is available, herd immunity is often calculated with the assumption that everybody has the same level of immunity – known as a homogenous model.
But, as with the Oxford researchers, Dr Gomes has been studying what are known as heterogeneous models – which operate on the basis that there are vastly differing levels of immunity within the population.
The two models can have vastly different results. “There doesn’t need to be a lot of variation in a population for epidemics to slow down quite drastically,” Dr Gomes told The Atlantic this week.“The outbreaks look similar at the beginning. But in the heterogeneous population, individuals are not infected at random.“The highly susceptible people are more likely to get infected first. As a result, the average susceptibility gets lower and lower over time.”She added: “We just keep running the models, and it keeps coming back at less than 20 percent. It’s very striking.”
The concept of herd immunity, previously an esoteric term (SPECIALIZED) largely consigned to the realm of epidemiologists, became politicised in the UK after Boris Johnson revealed that Downing Street had considered letting the country take the brunt of the virus “on the chin” rather than introduce strict lockdown measures.
Lots of people will associate "esoteric" with spiritual, magical or secret societies- because most people won't bother themselves with word defintions!Esoteric: intended for or likely to be understood by only a small number of people with a specialized knowledge or interest.Specialized would have been a better word choice for the illiterates out there.. Or maybe even that's a bit much?
Specialized : working in and knowing a lot about one particular subject, skill, service, etc. :