In epidemiology as in most sciences, there is a prevailing conventional view and then there are other unconventional views.
In North America we are currently following the conventional view based on the research done by Neil Ferguson and his group at the Imperial College London, which I have referenced several times. According to this view, various social restrictions must be imposed to prevent the epidemic spread of Covid-19, with a primary aim to flatten the curve so that the health care system is not overwhelmed. The interpretation of where we are now, according to this view, is that as many locations in the US and Canada are opening too early, there will be another series of outbreaks that could reach epidemic proportions and will require another period of lockdown.
However, in the UK, there is a lively public debate about a number of other views. For some reason, the British media thinks its audience is intelligent enough to follow these scientific theories, whereas here in the “colonies”, we hear very little about them.
Sunetra Gupta and her group at the University of Oxford published research in March around the same time that the Imperial College of London released its report. In their view Covid-19 was circulating for quite some time before it was recognized as a pandemic. In the process, the Oxford research showed that many people had acquired immunity through these early unrecognized cases. Gupta argued that in fact the level of immunity was high enough to slow down the spread of Covid-19 without the extreme social measures and lockdowns imposed in the UK and other countries, and that the Imperial College model was an overreaction at an extremely high cost. https://unherd.com/2020/05/oxford-doubles-down-sunetra-gupta-interview/
Another theory being proposed by distinguished scientists Michael Levitt and Karl Friston, is that not all people are susceptible to Covid-19 because some have resistance. This may be due to past immune responses to other coronaviruses like the common cold. There is evidence that as much as 50% of the population has some of this resistance to Covid-19 at the T-cell level in the immune system. This means that Covid-19 will not spread as rapidly as when 100% of the population is susceptible, a typical assumption made with new viruses.
https://unherd.com/2020/06/karl-friston-up-to-80-not-even-susceptible-to-covid-19/
This video gives a good explanation of how this resistance may work in the immune system.
https://www.youtube.com/watch?v=fN3UmKSVCZ8&feature=youtu.be&t=133
While the UK research focuses on the UK and Europe, the same principles would apply to North America, just the numbers might be different.In our Covid-19 model for Canada, setting an initial immunity of 50% results in a rapid decline in cases that does not match actual case counts. With an initial immunity of 30%, we get a much slower increase in cases than when initial immunity is 0%, so that reimposition of lockdown is not needed until Dec 2021 instead of Sep 2020.
So if these contrary theories have merit, we may not see large outbreaks of Covid-19 in the ensuing months. In spite of increasing cases in a number of US states this week, it is too early to conclude that there will be epidemic outbreaks leading to a second wave requiring another period of lockdown.
