The government now tells us “hands, face, space, fresh air”* to reduce transmission of COVID-19, but the evidence supporting these four measures is very weak. By contrast the evidence showing that the Oxford AstraZeneca vaccine I had a few weeks ago is safe, is much much stronger, and assessed much more rigorously.
Let’s take them in order:
- “Hands”: There is essentially no good evidence that washing hands and surfaces reduces the likelihood of catching COVID-19.
- “Face”: by which they mean masks. We understand fairly well how mask work, colleagues at Bristol have a paper recently out in Physics of Fluids, and this is just a small part of a lot of work over the past year, that has assessed how effective masks (of different types) are. So we have a reasonable idea of how effective a given type of mask is at filtering out virus-containing droplets of a given size, but unfortunately, we have little idea of what size of droplet are transmitting COVID-19. Vaccines like those for COVID-19 are typically tested via a randomised controlled trial (RCT), we have almost no RCT data here.
- “Space”: by which they mean 1 or 2 m “social distancing”. As you can tell by the various limits of 1 m, 2 m, 6 feet, etc suggested by different countries there is no well justified distance beyond which you are safer. But basic geometry tells you that the concentration of virus will be highest right in front of an infected person, in their breath, so there is sound logic behind not getting too close, especially if you are facing someone. No RCT data here either.
- “Fresh air”: There a observations of “superspreader” events in which multiple people are infected, and they are strongly associated with people being together indoors, and in rooms with poor ventilation, i.e., air that is the opposite of fresh. We also have a reasonable understanding of the mechanism, and a simple model (Wells-Riley model).
In summary, superspreading events give pretty strong direct evidence that sharing a poorly ventilated room with an infected person is a recipe for becoming infected. As the virus is breathed out by an infected person, them common sense and basic geometry tells you that being within a metre or two of an infected person. especially talking directly to them, is more dangerous than being farther away. However, I am not aware of any direct study of this.
Apart from that we are rather guessing as to how COVID-19 is transmitted. The reason for our lack of understanding is that there is very little research into what the mechanism of COVID-19 transmission actually is. Part of this that research into infectious diseases has long been the poor cousin of research into cancer. That explains why in early in the pandemic we knew little of how COVID-19 is transmitted.
But this post is written in June 2021, when there is still very little research into how COVID-19 is transmitted, despite over a 100 million cases and over 3 million deaths. There has been no large scale research into transmission despite not only the millions of deaths but also trillions in economic damage. You would have thought that spending, say, a billion on research would be money well spent if a better understanding of how COVID-19 spreads could be used to improve how we socially distance or better balance measures to reduce transmission with keeping, for example, the hospitality sector going. But apparently not many (influential) people reason this way.
One person who maybe thinks this way (now if perhaps not for as long as he would have us believe?) is Dominic Cummings. He name checks General Groves – the director of the Manhattan project that developed atomic bombs. In the second world war, the American government under President Franklin Roosevelt brought together one of the greatest collections of scientific talent ever assembled, to address the huge urgent scientific and engineering challenge of developing the atom bomb before Nazi Germany could.
The challenge of figuring out how people become infected with COVID-19 has not, to put it mildly, attracted the same effort. There has been a huge and very successful effort to develop vaccines, which I am truly thankful for. But the vaccines have been a lone scientific success. Although many scientists and medics (eg in the World Health Organisation) have contributed to the lack of progress in understanding how COVID-19 spreads, it is also true, I think, that in governments we need more people like Groves and Roosevelt and less like Trump and Harding.
* It was just “hands, face, space” until recently, “fresh air” has been added recently. Given the evidence for transmission being predominantly indoors often in poorly ventilated rooms, the addition of “fresh air” is an improvement.