The word ‘efficacy’ is very old. It dates back to the 1200’s! It didn’t enter my consciousness until this year, when the term was used in relation to COVID-19 vaccines.
A vaccine with an efficacy rate of, say 85%, means it demonstrated in trials that it could reduce moderate to severe disease by 85%. To do that, the vaccines initiated an immune response that reduced the number of viruses in the lower respiratory tract. To date, the vaccines are not believed to be sterilizing vaccines that completely stop the virus in the upper respiratory tract too.
In time, the vaccine may prove to be a sterilizing vaccine in some or most of the population. Until then, some governments, such as the one in my province, explain the vaccine in terms of effectiveness in preventing severe disease, hospitalizations and death from COVID-19′.
Here is an excellent explanation of the Covid Vaccine: University of Colorado.
What about Mask Efficacy?
I somehow doubt there will be a mask efficacy rating for the products used by the general public during Covid. There are simply too many variables – material, fit, care in use; indoors vs outdoors; social distancing and other factors limiting people’s activities; age, immunity, viral load and length of exposure of participants… Analyzing masking is going to be either a statisticians dream or nightmare.
In preparation for the (hopefully) soon removal of mask mandates, last week I performed a small test on public perception of an unmasked person (me). I had to drop a sample off at a medical lab. I walked two car lengths across a parking lot, stood in an outside lineup of one (me) for about two minutes then handed the sample (while still outside) to the masked attendant who, by protocol, stepped outside to receive it.
While I was being a line of one, there was, for a few seconds, a lineup of two – another ‘client’ arrived. Unlike me, she was masked. When the attendant moved to the door to summons me, the masked lady behind me swiftly moved forward to try to hand her item to the attendant. As she came up beside me, she suddenly drew back. I don’t know whether it was because she saw I was unmasked or whether she realized that I was handing a sample to the attendant too.
Either way, I didn’t learn anything about public perception because the attendant and the client were masked – I couldn’t read anything in their faces.
Efficacy of the Virus
Efficacy isn’t actually the term used to describe Covid mortality – it is called Case fatality. In both Canada and the USA it is 1.8%. There are, however, an unknown number of people who have had Covid, but were not diagnosed with it, which drops the case fatality rate by some unknown amount. The fatality rate in terms of the entire population are .07% for Canada and .18% for the United States.
I’m hoping we aren’t invaded by a new and more deadly variant so that our province can move towards full removal of restrictions by the end of June… inshallah…