A tiny number of virus organisms placed in the back of a person’s throat one time is not likely to lead to the average person getting “sick” with COVID. If we placed a tiny number of live viruses in the throats of 1,000 people, less than half would probably get sick. If we placed 1,000 or 1,000,000 viral organisms, the average person probably would get sick. And if we placed a tiny number of organisms 10 or 100 times in a week, the average person would also likely get sick because of the multiple exposures. This is because even in your throat, your body has protective countermeasures such as mucus and cilia and your blood and other fluids likewise have generic immune and other protections. They are just not as strong as we need them to be. Even as people get and recover from COVID or get a future vaccine, 100% of the population won't be 100% protected, but collectively we will be safe.
Your nose reduces the risk of viral particles getting to your throat. A mask reduces the risk of the viral particles getting to your nose, and social distancing reduces the risk of them getting to your mask. Together, these countermeasures work very well. If your nose reduces the risk by 80% (see Caveat 1), and a mask by another 80% and the six foot distance by 80% more, then collectively, the failure rate would be (0.2*0.2*0.2 = .008) = 0.8%. In other words, the collection of countermeasures would be (1 minus the failure rate) = over 99% effective in reducing your chances of getting sick. In this example, any two together would be 96% effective and any one alone would be 80% effective.
So based on this example calculation, if you are standing with your mouth closed and normally breathing close to a COVID carrier as they are speaking to you, you may have a 20% chance of getting sick from that exposure. Add a mask and that would go down to 4%, add distance and that goes to under 1%. Add repeated individual exposures from other people, and your risk gets worse. Add more countermeasures and your safety improves. The power of each individual countermeasure is much less important than their collective power in protecting you.
Much more here:
https://www.linkedin.com/content-guest/article/saving-your-health-one-mask-time-peter-tippett-md-phd
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