The thing is, at some point it does mean the virus is unstoppable, in the sense that no reasonable or worthwhile attempt to stop it has any chance of success, outside of at most protecting particular vulnerable groups and doing mitigation. If the baseline transmission is higher than Delta and it’s mostly ignoring vaccinations, what is your plan exactly? Lock down much harder than we did in 2020? Close the grocery stores?
Naïve calculation: if surgical masks blocked 75% of aerosols going out and coming in, and if all transmission were through aerosols, and if people wore these masks all the time, this could theoretically overcome R0 = 16 (because the transmission would be reduced a factor of four in both steps). Of course it will not work out this well, but then there are many other measures that can be taken in addition. So I think it would be technically feasible to keep it under control. But if it were to run quickly through most of the population, omicron would have to be much less severe than other variants to not overwhelm hospitals (without massive scale up of treatments).
Masks work by reducing the fraction of virus particles from an infected individual that get into the air, or the fraction in the air that get into the wearer. My understanding is that this isn’t a direct multiplier on R0, it’s a multiplier on how long (on average) you need to be around an infected person, or a concentration of aerosolized virus particles, before you’ve accumulated enough exposure to become infected yourself. Unmasked, with no immunity, the relevant exposure times (as measured early in the pandemic) were on the order of 15 minutes. Good masks for both parties would get you into the range of a few hours. Not sure how that changes with the newer and more infectious strains, but I assume the times are shorter. But basically, my take has been that if you’re going to be around someone for more than a few hours (like your coworkers or classmates), then unless you’re wearing N95 masks near-perfectly, it’s unlikely they’re going to accomplish much. Not literally nothing, but much less than they do for brief encounters.
It’s hard to pin down a threshold of a specific time of exposure because it depends on the minimum infectious dose, which varies widely among people, at least for lots of diseases. Also, the rate of shedding varies widely based on the progression of the disease, whether the person is talking, how far away the person is, etc. Furthermore, the HVAC system causes additional variation. So I think when you add all these uncertainties, a 16 times reduction in emission/inhalation would correspond to very roughly a 16 times reduction in infection, but I would be very interested to see if someone has run the math on this.
Great work!
Naïve calculation: if surgical masks blocked 75% of aerosols going out and coming in, and if all transmission were through aerosols, and if people wore these masks all the time, this could theoretically overcome R0 = 16 (because the transmission would be reduced a factor of four in both steps). Of course it will not work out this well, but then there are many other measures that can be taken in addition. So I think it would be technically feasible to keep it under control. But if it were to run quickly through most of the population, omicron would have to be much less severe than other variants to not overwhelm hospitals (without massive scale up of treatments).
Masks work by reducing the fraction of virus particles from an infected individual that get into the air, or the fraction in the air that get into the wearer. My understanding is that this isn’t a direct multiplier on R0, it’s a multiplier on how long (on average) you need to be around an infected person, or a concentration of aerosolized virus particles, before you’ve accumulated enough exposure to become infected yourself. Unmasked, with no immunity, the relevant exposure times (as measured early in the pandemic) were on the order of 15 minutes. Good masks for both parties would get you into the range of a few hours. Not sure how that changes with the newer and more infectious strains, but I assume the times are shorter. But basically, my take has been that if you’re going to be around someone for more than a few hours (like your coworkers or classmates), then unless you’re wearing N95 masks near-perfectly, it’s unlikely they’re going to accomplish much. Not literally nothing, but much less than they do for brief encounters.
It’s hard to pin down a threshold of a specific time of exposure because it depends on the minimum infectious dose, which varies widely among people, at least for lots of diseases. Also, the rate of shedding varies widely based on the progression of the disease, whether the person is talking, how far away the person is, etc. Furthermore, the HVAC system causes additional variation. So I think when you add all these uncertainties, a 16 times reduction in emission/inhalation would correspond to very roughly a 16 times reduction in infection, but I would be very interested to see if someone has run the math on this.