Infections in vaccinated Americans also may be as transmissible as those in unvaccinated people, the document said, and lead more often to severe illness.
The rate of spread of a virus follows a logistic curve. Those start off as exponential growth then slowly turn into exponential decay as they hit some max (everyone has had the virus, in this case). In virology, they call the base of the exponent at the start R₀.
Every math youtube channel and whatnot did this bit at the start of the pandemic. Being already familiar with exponential stuff, I assumed R₀ was somewhere in the 1-2 range. You know, because a huge compound interest rate is 1.1. Or in computer science, a base 2 exponent means something is either impossible or free. I didn't look up the actual numbers for months.
Anyway, it turns out that R₀ values for viruses are fucking wild and I was hella wrong about it being in the 1-2 range.
R0 is the average amount of people a person infected with an illness will pass it on to/transmit too. It's exponential by nature. Original Covid strain had an R0 between 3 and 4, Covid delta has an to R0 between 5 and 9. Chicken pox has an R0 around 10. I'm just going to illustrate an example comparing an R0 of 3 Vs one of 6, imagine this is the difference between Covid original and Covid delta.
Example of an R0 of 3 (Original Covid)
1 person infects 3 people. Now 4 people have the the virus. Now those three people infect three people each (3x3). Now 13 people have the virus. Now those 9 new hosts infect 3 people each. (9x3) Now 40 people have the virus. Now those 27 new hosts infect 3 people each (27x3). Now 121 people have the virus. Now those 81 new hosts infect 3 people each (81x3). Now 324 people have the virus. Etc, etc etc
Example of an R0 of 6. (Delta variant)
1 person infects 6 people. Now 7 people have the virus. The 6 new hosts infect 6 people each. (6x6). Now 41 people have the virus. The 36 new hosts infect 6 people each. (36x6). Now 257 people have the virus. Now those 216 hew hosts infect 6 people each (216x6). Now 1512 people have the virus. Now those 1296 new hosts infect 6 people each (1296x6). Now 9288 people have the virus.
So just a doubling of the R0 from around 3 to around 6 increases infectivity of the virus 28 times, as R0 is exponential by nature.
It means that if you dropped the average person with Covid Classic into a completely unexposed, unvaccinated population, they'd infect 4 people, but if they had Covid Delta they'd infect 6.
No difference between two numbers is exponential. 2 → 4 → 6 → 8 → 10 is linear. 2 → 4 → 8 → 16 → 32 is exponential. 2 → 4 is nothing.
The rate of spread of a virus follows a logistic curve. Those start off as exponential growth then slowly turn into exponential decay as they hit some max (everyone has had the virus, in this case). In virology, they call the base of the exponent at the start R₀.
Every math youtube channel and whatnot did this bit at the start of the pandemic. Being already familiar with exponential stuff, I assumed R₀ was somewhere in the 1-2 range. You know, because a huge compound interest rate is 1.1. Or in computer science, a base 2 exponent means something is either impossible or free. I didn't look up the actual numbers for months.
Anyway, it turns out that R₀ values for viruses are fucking wild and I was hella wrong about it being in the 1-2 range.
I know some of these words
R0 is the average amount of people a person infected with an illness will pass it on to/transmit too. It's exponential by nature. Original Covid strain had an R0 between 3 and 4, Covid delta has an to R0 between 5 and 9. Chicken pox has an R0 around 10. I'm just going to illustrate an example comparing an R0 of 3 Vs one of 6, imagine this is the difference between Covid original and Covid delta.
Example of an R0 of 3 (Original Covid)
1 person infects 3 people. Now 4 people have the the virus. Now those three people infect three people each (3x3). Now 13 people have the virus. Now those 9 new hosts infect 3 people each. (9x3) Now 40 people have the virus. Now those 27 new hosts infect 3 people each (27x3). Now 121 people have the virus. Now those 81 new hosts infect 3 people each (81x3). Now 324 people have the virus. Etc, etc etc
Example of an R0 of 6. (Delta variant)
1 person infects 6 people. Now 7 people have the virus. The 6 new hosts infect 6 people each. (6x6). Now 41 people have the virus. The 36 new hosts infect 6 people each. (36x6). Now 257 people have the virus. Now those 216 hew hosts infect 6 people each (216x6). Now 1512 people have the virus. Now those 1296 new hosts infect 6 people each (1296x6). Now 9288 people have the virus.
So just a doubling of the R0 from around 3 to around 6 increases infectivity of the virus 28 times, as R0 is exponential by nature.
So if COVID classic is at a 4, and Delta is at 6... that's a 50% increase? So it's more, but not exponentially more?
It means that if you dropped the average person with Covid Classic into a completely unexposed, unvaccinated population, they'd infect 4 people, but if they had Covid Delta they'd infect 6.
No difference between two numbers is exponential. 2 → 4 → 6 → 8 → 10 is linear. 2 → 4 → 8 → 16 → 32 is exponential. 2 → 4 is nothing.
Problem is they're estimating the R0 of Covid delta between 5 and 9, which is uhh very not good if it turns out to be closer to the upper bound
R0 isn't some stable thing, contrary to popular belief. It is influenced by how people behave and environmental factors.
True but the behaviour of your average American is not a positive in this case either.
Yeah that's why I said that, to explain why in some places it may be higher
It's exponentially more unfortunately. R0 is exponential by nature
Ah I read your other comment and now I get it.
Here's the graph from the CDC comparing diseases. Covid delta is almost a new illness in terms of transmission
https://pbs.twimg.com/media/E7hKcosVIAQr_a9?format=jpg&name=large