How long does it take to vaccinate the entire world?
If the each contaminated person transmits it to two other people, you'll need to keep half of the people immune to each at any single time. If you are doing this by vaccines, you'll need to give it to half of the people on that immunity window.
If the each contaminated person transmits it to two other people, you'll need to keep half of the people immune to each at any single time. If you are doing this by vaccines, you'll need to give it to half of the people on that immunity window.
And you must also syncronize it internationally.