When the virus is circulating in a vaccinated population, variants that are more rapidly transmitting are selected for --- those are vaccine evading variants.
By vaccinating without shutting down transmission we are promoting vaccine evading variants.
By vaccinating without shutting down transmission we are promoting vaccine evading variants.
For those who want to take a look at the math of evolution, take a look at my textbook, Chapter 6. Downloadable from
necsi.edu/dynamics-of-co…
necsi.edu/dynamics-of-co…
Mass vaccination in a population causes a bias in the fitness landscape---the fitness of each of the variants is different. Those that are vaccine evading have a fitness advantage, i.e. replicate faster than those that don't.
When we suppress transmission (masks, social distancing, no gatherings), we reduce fitness of variants. Fitness and R are related. If R<1 they just disappear over a short time.
When we allow transmission, vaccine evading variants grow in number and dominate over time.
When we allow transmission, vaccine evading variants grow in number and dominate over time.
When vaccines suppress transmission they also reduce the fitness of variants--the main point of vaccinating. But they suppress especially those they are targeting.
This is their strength and weakness. If we don't shut down transmission with whatever means we can (including both vaccines and masking, social distancing, not gathering), the virus mutates to bypass the vaccines and we are left with only the other ways of fighting the virus.
In the meantime, while this is happening, the virus also is mutating to be more transnmissible overall. So the virus is worse and we lost the help of the vaccine.
This is what has happened over the past year. We have a worse virus and vaccines that are weaker.
This is what has happened over the past year. We have a worse virus and vaccines that are weaker.
The current efficacy of the vaccines against the Delta variant leads to roughly 2-3 reduction of transmission, but the Delta variant is 2-3 times more transmissible.
The prevention of severe cases is about 2-3 and the Delta is about 2-3 more severe.
The prevention of severe cases is about 2-3 and the Delta is about 2-3 more severe.
This means that while we gain from vaccination today and therefore should vaccinate, overall since a year ago we have not gained much, if any, ground in the fight against the virus.
Where we have lost is in the reduction of use of mesures to prevent transmission. So that makes the danger for everyone worse.
Children and unvaccinated people are more severely affected, are not vaccinated, and many more are going to school, so they are getting the worst of it.
Children and unvaccinated people are more severely affected, are not vaccinated, and many more are going to school, so they are getting the worst of it.
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