Up to now, Covid hasn't been lethal enough or common enough for 100% of people to want to be vaccinated.

It takes multiple people among one's friends and family dropping like flies to convince people in vaccine-hesitant places with ample supply (e.g. Bulgaria) to chose to get vaccinated.

Also it wouldn't hurt if vaccines were actually effective at preventing infection (rather than allowing infection but preventing severe disease)... and if they lasted more than half a year.

The vaccines last more than half a year. Certain nice-to-have bonus effects beyond "you probably won't die or suffer long-term effects and you're less likely to spread it" fade a bit after six months. The booster is for the nice-to-haves, like reducing symptomatic but minor-moderate infections.

Every single benefit of the vaccines seem to fade over six months or so - not justt symptomatic infections, but also protection against serious effects, hospitalization, and death. That's why there's been so much push for boosters even in countries like the UK which have given up on stopping the spread of the virus. (Yes, I know the WHO is opposed to booster shots, but frankly they seem to be a bunch of idiots who care more about what's politically useful than reality these days.)

Don't forget that animals also get and transmit covid.

Massive difference between 4 billion and 1 billion. We are already at 4 billion now. Also, some countries are hitting 90%.

If a large portion of the population is vaxxed, it stops spreading as much even among the unvaxxed, which reduces opportunity to mutate.

Deer don't have the same selective pressure as we do.

Is there any actual evidence of decreased spread because of the vaccine? I was under the impression that it simply changed the intensity of the disease.

Yes, the evidence is there - it is less likely to transmit and less likely to be caught. Most of this evidence comes from testing of contacts because unfortunately there are pretty large confounding effects around likelihood to get tested based on severity of illness.

Also, the vaccine has been shown to reduce viral load which has an impact on rate of mutation even if you are infected.

> the vaccine has been shown to reduce viral load which has an impact on rate of mutation even if you are infected.

This doesn't seem to be the case⁰:

A new study from the University of California, Davis, Genome Center, UC San Francisco and the Chan Zuckerberg Biohub shows no significant difference in viral load between vaccinated and unvaccinated people who tested positive for the delta variant of SARS-CoV-2. It also found no significant difference between infected people with or without symptoms.

When they analyzed the data, the researchers found wide variations in viral load within both vaccinated and unvaccinated groups, but not between them. There was no significant difference in viral load between vaccinated and unvaccinated, or between asymptomatic and symptomatic groups.

⓪ - https://www.ucdavis.edu/health/covid-19/news/viral-loads-sim... (Link to study in the article)

The evidence is mixed https://www.nature.com/articles/s41591-021-01575-4

On a viruses mutation potential? 1bn and 4bn is not orders of magnitude different. I don't think 1bn unvaccinated people is a guarantee of no more mutations. Especially when the vaccinated are still spreading, and selecting for more infectious mutations also.

Nothing is a guarantee of no mutations, that is why we think of the world probabilistically.

But there is a multiplicative effect - the sparser unvaxxed people become, the less general spread there will be.

The vaxxed are still spreading and it is true they cause selection, but this has been well studied and widespread vaccination absolutely would help reduce the rate of mutation.

> [...] this has been well studied and widespread vaccination absolutely would help reduce the rate of mutation.

I don't understand how this could be. Studies have shown that peak viral load is the same for vaccinated/unvaccinated, that means roughly the same number of replicative cycles in vaccinated as in unvaccinated. Each replication is a chance for the virus to aquire mutations, so same number of replicative cycles in vaccinated/unvaccinated means same rate of mutation in vaccinated/unvaccinated.

The science is not at all set on whether peak viral load is the same or not. Most of it seems to suggest that it is not the same initially, but might revert to it after 6-9 months after being vaxxed.

Spread is also less common among the vaxxed as I said, so even if it turns out to be no difference in load, there is still less opportunity for selection.

https://twitter.com/trvrb/status/1462816243245719558?t=9OCuB...

> even if it turns out to be no difference in load, there is still less opportunity for selection.

How so? Load means number of virus particles. Number of virus particles increases with the number of replication cycles. The probability of mutation increases with the number of replications. So, same number of replication cycles, (roughly) same chance of mutation.

Due to difference in rate of infection, both by spread and risk of contraction. Your UC Davis article does not show otherwise (it is conditioning on aspects of the infection among those already infected and does not measure the risk of being infected - only percent of days you test PCR positive), and there is extensive evidence showing less risk of both among the vaccinated.

https://www.cdc.gov/coronavirus/2019-ncov/science/science-br...

https://jamanetwork.com/journals/jama/fullarticle/2786040

The science around viral dynamics re: viral loads is much more uncertain than this - so I am not saying it is definite that the viral loads are less, only that there is both a mechanism and some evidence to suggest it is either less or quicker to go down (but the evidence here is mixed and it likely wears off).

But nonetheless, the science on transmissibility - even with breakthrough, is more certain.

You seem to be spreading misinformation all over this thread.

Here[0]'s a study from Nov 19th, saying that:

No significant differences were detected in duration of RT-PCR positivity among fully vaccinated participants (median: 13 days) versus those not fully vaccinated (median: 13 days; p=0.50), or in duration of culture positivity (medians: 5 days and 5 days; p=0.29).

[0] - https://www.medrxiv.org/content/10.1101/2021.11.12.21265796v...

Please provide some citations to back up your claims.

Nothing I said has anything to do with duration of positivity?

A few citations on why the evidence leans towards reducing the spread being more effective at reducing variant selection: https://twitter.com/trvrb/status/1462816243245719558?t=9OCuB... Here is a citation regarding viral load. https://www.nature.com/articles/s41591-021-01575-4

Quote from the study you linked: "[...] we found that BTIs[breakthrough infections] in recently fully vaccinated individuals have lower viral loads than infections in unvaccinated individuals. However, this effect starts to decline 2 months after vaccination and ultimately vanishes 6 months or longer after vaccination."

Superbug, anyone?