5 ms·

The trial in question was conducted on younger people who generally don't get severe cases, so they have no evidence either way on that. However, the trial sho

The trial in question was conducted on younger people who generally don't get severe cases, so they have no evidence either way on that. However, the trial showed that that the vaccine appeared to nearly completely ineffective in preventing infection: > Nineteen of the 748 people in the group that was given the vaccine were infected with the new variant, compared with 20 out of 714 people in the group that was given a placebo. https://www.nytimes.com/live/2021/02/07/world/covid-19-coronavirus#south-africa-astrazeneca-vaccine https://www.nytimes.com/live/2021/02/07/world/covid-19-coron... The sample sizes here are small and the results have not been published, so it's too early to draw any major conclusions, but it certainly doesn't look great.

redis_mlc 6y ago
Those sample sizes are not small from a statistical standpoint. The interesting part of the article is that corona behavior varies that much. It calls into question quarantining while waiting for a vaccine - do we quarantine for the next decade?
giantDinosaur 6y ago
I wasn't aware that we thought any of the vaccines provide sterilising immunity. Has this changed? The Pfizer trial was regarded with some scepticism a while back as they didn't test everyone, so we don't really know how good it was at preventing infection, for example.
- garmaine 6y ago
  It appears that J&J does, and there is reason to be optimistic the Pfeizer and Moderna vaccines do, although the data isn’t in yet.
- pmg101 6y ago
  There was news last week that the AZ vaccine could reduce transmission by 76%. However although widely reported in the media I did see some controversy about this (as yet not peer reviewed) study. https://www.rte.ie/news/coronavirus/2021/0202/1194681-oxford-coronavirus-vaccine/ https://www.rte.ie/news/coronavirus/2021/0202/1194681-oxford...
oli5679 6y ago
A simple way to calculate Bayesian confidence intervals is sampling from Beta distributions. This is using the Beta(1,1) prior (uniform random) for both vaccine and control population. The data suggests it is unlikely that the vaccine reduces infection by >=50% (<5% probability) and a probability close to zero it reduces infection by >=70%. import numpy as np import pandas as pd # number of infections, and obs infect_ctrl,obs_ctrl=714, 20 infect_test, obs_test=748, 19 sample_C=np.random.beta(infect_ctrl+1, obs_ctrl-infect_ctrl+1, 100_000) # sample 100k times from posterior Beta distributions sample_T=np.random.beta(infect_test+1,obs_test-infect_test+1, 100_000) # percentage reduction in each sample perc_reduce = (val_C-val_T) /val_C # histogram of % reduction in infection pd.Series(perc_reduce).plot.hist(bins=20) # how likely, given this data, is > 50% reduction in infection from vaccine (perc_reduce >= 0.5).mean() # c. 3% (perc_reduce >= 0.7).mean() # <0.1%
swebs 6y ago
700 sounds like a pretty decent sample size to me.

redis_mlc 6y ago

Those sample sizes are not small from a statistical standpoint. The interesting part of the article is that corona behavior varies that much. It calls into question quarantining while waiting for a vaccine - do we quarantine for the next decade?

giantDinosaur 6y ago

I wasn't aware that we thought any of the vaccines provide sterilising immunity. Has this changed? The Pfizer trial was regarded with some scepticism a while back as they didn't test everyone, so we don't really know how good it was at preventing infection, for example.

garmaine 6y ago
It appears that J&J does, and there is reason to be optimistic the Pfeizer and Moderna vaccines do, although the data isn’t in yet.
pmg101 6y ago
There was news last week that the AZ vaccine could reduce transmission by 76%. However although widely reported in the media I did see some controversy about this (as yet not peer reviewed) study. https://www.rte.ie/news/coronavirus/2021/0202/1194681-oxford-coronavirus-vaccine/ https://www.rte.ie/news/coronavirus/2021/0202/1194681-oxford...

oli5679 6y ago

A simple way to calculate Bayesian confidence intervals is sampling from Beta distributions. This is using the Beta(1,1) prior (uniform random) for both vaccine and control population. The data suggests it is unlikely that the vaccine reduces infection by >=50% (<5% probability) and a probability close to zero it reduces infection by >=70%. import numpy as np import pandas as pd # number of infections, and obs infect_ctrl,obs_ctrl=714, 20 infect_test, obs_test=748, 19 sample_C=np.random.beta(infect_ctrl+1, obs_ctrl-infect_ctrl+1, 100_000) # sample 100k times from posterior Beta distributions sample_T=np.random.beta(infect_test+1,obs_test-infect_test+1, 100_000) # percentage reduction in each sample perc_reduce = (val_C-val_T) /val_C # histogram of % reduction in infection pd.Series(perc_reduce).plot.hist(bins=20) # how likely, given this data, is > 50% reduction in infection from vaccine (perc_reduce >= 0.5).mean() # c. 3% (perc_reduce >= 0.7).mean() # <0.1%

swebs 6y ago

700 sounds like a pretty decent sample size to me.