Read on Twitter
Lots of folk already commented on “1 or 2 dose”. One thing that comes up often is “efficacy”, followed by numbers like “80%”, 95%”. In many cases, it reads as if folk think this is how much YOUR chance of getting the virus is reduced by. That’s incorrect.
These figures are actually the relative risk reduction (RRR) of infection with the vaccine. Eg. 2000 people without Covid-19 - 1000 vaccinated (group 1), 1000 not vaccinated (group 2).
200 people (20%) in group 2 get Covid-19
10 people (1%) in group 1 get Covid-19
= 95% RRR
200 people (20%) in group 2 get Covid-19
10 people (1%) in group 1 get Covid-19
= 95% RRR
The absolute effect is 19% (difference between 1% and 19%).
Another way of putting it = in 1000 people who don’t have Covid and are not vaccinated, 200 will catch it.
If the same 1000 people had the vaccine, 10 would get it, meaning 190 will be spared.
Another way of putting it = in 1000 people who don’t have Covid and are not vaccinated, 200 will catch it.
If the same 1000 people had the vaccine, 10 would get it, meaning 190 will be spared.
But, we also have to say “we do not know if you will be one of those 190 people spared or one of the 10 who still get it.” “We also don’t know if you will be one of the 800 who won’t get the disease/virus with or without vaccine”.
Understanding this is important, not least as we will see in the coming months headlines of people who have been vaccinated still catching Covid. This should be a surprise to no one. I’ve just shown you why.
2nd - vaccination shifts the needle to fewer infections in the population. Remember this. It’s not YOUR risk per se, but risk in the population that is reduced. If you want things to go back to normal, vaccines are one of our most effective, safest & speediest ways to get there.
A note on the above - I have a single point estimates throughout (eg. 95% relative risk reduction, 19% [1 in 5] absolute risk reduction). This implies certainty/no error around these numbers which is not the case. There will be a range for these efficacy data eg 85% to 99% RRR
If that error surprises you then you should know that all science has error, medical research included
What should encourage you is for the Covid-19 vaccines, the error around the efficacy data is the most accurate account of it we can get because of the type of research done
What should encourage you is for the Covid-19 vaccines, the error around the efficacy data is the most accurate account of it we can get because of the type of research done
The studies performed were randomised controlled trials (RCTs). When done well, these provide is with the most accurate data on efficacy of a treatment AND the error around these data.
The Covid-19 RCTs were done very well. We can trust their data (and the error around these)
The Covid-19 RCTs were done very well. We can trust their data (and the error around these)
Useful responses to this thread
@AnnOssinger makes important point about severity of disease if you have vaccine & still get Covid
Data on this are actually quite sparse, but of what we do have points in this direction (screenshot from @hildabast blog https://absolutelymaybe.plos.org/2020/12/20/why-two-vaccines-passed-the-finishing-line-in-a-year-and-others-didnt-and-a-month-12-roundup/) https://twitter.com/annossinger/status/1345489309177053185
@AnnOssinger makes important point about severity of disease if you have vaccine & still get Covid
Data on this are actually quite sparse, but of what we do have points in this direction (screenshot from @hildabast blog https://absolutelymaybe.plos.org/2020/12/20/why-two-vaccines-passed-the-finishing-line-in-a-year-and-others-didnt-and-a-month-12-roundup/) https://twitter.com/annossinger/status/1345489309177053185
@Rooftopvegplot raises similar point around severity of disease with vaccine, and also risk of death.
As far as I’m aware, death wasn’t an outcome measure in any of the trials (too short follow up). As such, I believe there were no recoded deaths in any arms of the RCTs to date https://twitter.com/rooftopvegplot/status/1345644659780055047
As far as I’m aware, death wasn’t an outcome measure in any of the trials (too short follow up). As such, I believe there were no recoded deaths in any arms of the RCTs to date https://twitter.com/rooftopvegplot/status/1345644659780055047
