Well if the vaccines only stop spread by 50 per cent, how are they the way out of all this?
‘Spread’ is not that simple.
From the data we have so far, we know that vaccines stop you getting infected by well over 50%. It varies by vaccine and the data I is emerging still but Israel reported Pfizer cut infection by around 75%, the Mayo clinic had similar. The official U.K. figures are 55-70% after one dose of Pfizer and 70-90% after 2; AZ is 60-70% after one dose and no data yet for two doses.
So those are people who aren’t getting infected, so can’t pass it on. Good start.
Then there’s the question of onward transmission: if you do get it, how likely are you to pass it on?
Studies from March and April put single dose impact on transmission as cutting it by 40-50%, more recent data seems to be nudging it higher 40-60%) and second dose should also have an impact on that.
Obviously Delta isn’t factored into this but we know that two doses still work pretty well against it.
So: if you’re vaccinated, you are much less likely to get infected. And if you’re in the minority who do get infected, you’re much less likely to pass it on - so there’s a cumulative effect.
And of course they are also shit hot at preventing hospitalisation and death which is their primary purpose. And less severe disease = fewer replications = less chance of mutation, so that’s important too.