Finally a little explanation on what the 33% efficacy of first jab in the Israeli study meant.
1. Data only available to 18 days post first dose.
2. Shows no change to day 12 compared to unvaccinated then 33% less cases per capita each day from day 14 - day 18 if vaccinated.
My take:
1. Good news - the vaccine is indeed reducing cases in the real world post first dose.
2. Bad news... these results are, as reported, not as good as those from the trial.
BUT
3. Not comparable to the trial (1): this includes asymptomatic and we don't know at what proportion, whereas trial was symptomatic only.
4. Far too short a time period to draw conclusions.
5. Not comparable to the trial (2): we have no idea to what extent vaccinated people take more risks, so may just reflect that once people are vaccinated they merrily go around licking other people for the sheer joy of it(!)
6. We don't know how serious these cases were, and reducing severity of infection is the main point of vaccination.
Overall: interesting, but not directly relevant either way to the UK one dose strategy, or long term efficacy.
All just my own views, not remotely definitive, treat with due scepticism.