1) Please news companies report the #COVID19 #vaccine data as risk ratios with confidence intervals to give an indication of the uncertainty around those figures.

2) Risk ratio is the risk of getting the disease when vaccinated / the risk when not vaccinated to for the Oxford @AstraZeneca data this is 30/101 = 0.29 so you are less than 1/3 as likely to get disease if vaccinated

3) 95% Confidence intervals give an indication of how confident we are in that value. Obviously with smaller samples there will be more uncertainty so the CIs will be bigger. For the Oxford @AstraZeneca vaccine the CIs are 0.20 - 0.45.

4) The CIs should be the real headline figure. If vaccinated with the @UniofOxford @AstraZeneca vaccine you are somewhere between 1/5 and slightly under 1/2 as likely to contract disease. Probably.

5) For comparison the values for the Pfizer vaccine are a risk ratio of 0.05 and 95% CIs of 0.024 - 0.100. So this vaccine means that you are somewhere between 1/40 and 1/10 as likely to get disease if vaccinated (insert ob comment about cold storage here yadda yadda)

6) Note all values calculated from publically available data and I'm assuming equal sample sizes for control and treatment groups.

7) So it's quite possible that in fact the Oxford vaccine is "80% effective" and the Pfizer one is "90% effective". It's equally plausible that the true figures are "45% effective" and "97.5% effective". That's how uncertain we are at the moment.

8) It's also quite possible that the true figures lie outside those 95% CIs. For more confidence we could calculate 99% CIs which are 0.17 - 0.51 for the Oxford vaccine and 0.019 - 0.13 for the Pfizer one.