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Restricted group | Started - August 2018 | Last activity - This week

Effectiveness of COVID-19 vaccines against hospital admission with the Delta (B.1.617.2) variant

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I see that the HR estimates were calculated using adjustment for various factors, such as the age. Has there been any considerable variation of HR values across various ages? 

Why is there no data comparing to unvaccinated and previously infected without vaccination?  This report only shows results for those that have received vaccines.  This report would be more well rounded with additional data showing these 2 new variables with corresponding odds ratios.

Is the 2 dose AZ vaccine interval 12 weeks?

The sample size in this study is to small and in fact this is a poor study that does not prove what it says it does. I expect better from the government.

I absolutely agree with Mark Zlochin. It would be very interesting to compare the vaccine effectiveness in various age groups.

Where are the comparisons to the unvaccinated? Why was this group not included?

I believe the Hazard Ratio (HR) and Odds Ratio (OR) and therefore Vaccine Effectiveness (VE) are defined with respect to unvaccinated people - so this group is included by definition. They explicitly state this for the HR in the last sentence of page 1.


When they claim a vaccine effectiveness of e.g. 96% for 2 doses of Pfiser this means that if you catch the virus, you are 96% less likely (i.e. ~20 times less like) to be hospitalised if you take the vaccine compared to if you don't. Someone correct me if I'm wrong- I had to google HR and OR! On the other hand there seems to be enormous variability in the data e.g. HR=0.34 (0.10-1.18). Does anyone know if the number in brackets represent the variation with age group?