I thought AZ was poor against Delta.... Or have we been sold a lemon. Again.
As the saying goes (roughly) - torture the numbers and they will say anything.
The same goes with definitions of words. Vaccination, immunization, efficacy..
Vaccine - prior to CV, I (& perhaps most) thought that an 'effective' vaccine would create immunity. So prevent you catching whatever illness/disease/virus that it was designed for. Also that as a consequence - you would not be able to infect others with it after being 'vaccinated'.
None of the various vaccines developed to date for CV, regardless whether old tech (using eggs for example), mixed tech or new tech (mRNA) fit that definition. Someone who is fully vaccinated can still become infected with CV as well as pass it on to others.
Efficacy - again prior to CV, I thought of efficacy as reflecting what proportion of vaccine recipients were made immune to the illness/disease/virus. Whether it is part of the spin-doctoring by the pharma companies or Govts (akin to Microsoft being able to sell faulty software with no liability for problems it causes ie: Windows) the new definition of efficacy has altered.
It has gone from the proportion of people immune and now has around 5 separate meanings depending on the narrative sought for CV. None of those meanings relate to being immune from infection nor immune from onward transmission.
- Efficacy = reducing deaths.
- Efficacy = reducing ICU intervention
- Efficacy = reducing hospitalisations
- Efficacy = reducing onward transmission
- Efficacy = reducing symptomatic infections & making them non-symptomatic instead
Depending on the article or study & the particular 'use' of efficacy then provides different headlines. One of the more reliable versions (from the UK Gov) is that the 1st dose of AZ only has around low 30% (#2 or possibly #3) efficacy against the Delta (or 2nd Indian) variant but I have not re-read the details closely this week. After the 1st dose, AZ has much higher 'efficacy' for the China variant & others bar the South African & 2nd Indian variant.