Originally Posted by
Lead Balloon
Mick: On your definition of "efficacy", is the efficacy against Delta in Israel 42% for those double vaccinated against Covid 19?
It's not
my definition. Per the diagram below there are a variety of endpoints for measuring efficacy. The Israeli number is for infection, likely symptomatic infection. From a public health perspective the most important efficacy endpoint is protection against severe disease and death.
Protection against severe disease is typically measured by hospitalisation rates and ICU admission rates. On those efficacy endpoints both Pfizer and AstraZeneca are proving to be around 90 percent effective. I haven't refreshed the numbers recently but last week, Israel had 11,200 active cases but only 101 hospitalisations and 24 ICU admissions. Out of that case load they were only seeing one or two deaths a day.
That is an extraordinary improvement over their pre-vaccine experience. The pre-vaccination hospitalisation rate in Israel ran at about 15 percent; a week ago is it was less than one tenth of that (that is, one order of magnitude better) at around 1 percent.
While not perfect, the seat-belt analogy might be appropriate - compared to not wearing one, your risk of serious injury or death is markedly lower. I don't know how many people who walk away from what would otherwise be a fatal prang and complain about the sore shoulder and the bruising across their midriff as an indicator of poor efficacy.