[csee]

But here you're talking about efficacy against infection and mild disease, which is not so relevant if we're talking about preventing new strains. New strains are thought to evolve in immunocompromised people with high viral loads over long periods of time, which allows both many mutations to occur as well as for those mutations to become dominant. So I believe the question should be to what extent the vaccines help prevent serious disease in people with comorbidities - and the answer is that they help to a great extent (whether 70% or 90%).