Now we have data from the AstraZeneca [AZ] trials. Be very cautious in comparing their results with the Pfizer and Moderna data. The AZ protocol is entirely different from the other two. They were testing different doses as they went along. Some people got a full dose initial shot followed by another full dose A smaller group got a 1/2 dose followed by a full dose. In this small group they report 90% efficacy.
VERY IMPORTANT Both Pfizer and Moderna defined a Covid illness as the person had SYMPTOMS and a positive Covid test. They were not tested unless they were symptomatic with something more than trivial symptoms. But the AZ protocol required that the volunteers have PCR Covid tests on a regular schedule whether they had symptoms or not. So the AZ failure rate includes asymptomatic and low symptomatic positives. A 70% efficacy of everyone vs a 90% efficacy for sick prevention is a very different criteria and until the breakdown of positives, symptomatic vs not symptomatic, in the AZ study is made available you cannot use efficacy numbers to decide.
In favor of the AZ vaccine are: Only requires refrigeration, no freezing, no super low freezing. Much less expensive to produce, less expensive to ship and store. The technology is old and has a well established safety profile. While I have no concerns about mRNA, it is new and does not have an established long term safety profile.
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