I have been having a little Facebook chat with a friend from UC Davis. He is deep into the middle of the covid vaccine development so I have trust in what he has to say. It took a few back and fourths to get to the nut of the issue, but we finally did – and I want to share it.

The answer is that I am correct about what efficacy means (as discussed in the media it means “preventing sickness”, not “preventing transmission”). They are being careful about what they claim, and he agrees that it is being misunderstood by most people that read and hear what they are saying.

He said the problem is that they haven’t had time to do the human tests necessary to make a claim about preventing transmission. However, they have done enough tests to be confident that it will prevent transmission by about 99%. But that is based upon assumptions and some science that point in that direction.

His educated opinion is that it will work, and work at an effectiveness for preventing transmission of about 99% . That is very good news. It means if they can manage to vaccinate about 50% to 60% of the population it will be over with because of the creation of sufficient herd immunity. So maybe there is actually a light at the end of the tunnel.