The effectiveness against Delta is still not clear.
The problem is that, to measure effectiveness, you need to see the spread in a mostly unvaccinated population. The population which was exposed in Israel was > 80% vaccinated.
The reason is that having 80% vaccinated provides extra protection to the unvaccinated, that they do not have in, say, Louisiana, and that they did not have in the populations in the UK that was being infected.
So, in an unvaccinated population, a vaccinated person will have less than 10% the chance of an vaccinated person at being infected.
What can be calculated a lot more accurately, no matter how many people are vaccinated, is the percent of people who tested positive who were hospitalized, and the percent of the hospitalized who died.
That is why they are able to say how much it protects against hospitalization and death.
A second issue is that almost all the elderly people in Israel who were infected were vaccinated back in Dec-Jan, so they have > 6 months since the second vaccination.
Bottom line, it is very difficult to estimate the effectiveness of a vaccine, when the great majority of the population is vaccinated.
Regarding scientists and messages, there is a huge problem in the USA, that a huge segment of the media and politicians who have been doing their best to push the idea that Everything Is Opinion. This has come from across the political spectrum, mind you.
That means, that, when scientists revise what they think is happening, people then criticize them for “flip-flopping”. And when Fauci changes his message, based on changing information, people are criticizing him for “flip-flopping”. When COVID deniers, keep on repeating the same fake stories that have been debunked a dozen times, they are respected for keeping the same message.
I mean, scientists used to think that electrons, protons, and neutrons were the fundamental particles of the universe. Now they know that they are not - is that “flip-flopping”?
At the same time, people who reject science, whether it’s regarding COVID, “alternative healing”, young universe, etc, follow people who are repeatedly proven wrong, because these people do not change their message.
Basically, large number of people in the USA, would rather follow a person who denies the facts that contradict their claims, than follow a person who revises their claims in the face of facts.
Why? Because the second person is “flip-flopping”. Because a person who makes up “facts” match their claims is “resolute” and “strong”.
Bottom line (for this part of the discussion), changing the message to fit the facts is NOT “flip flopping”. It is, in fact, a little thing called “intellectual honesty”, something which too many people in this country do not respect at all.