And if you read the interview you would see it discusses this. First, among vaccinated Delta is getting a root in the nose and throat but your body knows it and is attacking it and destroying it faster than with someone who isn't vaccinated. This means you're contagious for a shorter period of time. There are also those who had a very strong immune reaction to the vaccine that Delta can't even get a foothold on. So there is likely a reduction of the spread.
But the vaccines could be completely ineffective at stopping the spread and they would still be advisable. If they did nothing else than drastically reduce the odds of severe illness then they'd still be insanely beneficial.
As for the decreasing efficacy, it's appearing that what drops is the efficacy against infection while efficacy against severe disease is remaining strong. How much of this decline is due to time and how much is due to Delta being better at causing a mild infection in vaccinated people isn't clear. In any event, the efficacy against severe infections seems to be holding up.
Natural immunity most likely offers stronger immunity than the vaccine alone. However, if the vaccine doesn't prevent you from getting infected with Covid but prevents severe illness then wouldn't it make sense to get vaccinated, guard against sever illness, but still reap the benefits of a natural infection?
