https://www.cnn.com/2021/09/17/healt...ing/index.html

Pfizer/BioNTech, which is arguing that there's enough evidence of waning immunity to justify giving booster doses to people
Just some food for thought. If someone's thinking about taking that first dose to keep their job or whatever, they seriously need to ask themselves if they're committed to taking a potentially endless series of boosters multiple times a year.

The Israelis dutifully took the first two with the assurance that it would provide long lasting immunity. Before they knew it, they were back to being second class citizens if they refused to take a third. Now they're about to be ordered to take a fourth:

https://www.axios.com/israel-potenti...367459539.html
https://www.independent.co.uk/news/w...-b1915076.html

But even that seemingly won't be the end of it. The vaccine manufacturers are already developing a Delta specific booster: https://investors.biontech.de/news-r...am-light-delta

While Pfizer and BioNTech believe a third dose of BNT162b2 has the potential to preserve the highest levels of protective efficacy against all currently tested variants including Delta, the companies are remaining vigilant and are developing an updated version of the Pfizer-BioNTech COVID-19 vaccine that targets the full spike protein of the Delta variant.
Just to put that into context, the very same people who are right now lobbying the FDA to force Americans to take a third shot are spending hundreds of millions of dollars developing an entirely new vaccine, that's going to come with entirely new unknown risks. And I would venture to say it's only logical that they're not making this investment without a very high degree of certainty that the product is going to be used. That is, they're not developing it "just in case" as the press release would have us believe. For-profit companies DO NOT develop products "just in case" they might be needed. They only develop new products when the need is crystal clear, and they're near 100% certain the demand will be there if they can successfully bring it to market.

So it looks like best case scenario right now, the mandates will include a third shot, possibly followed by a fourth, which Americans might be spared from if the Delta specific vaccine is available before the fourth shot mandate gets handed down. And it seems only logical to assume there will be boosters of that, as well, followed by future variant specific vaccines.