The realistic goal is also not to prevent transmission but to prevent severe disease and death, and a 4th shot won't help much with that at all.
Once everyone has T-cells the pandemic phase is over and it really does just become a cold or the flu and we're getting close. Estimates are that around >90% of the population is exposed or vaccinated. Once we get there then the reaction to the virus should look more like a cold or flu virus. We don't recommend anything for colds. For the flu we mandate it for health care workers and highly recommend it for vulnerable people and offer it to everyone. We're going to wind up there soon.
There's also going to be a narrower number of people who have been vaccinated and never caught the virus who think that the goal is zero covid, sooner or later nearly everyone catches it. Once they've been vaccinated and caught mild disease they're going to stop treating it as an existential threat. Once that happens their appetite for supporting mandates will disappear.
My guess is that Omicron is the last gasp of the pandemic phase of the virus. And I can't see mandates for 4+ shots being anything other than political suicide in the US outside of health care.
Right, see, the issue is that these people who want Zero COVID but are just slightly bothered by that never having been the stated goal are planning to go down fighting.
Why would any other country stop with 1 booster? I think rather that they are just slow rolling their mandates. The data suggests that the immune boost is temporary so I don't see how the situation will be any different for shot 4.
Perhaps the only difference will be increasing fatigue with compliance.