Sweden and Denmark both stopped Moderna jabs for younger people due to heart side effects. History may show that the jabs injured more young people than they helped. Though jabbing children is likely beneficial to the elderly as it may reduce transmission to them.
With all due respect, there are zero studies or evidence showing the vaccine slows transmission in any way shape or form. They only use the percentage of positive test results which are biased towards unvaxxed. The problem with that data is we test unvaxxed at a rate of three to one or higher. Vaxxed people are not tested unless very symptomatic.
My spouse is a primary care Dr and sees over 400 patients a month. She has treated in the thousands of Covid cases since the beginning.
Her hypothesis-and one shared by numerous other local physicians-is the vax has propagated the delta surge.
Vaxxed people are more likely to be infected and be asymptomatic. They do not get tested and go about their lives infecting many they come in contact with. Unvaxxed can do the same, but if we believe what the CDC says then the vaxxed are even more likely to be silent spreaders.
In order to show the vax reduces your risk of infecting someone else, they would need to take a sizable cohort of vaxxed people with a similar cohort of unvaxxed and test them several times a week to see if the vax actually prevents infection. This test/study has not been done yet and there is not a single one planned that we can find.