[rhyzomatic]

The commenter you originally replied to was wrong. Pfizer (and other vaccine researchers) never did research on transmission.

But again, can you cite any sources saying that at one point they [Pfizer and other vaccine researchers] did claim that?

The answer of course is that no, you can't, because they didn't. They didn't lie and neither did governments and health organizations. But because we were asked to vaccinate to protect ourselves and others (which worked, and was quickly backed by independent scientific research after vaccines were offered to the public), it sounds like a big gotcha lie if Pfizer says they specifically didn't research that.

Note there are ways you protect others by vaccinating other than reducing transmission. By significantly lowering your chance of hospitalization, you ensure there are more free hospital beds for those that need it (due to COVID or not).