Sure it can. Vaccines are only one part of the puzzle. With 50% population immunity you need far (far) less natural immunity to reach an R number less than one, at which point outbreaks don't grow anymore.

Obviously these magical mRNA vaccines with their 95% numbers are going to be more effective. But that's just a (very) happy scientific accident that they worked out. Historically vaccines haven't been anywhere near that effective and have still controlled disease. Hell, the flu shots we get are like 30% effective and they still save lives every year.