In the same way that seatbelts don't stop deaths from motor vehicle accidents but do significantly reduce them, vaccines don't stop transmission but they do significantly reduce the transmission rates.
Similar statistical model as control rods in a nuclear reactor - they don't stop neutrons, they significantly reduce the numbe of free neutrons flying about and avoid an exponential increase and runaway chain reaction.
Similar statistical model as control rods in a nuclear reactor - they don't stop neutrons, they significantly reduce the numbe of free neutrons flying about and avoid an exponential increase and runaway chain reaction.