Vaccine efficacy is against severe COVID illness, not against transmission. The vaccine is still effective, although recent studies indicate that after 6 months it may only be 50% effective against severe illness (this will vary tremendously for each individual).
This is a non-sterilizing vaccine. It was never designed to stop transmission. It did surprisingly block transmission pretty well before the Delta variant. The theory presented here is that the vaccine effect takes time and kicks in on around day 5. With Delta the virus has already become highly transmissive by then. Pre-delta that probably was not the case.
This is a non-sterilizing vaccine. It was never designed to stop transmission. It did surprisingly block transmission pretty well before the Delta variant. The theory presented here is that the vaccine effect takes time and kicks in on around day 5. With Delta the virus has already become highly transmissive by then. Pre-delta that probably was not the case.