Researchers say implications for transmission remain unclear but reaching herd immunity even more challenging
Fully vaccinated adults can harbour virus levels as high as unvaccinated people if infected with the Delta variant, according to a sweeping analysis of UK data, which supports the idea that hitting the threshold for herd immunity is unlikely.
There is abundant evidence that Covid vaccines in the UK continue to offer significant protection against hospitalisations and death. But this new analysis shows that although being fully vaccinated means the risk of getting infected is lower, once infected by Delta a person can carry similar virus levels as unvaccinated people.
