Covid-19: Fully vaccinated people can carry as much delta virus as unvaccinated people, data show

BMJ 2021 ; 374 doi: https : //doi.org/10.1136/bmj.n2074 (published August 19, 2021)

Commentary

Adults vaccinated against SARS-CoV-2 may carry the same amount of the delta variant of the virus as unvaccinated adults, according to a study, a preliminary analysis of UK data suggests.

This is the latest result of the UK covid-19 infection study, which shows that two doses of vaccine are also an effective way to protect against delta, but those infected with the delta variant may carry similar virus levels as unvaccinated people, the data showed.

The study authors said the impact on transmission was unknown, but said fully vaccinated individuals could transmit the virus to others, making herd immunity more difficult to achieve.

The analysis, published as a preprint and not yet peer-reviewed, confirmed that both the Oxford-AstraZeneca and Pfizer-BioNTech vaccines provided superior protection against new infections, but performed worse against delta than alpha, which was dominant.