Fully vaccinated people can pass on the Delta variant at home, including to other vaccinated people

Fully vaccinated people can catch and pass on the highly infectious Delta variant at home, including to other vaccinated people - real-world data shows.

A study, led by Imperial College London and published in Lancet Infectious Diseases, identified 71 people who had caught COVID-19 caused by the Delta variant.

Out of these people's fully vaccinated household contacts, 25% caught COVID-19, compared to 38% of their unvaccinated household contacts, the study found.

Ajit Lalvani, chair in infectious diseases at Imperial College London, who co-led the study, said in a statement that vaccines were "not enough" to stop people getting infected with the Delta variant and spreading it at home. "This is likely to be the case for other indoor settings where people spend extended periods of time in close proximity," he said. Fully vaccinated people become more susceptible to COVID-19 within a few months after the second vaccine dose. The study provided important insights into why the Delta variant was causing high COVID-19 case numbers around the world, even in countries with high vaccination rates. Continued public health and social measures to curb transmission thus remain important, even in vaccinated individuals.

If you want to avoid being infected you still need to do everything you can to avoid close contact, wear a mask and wash your hands even if you have been vaccinated.

Dr. Simon Clarke, associate professor of cellular microbiology at University of Reading, said in a statement that vaccines "drive down" COVID-19 infections, but were "not a silver bullet." "Infection in the wider community can still be amplified by transmission at home," he said. Clarke cautioned that it would be a "grave mistake" to assume that households were the only place where transmission occurs.

The researchers from Imperial College London, Manchester NHS Foundation Trust, and the UK Health Security Agency used the UK's central contact tracing system to identify 621 participants and tested them for COVID-19 regardless of symptoms with a lab test. Of the 621 participants, 163 had COVID-19, and 71 of these were caused by the Delta variant. Of those infected with Delta, 54% were fully vaccinated, 32% were unvaccinated and 14% had received one vaccine dose, the study authors said.

Original paper