British Study Finds Delta Variant Can Be Easily Transmitted By Vaccinated People In Households: Report

"Immunity wanes over time, it is imperfect, so you still get transmission happening, and that is why the booster programme is so important", Epidemiologist Neil Ferguson said.

New Delhi:  A new study by the Imperial College London on Thursday has found that the Delta coronavirus variant can transmit easily from vaccinated people to their household contacts although contacts were less likely to get infected if they were vaccinated, Reuters reported. 

The British study illustrates how the highly transmissible Delta variant can spread even in a vaccinated population but stated that the vaccination is best for reducing serious illness from Covid-19 and said booster shots were required.

"By carrying out repeated and frequent sampling from contacts of Covid-19 cases, we found that vaccinated people can contract and pass on an infection within households, including to vaccinated household members," Dr Anika Singanayagam, co-lead author of the study, told Reuters.

They found infections in the vaccinated cleared more quickly, but the peak viral load remained similar to the unvaccinated.

"Our findings provide important insights into... why the Delta variant is continuing to cause high Covid-19 case numbers around the world, even in countries with high vaccination rates", Reuters said. 

For the study, about 621 participants were enrolled and found that of 205 household contacts of people with Delta Covid-19 infection, 38 per cent of household contacts who were unvaccinated went on to test positive, compared to 25 per cent of vaccinated contacts.

Vaccinated contacts who tested positive for Covid-19 on average, had received their shots longer ago than those who tested negative, which the authors said was evidence of waning immunity and supported the need for booster shots.

Epidemiologist Neil Ferguson said that the transmissibility of Delta meant that it was unlikely Britain would reach "herd immunity" for long.

"That may happen in the next few weeks: if the epidemic's current transmission peaks and then starts declining, we have by definition in some sense reached herd immunity, but it is not going to be a permanent thing," he told reporters.

"Immunity wanes over time, it is imperfect, so you still get transmission happening, and that is why the booster programme is so important", he added.