Experts reject Scott Morrison’s Covid-19 transmission claim

Health experts have questioned Scott Morrison’s assertion that there is little evidence to indicate transmission of COVID-19 is preventable.

Medical staff prepare vaccines in the pharmacy area of the NSW Vaccination Centre in Homebush, Sydney. Picture: James Gourley

Health experts have questioned Scott Morrison’s assertion that there is little evidence to indicate transmission of COVID-19 is preventable, saying plummeting daily cases in countries where vaccines have been widely administered indicated that vaccination was halting the spread of infection.

The Prime Minister said at the weekend there was not enough evidence on how vaccines reduced transmission to wind back Australia’s quarantine requirements. “We don’t as yet have considerable clinical evidence that tells us transmission is preventable … and so we have just got to wait for the numbers to come in on that,” he said.

However, a study published in the past week by scientists from the UK executive agency Public Health England, based on 550,000 individuals, found the chances that a positive case would transmit COVID-19 to a household contact was reduced by more than 50 per cent in people who had received at least one vaccine dose.

The study adds to preliminary evidence that has emerged from Scotland, where a study of NHS healthcare workers found that positive COVID-19 cases were at least 30 per cent less likely to transmit the disease if they had received one vaccine dose, and 54 per cent less likely to transmit the virus if they had been fully vaccinated with two doses.

An earlier study out of Israel and published in The Lancet found there was a 75 per cent reduction of infections among 7214 hospital workers who had received one dose of the Pfizer vaccine.

On top of this, daily case rates have declined dramatically in the UK, the US and Israel following mass vaccination programs.

Tony Cunningham, an infectious diseases physician and virologist, said strong evidence was emerging of the vaccines’ ability to interrupt the transmission of COVID-19.

“My summation of the evidence is that there’s promising studies,” Professor Cunningham said. “There are studies showing significant reduction in the spread of infection. These studies need to be further verified.”

Epidemiologist Mary-Louise McLaws said the “remarkable” drop in daily cases in the UK since its vaccination program began amounted to strong observational evidence that vaccines were stopping the transmission of COVID-19 to a significant extent. In early January, a month after its jab drive began, the UK’s third wave peaked with a daily case tally of more than 68,000. Daily case rates are now fewer than 2000.

More than 35 million people in the UK have received one vaccine dose, and 17.6 million people are now fully vaccinated.

“Those numbers tell me they are seeing a really great effect from vaccines,” Professor McLaws said. She said it would be surprising to suggest in the face of these figures that vaccines’ ability to stop transmission was under question. “The Prime Minister’s comments were not really accurate,” she added.