In addition to the northern beaches cluster, an airport shuttle driver became infected this week. We have seen numerous staff working in hotel quarantine become infected. Yet the ongoing denial of airborne transmission has hampered our efforts to mitigate risk. In South Australia, the chief health officer acknowledged the role of ventilation in a hotel quarantine outbreak.


Until we address airborne transmission, we fail to address masks and ventilation and keep peddling the myth that washing hands and wiping surfaces is enough. We need universal masking in closed public spaces, a position the US Centres for Disease Control and Prevention has belatedly adopted in the face of catastrophe and mass death. Universal masking reduces the risk of transmission from someone who is infected and also protects well people. It is a low-cost, low-risk intervention.

Clearly, hotel quarantine, like aged care and health care, is a high-risk occupational hazard, and yet we see victim-blaming of hotel staff who get infected. We need to address occupational safety of our health workers, aged care workers or hotel quarantine workers.

The cleaner who became infected working in hotel quarantine in Darling Harbour wore a mask on her long commute to and from Minto. In doing so, she probably saved others from getting infected. Yet today very few people in Sydney wear masks. During the Victorian second wave, about 40 per cent of people in Sydney wore masks, but this has dropped to very low levels just as we head into the holiday season.

The two interventions that reduce the risk of airborne spread are respiratory protection and ventilation. The shuttle driver was reportedly wearing a mask, and still got infected, highlighting that in a small, closed, indoor space, the risk of airborne transmission is high. Good ventilation and a respirator are needed for people at high occupational risk.


If we accept airborne spread, we should be selecting quarantine hotels based on ventilation – buildings built in the past five years will be compliant with current ventilation standards, and older buildings with windows that can be opened may also be suitable. In between, most buildings are not fit for purpose. They allow respiratory aerosols to accumulate indoors, especially in corridors and elevators. Even new buildings will likely have their ventilation set to mostly recirculate air, because drawing in fresh air and maintaining climate control is expensive.

The only exit strategy is a vaccine with high enough efficacy to achieve herd immunity, with most of the population vaccinated. Herd immunity cannot be achieved through natural infection – that is a myth propagated by misinformed people. It is a concept that arose from vaccination. In the pre-vaccine era, no infection controlled itself through herd immunity. Not smallpox. Not measles. Not any epidemic infection. They caused ongoing, massive epidemics, over and over, until vaccines were used.

Vaccines generate more robust immunity than natural infection with SARS-COV-2, and we have promising results from several vaccines. With more than 48 in development globally, they will vary in efficacy and safety, so we should diversify our portfolio.

A vaccine with 90 per cent efficacy in preventing all infection can achieve herd immunity if 66 per cent of the population is vaccinated.

A vaccine of 60 per cent efficacy against all infection will need 100 per cent of the population vaccinated, which is not achievable. If it is less than 60 per cent, herd immunity cannot be achieved, so we need to be strategic in selecting high efficacy vaccines.

Getting 66 per cent of Australians vaccinated is a feasible goal. We should settle for nothing less. If we do, we will be living with COVID-19 – and all the restrictions and costs that come with it – for a long time yet.

Professor Raina MacIntyre is the head of the Biosecurity Research Program at the Kirby Institute, UNSW Medicine.

Professor Raina MacIntyre is the head of the Biosecurity Research Program at the Kirby Institute, UNSW Medicine.

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