Australia could see Covid surge from new variants even after 80% vaccination when border reopens

The Australian International Border should be reopened if highly transmissible Covid-19 variants circulate overseas or locally. Large and disruptive outbreaks may still be possible even after 80% of 16-year-olds have been fully vaccinated according to modelling published in Medical Journal of Australia.
After Dominic Perrottet (New South Wales premier) announced Friday that returning Australians and tourists will be able travel to Sydney from November 1st without the need to go through quarantine at hotels. Later, Scott Morrison, the prime minister, stated that the international border will only be open to vaccinated Australian citizens, their immediate families, and not tourists. He said we won't rush.

Dr Mark Hanly, from the Centre for Big Data Research in Health, University of NSW, conducted the modelling. He used various assumptions about transmissibility, vaccine rollout speeds, and the scale of border opening to determine the impact on hospitalisations and virus cases.

If the scenario assumed an infection similar to that of the Alpha variant, international borders were opened. However, local restrictions such as mask wearing and social distancing did not prevent local transmission. Hanly and coauthors found that severe Covid-19 hospitalizations were very rare in this scenario.

If the virus were to be allowed to enter Australia with a similar level of infectiousness as the Delta variant and when at least 80% of Australians aged 16 or older were fully vaccinated (64%), then the opening of the international border would have a dramatic effect on both hospitalizations and infections. This was true regardless of whether there were 2,500 or 13,000 international visitors per day. The modelling revealed that these surges would require public safety measures other than mask wearing and social distancing in order to not overwhelm the health system.

According to modelling, international travelers could be exposed to new strains of SARS-CoV-2 and chains of infection if Australia's borders are reopened to them.

Politicians and health system officials should not be focusing on setting vaccination thresholds that could be lifted. They should recognize that mass vaccination will not provide complete protection against Covid-19.

Professor Catherine Bennett, chair of epidemiology at Melbourne's Deakin University, stated that it was important to remember that the modeling assumed no virus in Australia as a baseline for variants entering from overseas.

Bennett stated that this is no longer the case. There are already restrictions in place that we will be able to lift, but not completely.

Model also believed that additional public health measures, beyond social distancing and mask wearing, would be introduced only once the number of new cases exceeds 10,000 per day. Bennett stated that it was possible that additional restrictions will be put in place much sooner than what the model predicted.

Bennett stated that it was likely that measures would be taken to prevent us from reaching 10,000 cases. This modeling demonstrates that prevention should be the main focus, not waiting for the virus to get away to implement safety and health measures. The good news is that I believe the proposed international reopening fits within these prevention settings.

Prof Mary-Louise McLaws from UNSW, an expert in infection control and member of the World Health Organisations Covid advisory board, expressed concern about Perrottet's announcement that the NSW international border would be reopened.

McLaws stated that while she is comfortable with the elimination of hotel quarantine, it was important to test all returning Australians for the virus on the day they boarded their plane. Only those who were positive should be sent home. She suggested that those who have tested negative for the virus should be given a rapid antigen test five days a week, and then again five days later.

She said that you have a very low risk of spreading the virus to immunocompromised and unvaccinated people. Even fully vaccinated people are susceptible to the virus.