Delta dawn: Australia’s new reality living with Covid-19

Picture: NCA NewsWire/Bianca De Marchi

The deteriorating situation in NSW means the prognosis for the rest of the country is now guarded. Even with mass vaccination, a return to Covid zero is unlikely.

From the outset, NSW spurned elimination, choosing a lockdown-lite model, characterised by a gradual escalation of targeted restrictions rather than a bundled, broadbased approach delivered at speed. The rest of the country cycles through short, sharp lockdowns, while the people of NSW face protracted uncertainty along with suffering and death.

The real issue, however, is that the implicit and now explicit abandonment of Covid zero risks the contagion in NSW spreading to the rest of the country. Australians may be living with Covid sooner than we think.

So, what can we do? Getting vaccinated is the priority. Public Health England reported on June 14 that two shots of AZ or Pfizer were highly effective at preventing the most important outcome, hospitalisation, at 92 per cent for AZ and 96 per cent for Pfizer in 14,019 people infected with Delta.

This is important because the Delta variant may be more virulent than its predecessor, Alpha, associated with nearly double the risk of hospitalisation in unvaccinated people based on data from Scotland, Canada and Singapore. Lab experiments show that Delta enters human cells much faster (it is more “fusogenic”), allowing the virus to evade neutralising antibodies, and causes more damage (it is more “pathogenic”), making cells coalesce into large sheets called syncytia. Infected hamsters became sicker, losing more weight and developing more lung damage compared with the parental virus.

Both vaccines are effective at preventing the flu-like illness characterised by fever, runny nose, headache, sore throat or cough, with Pfizer slightly better – at 79 to 88 per cent compared with 60 to 67 per cent for AZ – against Delta based on Scottish and UK data.

As for preventing death, the results are outstanding at 95-99 per cent for Pfizer and 75-99 per cent for AZ based on a report from Public Health England on July 29, when Alpha was dominant. The triumph of vaccination has seen an estimated 60,000 deaths and 62,000 hospitalisations averted in the UK using 57 per cent AZ (48 million doses), 41 per cent Pfizer (34 million) and 2 per cent Moderna (1.7 million) in their campaign.

Whether this first generation of vaccines reduces transmission is now uncertain, making herd immunity a fading hope. Public Health England and the US Centres for Disease Control and Prevention report that viral loads in vaccinated and unvaccinated people infected with Delta are similar but clear faster after 6-7 days in vaccinated people. This prompted a U-turn on July 27 by the CDC, which reinstated its guideline on masks indoors even among vaccinated people.

It is not surprising given that Delta generates extremely high viral loads – 1000 times higher and detectable two days earlier compared with the original strain – and sheds for longer (18 days versus 13 days), indicating that people are highly infectious sooner and for longer.

Encouragingly, the UK REACT-1 study showed that vaccination (specific type not given) reduced the risk of Delta infection by 50-60 per cent compared with unvaccinated people. Pulling the threads together, this generation of vaccines will reduce your chance of getting infected, but once infected with Delta you may still transmit the infection to others but, above all else, your risk of hospitalisation and death plummets.

While the focus now is on preventing the loss of life, interest is turning to breakthrough infections because they provide a glimpse into what living with Covid may look like. Defined as occurring at least two weeks after the second shot, breakthrough infections were reported in 12.5 per cent of fully vaccinated persons by Public Health England on July 23. As expected, they have tended to be mild or without symptoms.

It was hoped that vaccination would wave long Covid goodbye but emerging, albeit very limited, evidence suggests otherwise. In a small study of 39 fully vaccinated young (average age 42 years) healthcare workers from Israel with breakthrough infections caused mostly by Alpha, a handful (19 per cent) developed persistent symptoms (loss of smell, fatigue, breathlessness, muscle pains) requiring two to six weeks off work. This is a space to watch as it will have implications on our economic recovery. Retention of masking indoors will further reduce transmission so should be continued until that Delta wall of immunity is a mile high and a mile wide, hopefully with boosters, vaccinating children and other mitigations like improved ventilation.

We had envisaged transitioning to living with Covid on our terms but the evolving crisis in NSW may well force our hand. The government’s failures in vaccine procurement mean we are now cornered and, unlike our peer the UK, faced with limited vaccine options. With vaccine scarcity the greatest barrier, the government petitioning other countries including the Biden administration – after I raised it in this masthead on May 3 and following calls by Labor – is a welcome development. Until then taking whatever vaccine is available in consultation with your doctor is advisable as Delta is not the Covid of 2020.

Dr Michelle Ananda-Rajah is a general medicine and infectious diseases specialist in Melbourne and is the Labor candidate for Higgins.