It’s hard to predict arrival times on any long road trip, especially when you are not sure of the destination or the conditions along the road ahead. In a pandemic we know that the journey is shaped by a dynamic interplay between the virus, human host and environment, and that generates unpredictability.
Not good news when the coronavirus has already subjected us to two years of uncertainty, but we are making progress towards emerging from the official pandemic period.
A pandemic is declared when a new human pathogen appears, or with an unexpected rise in the spread or severity of an existing disease that crosses international borders. We can no longer say that waves of Sars-CoV-2 infections are unexpected after two years of global transmission and four major waves, but the other important aspect of calling a pandemic is that it signals the need for global cooperation and resource mobilisation.
It is this that keeps us in pandemic mode with some countries still straining to access vaccines, control waves, or manage the burden on health systems or the impacts of strict control measures.
Eradicating a new human pathogen is the holy grail, but that was always a very long shot for a coronavirus – we knew we would be lucky to create a vaccine that could mitigate the impact of the virus. The virus has now also moved into animal reservoirs, taking eradication off the table.
Whilst the virus has evolved, so have we. Vaccine and infection induced immunity, along with our environmental and behavioural changes, have curbed the disease potential of this coronavirus, and higher rates of infection no longer risk overwhelming our health systems in most parts of the world. Our progress down this path has only been possible because of the vaccines, with high uptake in Australia.
This, together with new monoclonal antibody and antiviral treatments, help keep most infections out of hospital and allow us to provide optimal care to those that do end up there.
The risk of ending up in ICU if you have an infection is now substantially lower than it was in any other time in the pandemic, but of course more people have infections now that community transmission is Australia-wide. We have just under half the number of people with Covid infections in ICU now (133) as we did in October last year (300), even though on average we have over 40,000 new cases reported each day, compared with 2,750 new cases a day in 2021. This equates to a 33-fold reduction in the ICU rate among reported infections in just six months.
Rising vaccination rates over this period is the most impactful prevention measure. Another shift is in the dominant variants, with Omicron often described as “milder”.
However, Omicron is as virulent as early variants, with the lower hospitalisation rate among infections down to immunity and treatments preventing disease escalation, and a study in the US released last week found Omicron to be just as virulent as all previous variants when patient characteristics and vaccination status were taken into account. Omicron being “mild” may therefore be less about the virus and more about our success in managing this virus.
With Omicron’s arrival and the easing of restrictions, Australia has amongst the highest “reported infection” rates per capital in the world, sitting just behind New Zealand. However, if you look at hospitalisation rates or deaths per capita, we are well down the list.
Take the UK, for example. They are further through their BA2 wave, reporting a case rate that is 10% of ours, yet twice the hospitalisation rate. This tells us that it is not possible to directly compare infection rates as some wind down their testing programs. We are in fact likely to have half the infection rate of the UK today.
But Australia’s infection rates are still 15 times higher than with Delta, and even with a smaller proportion of infections ending up in hospital from their infection, the sheer number of cases still translates to higher death counts than we have seen previously.
There is an urgent need to understand more about who is becoming severely ill, and whether this may have been avoidable. The booster doses have been critical for rebuilding protection from serious disease with Omicron, and Israeli data show that this protection is sustained beyond six months.
GPs can now prescribe antivirals, making these readily available to those at risk of severe disease early in their infection. But there may be factors contributing to poor health outcomes that we can address, including delays in diagnosis and missing the critical time window when antivirals can be effective.
Infection rates remain high, with a succession of Omicron variants now increasing the risk of reinfection. It is not surprising that subvariants appeared after massive BA.1 and BA.2 waves hit the northern and southern hemispheres simultaneously – every infection increases the chance of seeing a new variant and new infections peaked at over 3.8 million a day globally on 21 January this year where previous waves never reached a million.
We are not out of the woods yet as it can take some weeks for a new variant to spread sufficiently to be detected. On the upside, to be successful new variants must be even more transmissible than Omicron, and this reduces the proportion that will pose a threat.
I believe we will not know that we have left the pandemic period until after the event, when we have entered a period of greater control of the virus and consistency in variants and our public health responses and, with that, certainty.
We are on the way, but in Australia we need to be sure that preventable deaths are addressed before we set expectations for this disease in the transition out of the pandemic period.
We must also remember that everything we each do to avoid getting the virus, or passing it on, helps us make that transition sooner.
Catherine Bennett is chair in epidemiology at Deakin University.
