Even if effectiveness wanes, vaccines are still our best defense against new COVID strains

New COVID-19 variants are circulating in Australia, but vaccines still provide a vital line of defence against both infection and reinfection with the disease.

First detected in Melbourne wastewater in April, the COVID-19 subvariants known as BA.4 and BA.5 are set to drive Australia’s newest wave of infections this winter. These strains appear more transmissible than the preceding BA.1 and 2 that prevailed at the beginning of the year, but while they may not lead to a dramatic spike in case numbers, they could present new symptoms.

“BA.5 could be potentially better able to cause worrying symptoms,” explains Deakin University chair in epidemiology Professor Catherine Bennett. “Instead of an upper respiratory cold where you get a sore throat and you’re blocked up, you might get something that is more likely to potentially lead to a lower respiratory tract infection, particularly in more vulnerable people.

“And we don’t want to see that in large numbers. That is what could overwhelm our hospitals if that proves to be true. It’s really important that we do try and keep a cap on infection. But that’s really hard to do in the middle of winter.”

Unsurprisingly, prevention is better than cure when it comes to COVID-19 and the established hygiene practices that have been a staple of the pandemic’s management are still recommended.

As recently as Tuesday, New South Wales chief health officer Kerry Chant emphasised the use of face masks, hand hygiene, testing for symptoms and physical distancing to prevent transmission of the disease.

But without the same level of case reporting that many were accustomed to amid the first two years of COVID-19, it may seem unclear how Australia is faring compared to the rest of the world.

So, what’s the state of play for COVID-19 in Australia as BA.4 and BA.5 come to the fore?

Big jump in case numbers – and deaths – since start of the year

While remaining low-level restrictions continue to ease across the country, and total deaths from COVID cleared the 10,000 mark this week, Australia’s small case-fatality rate is something to celebrate.

“It’s 0.2%,” says Professor Adrian Esterman, Professor of Biostatistics and Epidemiology at the University of South Australia. “That means 0.2% of all cases end up dying. By international standards that’s low.”

But that, Esterman points out, doesn’t tell the whole story of how Australia is coping with the pandemic.

Right now, Australia’s average weekly fatalities from the disease are comparable to nations like France and Spain – and much higher than other high-income nations like Japan, Canada and New Zealand.

In fact, since the start of the year, the number of COVID-19 deaths in Australia has increased by around 400%.

“In terms of actual numbers, we have very, very high numbers of deaths compared to other countries, and that’s because we have so many cases,” says Esterman.

For context, Australia has reported roughly the same number of cases in 2022 as Taiwan – a country that crams roughly the same number of people into a landmass over 215 times smaller. Only France, the US, Germany, Italy and Brazil have reported higher case numbers in the first six months of this year.

The challenge for Australia now is how it will navigate the rest of winter with more transmissible strains circulating, the return of seasonal flu, and currently available vaccines that become less potent with each new mutation of the virus.

Three jabs are better than two, even against BA.4 and BA.5

We’ve all heard the same thing: once you’ve recovered from COVID-19, you have three months of immunity before you’d be a chance to get it again. But how does that stack up in reality?

New Zealand’s health department now says it’s possible that COVID-like symptoms experienced a month after recovery could indicate reinfection with the disease.

The Kiwis’ advice update, says Bennett, is consistent with the rise of new subvariants: a person recovered from BA.1 in March is unlikely to have the same level of resistance to BA.4 or BA.5.

“In reality… we’ve now got a new variant that’s reduced your protection if you’re someone who’s had an infection in the last month,” she says. “That’s the sort of information that people go, ‘Oh, okay, I can’t be complacent anymore, that variant has taken away my protection’.”

Even if new variants reduce the effectiveness of your hard-earned immunity, vaccination still provides an important barrier to infection.

While more than 95% of Australians over 16 have had two doses of the vaccine, around six million people are yet to receive the booster. That third shot has been found to give a barrier to infection for a few months, even as new variants emerge.

“Because the [first] vaccines were developed on the first variants in 2020, they have had waning immunity against all subsequent variants,” says Bennett. “But the good thing was those first two doses did protect from serious illness even with Omicron, and when you have the booster it bumps it back up to a good level of protection, around 80% or 90%.

“With the booster, though, we discovered it does reinstate some protection from having any infection… up to about two months you get a reduced infection risk by about half. Having that protection can reduce your chance of having multiple infections.”

People over 65 are eligible for a fourth jab – the ‘winter booster’ – in line with current advice from the Australian Technical Advisory Group on Immunisation (ATAGI), but this recommendation is yet to extend to those aged 16–64.

Next generation vaccines targeting Omicron variants are expected to be in production by the end of the year.