COVID-19 boosters are ‘definitely worth it', says leading epidemiologist

Australia is set to expand the eligibility criteria for the fourth vaccine or second booster dose.

Australia has expanded the eligibility criteria for the fourth vaccine or second booster dose. Source: Getty Images

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Professor Catherine Bennett, Deakin University chair of epidemiology, says the previous Omicron infection will not prevent people from having a new infection.


Edited excerpts.

Question: Professor Bennett tell us briefly about the current COVID-19 situation in the country.

Answer: We are concerned that new variants are pushing our infections up again. These latest BA.4 and BA.5 Omicron subvariants are similar to earlier ones, but infection rates are rising again. They cause a similar disease to 2020 strains, but thankfully this is less likely to put as many in hospital because of our high levels of immunity in the population.

But the BA.5 might be a bit different. It looks like it's more efficient at binding to proteins in our respiratory linings, can more easily infect our lungs. It means BA.5 may be more likely to cause lower respiratory tract infections in people. Other Omicron variants mainly cause a throat infection, a sore throat, and cold-like symptoms with a fever.

Question: So, what do we know about these new variants? Can they evade immunity from previous infection and current vaccination?

Answer: Both. And that's the frustrating thing. Infections from the Delta variant didn't protect people from infection from Omicron. Interestingly, Omicron doesn't save us from itself.
So, if you had an Omicron infection, it doesn't stop you from having another Omicron infection.
We're in this winter of a succession of variants, each having a little bit more immune escape, and that's the challenge for us.

We have to ensure people have all their recommended boosters because the booster gives you a bit more cross-immunity and protection from Omicron. It reduces the risk of serious illness quite dramatically. The winter booster dose brings down the serious infection risk by another two-thirds in people at the highest risk who might now also have less protection from their first booster.
Professor Catherine Bennett.
Deakin University chair of epidemiology Professor Catherine Bennett. Source: Supplied by Professor Catherine Bennett
Question: How serious could it be for people who catch the virus again?

Answer: Well, it's a good question. The way you develop an infection depends on the infecting dose. If you are exposed to just enough virus to start an infection, you might be able fight to it off quickly and have mild symptoms, or even none at all, because you've got some immunity. This is more likely if you’re young and healthy and have had your first booster.

But we're hearing some people get pretty unwell on their second infection. And it may be just that they got a big infecting dose, or due to a different variant. We are also worried that repeat infections, the fact you might have two or three in quick succession, could increase your risk for long COVID.
Everyone should avoid infections irrespective of age and past experience with infection. Wear masks when you're around other people and try to follow those measures that have worked for you in the past.
Currently, the exposure risk is high because of higher infection rates. For example, it is now much more likely that when you walk into a city shop where 25-30 people are present, one of them will have COVID without even knowing it.

Question: You are suggesting people wear face masks and maintain social distancing. What about the federal and state governments that have been winding restrictions? Should restrictions be reintroduced?

Answer: I think we've been told what to do for the last two years. But in reality, and longer-term, what's going to be sustainable is actually making sure people have the information they need to make those safe choices. Rules are starting to wear very thin, but it’s important people have the information they need to understand and manage their risk.

Question: But do you advocate restrictions be brought back, maybe partially?

Answer: I think we haven't seen any appetite for that from the government now. I think they (the government) have a sense that even if they do, most will not do it. And there's no enforcement. The fewer than 50 per cent of people wearing masks on public transport now, where masks are still mandated, probably would wear them whether there's a rule or not, and those who aren't wearing them now on transport, probably wouldn't if mask rules were widened.

I think it's got to be something else going ahead. We need better information and more active surveillance. So, we know the variants circulating in our communities and the actual risk of catching the virus.
I also think working with community leaders and thinking about protection and prevention. In fact, like with vaccines, the actual investment should be in prevention.
There can be partnerships between communities and public health units. Health Department could try to get the information that makes sense to people or answers the questions that your readers and listeners bring to you.

Question: ATAGI has recommended the fourth dose or a second booster dose for people aged 30 and over. How do you see this development?
 
Answer: For the first two months or so, a second booster reduces infection rates and may help reduce the number of infections or reinfections we have through winter. People in their 30s have some of the highest reported infection rates. Boosters can also help reduce symptoms and the risk of an infection developing into more severe disease as well. That gets more important as you get older, so that is why ATAGI may recommend the fourth dose for anyone 50 and over now. 
Question: There's confusion among people whether they should wait for a new vaccine that targets Omicron or just get their third or fourth booster dose.

Answer: So if people haven't had their third dose yet, absolutely, that's time to do it. If you put it off because you've had infections, you need to know that those infections don't protect you from further infection.

The vaccine will reduce your risk. So, it's definitely worth doing that. Data reported from Victoria last week showed that 72 per cent of people who died from COVID-19 had not yet received their three doses.

A lot of them only had one or none. Some of them might be too unwell to have a vaccine, but if it includes people who, by choice, didn't have a vaccine, or their family thought it wasn't good for them to have a vaccine, and that's very sad if it might have been the difference between surviving the infection, and not.

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