Why we still need to be COVID cautious

By Professor Stuart Berzins

UPDATED

We are now starting to see some light at the end of the COVID tunnel and, with very low rates of the virus, Australians are now allowed to visit pubs and supermarkets without masks.

Best of all, we are all soon to receive a highly effective vaccine that promises to protect us from serious symptoms. So, can we let down our guard and simply forget that 2020 ever happened? Can we just return to the way we used to live our lives without the worry of social distancing and the like? Unfortunately, not just yet. Here’s why.

1. Not enough people will be vaccinated to achieve herd immunity anytime soon

   It will take time to vaccinate millions of people. The government now estimates most eligible people will have the opportunity to be vaccinated with at least one dose by the end of 2021. Remember though that the vaccines require two doses to be fully effective. That means early in 2022 is our best-case scenario for getting people fully vaccinated on schedule. This is pretty good news but we are not planning to vaccinate anyone under 18. This may change as more trials are conducted, but in the meantime, 25 per cent of our population will not be vaccinated, even if everyone who is eligible gets their shot.

   Of course, the numbers are actually likely to be lower than that. For different reasons, not everyone will choose to be vaccinated. In February 2021, 20 per cent of Australians said they didn’t want to be vaccinated at all. The reasons range from anti-vaccination conspiracy theories to complacency, but regardless of motivation, our best-case scenario might be only about 60 per cent of the population vaccinated. This seems good, but a pandemic where 40 per cent of the population is vulnerable to infection would still be very serious.

   There has also been concern that the AstraZeneca vaccine is associated with a very rare clotting side effect. The Australian government now recommends that people aged under 50 receive a different vaccine but securing alternative vaccines will cause further delays and public confidence could easily be dented. It will be important for the government to keep the public fully informed so that everyone remains confident in the vaccination program and doesn’t lose sight of the fact that the risk of serious side effects remains far lower than the risk of not being vaccinated during a COVID-19 pandemic.

   Of course, not all of the people who are vaccinated will be fully protected, so we still need to be careful after being vaccinated. Most people aged over 50 will receive the AstraZeneca vaccine, which is highly effective at preventing serious disease from COVID-19 infection. Despite concern about rare side effects, it’s a vaccine with an impressive safety profile and is probably about 75 per cent effective. This means that a proportion of individuals who receive the AstraZeneca vaccine could still become infected (and possibly be infectious), although most will be protected from developing serious disease themselves. The effectiveness varies for other vaccines, but some recipients will always remain at risk of infection.

   Taking all that into account, if all goes to plan, we can hope for about half of our population to be vaccinated by early next year, which leaves plenty of people who are not fully protected. That is far better than having no protection and the most vulnerable individuals are prioritised for vaccination, but herd immunity requires at least 80 per cent of the population to be vaccinated, so our community will still be vulnerable to this pandemic.

2. We don’t know how long the vaccine will provide effective protection

   The vaccines approved for protection against COVID-19 are safe and effective, but an unavoidable compromise in developing vaccines quickly is that we don’t yet know how long the protection lasts. Some vaccines, like polio, last a lifetime, but others like the flu need annual boosters. We know the COVID-19 vaccines are effective for at least a few months after vaccination, but it is likely that protection will reduce as time goes on. Vaccine manufacturers have anticipated this and are developing improved versions of their vaccines and evaluating the need for booster shots. It is undeniably great news that the vaccines we have are effective, but we can’t assume they will stay as effective as time goes on.

3. We are likely to see more outbreaks

   Australia is one of very few countries where COVID infections are low. In the US, almost 25 per cent of people have received at least one vaccination, yet the infection rate is still more than 50,000 per day and has recently started to rise. Many other countries have barely started vaccinating their citizens and so there are many, many reservoirs of the virus throughout the world and many scientists now believe it is impossible to eliminate it. We have a great advantage of having very few infections and as an island we can control our borders better than most countries, but with the virus everywhere in the world, new infections in Australia are probably unavoidable. The likelihood of new outbreaks will increase as we open up travel and trade, so we will be very reliant on protection from vaccines and public health policy.

4. Virus variants may mean vaccination is less effective

   It is entirely predictable that viruses mutate as they replicate and infect new individuals. Mutations are random and most have no effect on the virus, or its effect on us. However, very rarely there will be mutations that help the virus to spread more easily, or which may cause more severe symptoms. The more infections, the more chance there is for unlucky mutations to emerge and this has already happened with virus variants that emerged in the UK, South Africa, Brazil and California. These variants have spread more rapidly than the initial form of the virus and some appear to be more resistant to immunity induced by the vaccines. There are worrying examples where these variants have reinfected people who have previously recovered from COVID-19, so we cannot assume that vaccination will provide us with complete protection. It is inevitable more variants will emerge and so it is imperative we detect and control them early.

5. Winter is coming

   Respiratory viruses like COVID-19 spread best in winter. This is partly because viruses survive better when the air is cool and humidity is low, but winter also tends to see people congregate inside where the ventilation is poor (relative to outside) and there are other people in close proximity. This has likely contributed to Australia’s low infection rate in summer months, and to the spikes in infection seen in the northern hemisphere winter. We should expect to see infections fall in those countries as they move into their warmer months when people can be outside, but the risk for Australia grows as our own weather conditions become more favourable for virus spread.

6. We’re all relaxing!

The rules surrounding COVID-19 are relaxed and even the few that remain aren’t being followed by many people. Are you putting on a mask when you’re within 1.5m of people? No? Neither are most other people. The problem then is that if there is an outbreak now, we have very few defences in place to protect ourselves. As our lives are now returning to close to what they were like pre-pandemic, without precautions, we are almost as susceptible now as we were then. We are now very reliant on the vaccines and on a rapid detection of COVID cases by public health officials to identify and isolate infected individuals before the virus spreads.

So what should we do?

It is entirely appropriate to be living under far more relaxed conditions now than when there were higher levels of community spread. We shouldn’t fool ourselves though. There is still a considerable risk to most of us as individuals from COVID-19 and there is a definite risk to our community.

It therefore makes good sense to take basic precautions that don’t interfere with our way of life too much, so we enjoy the benefits of our success against COVID-19, but also ensure that we protect ourselves against the threat of new outbreaks.

Easy precautions are to avoid gathering with other people in poorly ventilated areas (e.g. plan outdoor rather than indoor gatherings) where social distancing is difficult. Use hand disinfectant. Carry a mask for the rare times you may need it. Most importantly though, get vaccinated when you have the opportunity and get tested for COVID-19 whenever you have the slightest symptom of a cold.

We are reliant on effective public health policies and responses to protect us from community spread of COVID-19, but they can only provide that protection once they know an infection exists and can take action to contain the spread. Nobody expects to get COVID-19 now, but don’t take a risk with everyone’s wellbeing. If you’re slightly ill, book a test and stay home until you get your results. Once you know for sure you’re negative, you can resume normal life, but don’t be the person who assumed they just had a cold, didn’t get tested and started a new outbreak.

It’s reasonable to be confident that we won’t see large outbreaks of COVID-19 in Australia and we should all be comfortable with the relaxed restrictions that have come with our low infection rate. However, the world has changed and we need to be careful we don’t ignore the risks that COVID-19 still represents.

Professor Stuart Berzins is Professor of Immunology in the School of Science, Psychology and Sport. He leads a group that studies the regulation of human immune responses in cancer and other settings in collaboration with clinicians and research groups from other scientific institutes.

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AstraZeneca vaccine – should we pause the rollout?