Zoë Hyde from UWA believes it is better to overreact than do too little with a variant that is more transmissible and more virulent. This article was originally published in The Guardian.

Australia’s pandemic response has been the envy of the world, but the emergence of the Delta variant of the novel coronavirus has put that at risk. 

The Delta variant is more transmissible than the original strain of the virus and is more likely to cause severe illness.

This means there’s a higher risk of the virus escaping hotel quarantine, and that it will be more difficult to stamp out if it gets into the community. It also means that younger people are now more at risk of getting sick.

However, it’s still possible to control the virus, but we’re going to have to change our strategy. 

The first sign of trouble for the world came in late March, when there was a sudden uptick in new Covid-19 cases in India. Over little more than a month, infections rose from about 20,000 daily cases to more than 400,000 a day. Stories of overwhelmed hospitals and crematoriums made headlines worldwide.

Experts were puzzled by the surge. Some thought the premature relaxation of restrictions was responsible, with large crowds at religious festivals and political rallies providing fertile ground for the virus to spread. But others suspected an additional factor: new variants.

We now know that a new lineage of the coronavirus – B.1.617 – played a key role in what happened in India. There are two key variants in the B.1.617 lineage, which the World Health Organisation has named Kappa (B.1.617.1) and Delta (B.1.617.2). Victoria recently beat an outbreak of the Kappa variant, although it had a few Delta cases as well. New South Wales is now facing an outbreak of the Delta variant.

We don’t know much about the Kappa variant, but it appears to be at least as transmissible as the Alpha variant that emerged in the United Kingdom, and probably has a small transmission advantage over it. In contrast, the Delta variant appears to be at least 40 per cent more contagious than the Alpha variant, and at least 80 per cent more likely to put people in hospital.

In simple terms, this means the average person infected with the Delta variant is likely to transmit it to about six other people. That compares with about four for the Alpha variant, and roughly 2.5 for the original strain of the virus. It’s important to remember these figures are averages. A key feature of Covid-19 is super-spreading. Most people infected with the virus don’t seem to pass it on.

Unfortunately, the remainder can infect anywhere from a single person to dozens of people.

We’ll likely need to vaccinate more than 80 per cent of the entire population – including children

It’s this dramatic increase in contagiousness that makes the Delta variant so dangerous. In just a couple of months, the Delta variant has become dominant in England and now  per cent of new cases. In the US, the proportion of Delta cases has doubled every fortnight, reaching 20 per cent this past week.

In Europe, it’s forecast that 90% of new infections will be Delta cases by the end of August. Even Israel, which some thought might have reached herd immunity after vaccinating 80% of adults, is facing a new outbreak of the Delta variant. The lessons are clear. High rates of vaccination in adults aren’t sufficient to contain the Delta variant.

We’ll likely need to vaccinate more than 80% of the entire population – including children and adolescents – before we’re safe from outbreaks. At the moment, only about 5% of Australia’s population is fully vaccinated.

Fortunately, vaccines continue to work against the Delta variant. Preliminary data from the UK suggest the Pfizer vaccine is 88% effective against symptomatic infection. The AstraZeneca vaccine offers 60% protection against symptoms.

However, both of these vaccines appear to offer more than 90% protection against hospitalisation, although the second dose is crucial for maximum protection. 

We all need the protection that vaccination brings, because new variants – such as Delta – have changed who’s at risk. A person in their 20s or 30s who gets infected with a variant has a similar chance of ending up in hospital as someone in their 40s or 50s who got infected with the original strain.

We also know that about one in seven people who get infected will develop long Covid. The UK’s Office for National Statistics estimates that more than one million people are now living with the condition, and the National Health Service has had to set up 15 new clinics to treat long Covid in children.

These are outcomes we want to avoid in Australia, and we can – but only if we act decisively. 

We should require masks in public places at the first sign of an outbreak. It’s now compulsory to wear a face mask in Greater Sydney and surrounding regions, but this measure was introduced relatively late. Last week the NSW government recommended their use, but stopped short of mandating them. 

Unfortunately, we know that voluntary mask policies lead to insufficient compliance, and this puts the whole community at risk. We need to take rapid action to prevent the virus from spreading in the community. This is the best way to avoid a lockdown.

However, when mystery cases are detected in the community, short “circuit-breaker” lockdowns must be seriously considered. This gives contact tracers a much-needed chance to get ahead of the virus. 

The Delta variant spreads much quicker than previous strains, so we need to act faster than we have in the past. A little more than one week after the first case was detected, inner Sydney went into lockdown, with Greater Sydney following a day later. But experts, including the Australian Medical Association, had called for a tougher and more rapid response. 

There’s no margin for error with the Delta variant, and it’s better to risk overreacting than do too little.

Lockdowns deliver the best results when they are applied early, and when they are very stringent. Going “hard and fast” has the best chance of stamping out the virus quickly, and leads to a quicker economic recovery. Victoria learned the hard way that it takes a long time to get back to normal if the virus has built up momentum. We shouldn’t risk the chance of needing prolonged lockdowns by not doing enough in the early stages of an outbreak.

Although some may feel these measures are heavy-handed, Australia’s pandemic response has actually delivered better outcomes for health, the economy, and civil liberties than countries that have tolerated some transmission.

We also need to address the elephant in the room that’s led to the latest outbreaks.

Unless we take steps to prevent airborne transmission, we’re going to struggle to contain the Delta variant. The virus that causes Covid-19 is frequently spread by the airborne route. This means that it moves through the air like cigarette smoke, and can linger in an enclosed space after an infectious person has left. That’s why ventilation is key to reducing the risk of transmission.

To protect ourselves, we need to increase the amount of fresh air in indoor spaces and also equip our healthcare workers and quarantine staff with P2/N95 masks. Loose-fitting surgical masks won’t fully protect them from the Delta variant, and that places the rest of the community at risk too.

At least one in every 191 cases in hotel quarantine leads to infections in the community, which is an unacceptable level of risk given the consequences. But we could almost certainly prevent the majority of outbreaks if we followed recommendations recently published in the Medical Journal of Australia. We also need to step up precautions in our schools, which have been a common site of Delta outbreaks in the UK.

Australians should be proud of the way we’ve handled the pandemic so far. We’ve largely avoided the devastating surges that have battered nations overseas, and even Melbourne’s second wave was an important learning experience.

It showed how quickly the situation can deteriorate if we don’t act swiftly, but it also showed we can eliminate the virus if we try. The emergence of the Delta variant has made this task more difficult.

However, if we adjust our strategy to take airborne transmission into account, and plug the gaps in our quarantine system, that will buy us the time we need to vaccinate Australia, which is our ultimate ticket out of the pandemic.