As the first data on the new Delta variant of Sars-CoV-2 began to trickle through in April and early May, Martin McKee was immediately convinced that a third wave of Covid-19 was imminent.

McKee, a professor of European public health at the London School of Hygiene and Tropical Medicine, was particularly shocked when he saw estimates of Delta’s R number, the average number of people that one infected person will go on to infect with the virus. “You could see this was a much more transmissible variant,” says McKee. On June 16, Public Health England’s strategic Covid-19 response director told MPs that if the new variant was left to spread uninhibited, its R number could be between five and seven.

For McKee, it seemed inevitable that new cases of Covid-19 – which had been steadily declining since early January – would begin to rise again. On June 24, the number of daily infections in the UK crossed 16,000, levels not seen since early February when the UK was still in full lockdown.

But the third wave will look very different to the last two. While the Delta variant is considered to be more virulent than any that have previously followed, the UK’s successful vaccination campaign appears to have broken the seemingly inevitable link between cases, hospitalisations, and fatalities. The current hospitalisation rate remains low. There were 182 new hospital admissions on June 22 – a rate of 16 per 1000 new cases – compared with 3,812 admissions on January 12, the height of the second wave, a rate of 84 per 1000 new cases.

Boris Johnson’s government is currently intending to end all restriction measures on July 19, but exactly what this will mean for new cases of Covid-19, and public health, is almost impossible to predict, due to the varying degrees of immunity to the virus in the population.

“The third wave will be different in characteristics to before, but the situation is so complex to model,” says Ravi Gupta, professor of clinical microbiology at the University of Cambridge. “You have lots of vaccinated people, those who are semi-immune because they’ve already been infected, unvaccinated people, and a lot of young people.”

In addition, intensive care wards report a very fragmented picture across the UK, making it far more difficult for policymakers to form a coherent strategy. While the third wave has already intensified in the North West, where there have been 17,496 new cases over the last seven days, other regions are still seeing relatively little transmission. “Where we are, it’s fine,” says Matt Morgan, consultant in intensive care medicine at University Hospital of Wales. “Wales is doing really well. But in some areas in the North and the West Midlands, you can see this scooped out curve of hospital numbers climbing which is the big concern.”

Morgan thinks that this variation between regions is making it hard for the public, mentally fatigued by the toll of repeated lockdowns, to accept the potential threat posed by the third wave. “Waves one and two were a case of, ‘We're all in it together,’ to some extent,” he says. “It’s not like that now, and it’s really hard for people to get the narrative that the vaccination campaign has gone so well, yet there’s still an ongoing risk.”

While the NHS continues to vaccinate the population with remarkable efficiency – as of June 22, 64 per cent of the country had received at least one dose of the vaccine – there remains a proportion of people who are not protected. Martin Landray, a professor of medicine and epidemiology at the University of Oxford, points out that there will be a percentage of elderly individuals who have not mounted a full immune response to the vaccine, while the effects may begin to wear off in others who received the jab in the early months of the campaign.

Last week, Nadhim Zahawi, minister for Covid vaccine deployment, said that nine out of ten people eligible for a vaccine had accepted one. However Landray points out that this still means that one tenth of those who should have received the jab remain unvaccinated. “Either they didn't want it, didn’t turn up, or they couldn’t have it for some sort of medical reason. Everyone thinks that the older age groups are covered, but we will still have some problems with unvaccinated people,” he says.

Landray fears that if case numbers continue to climb, the virus will eventually reach those vulnerable individuals in the months to come, potentially causing a new spike in hospitalisations. One of the problems is that people who have been fully vaccinated may still be capable of transmitting the Delta variant to some extent. Gupta points to a study of Indian healthcare workers, which showed that even people who had received two vaccine doses were still contributing to transmission chains within hospitals, fueling the pandemic.

As a result, McKee believes the government needs to look at vaccinating teenagers as a way of mitigating the threat of the third wave to the old and vulnerable. “This needs to happen at the absolute minimum,” says McKee. “The Joint Committee on Vaccination and Immunisation is looking very much at the risks and benefits to children themselves, but we have a long tradition in countries of vaccinating people for the wider benefit. We vaccinate children against influenza partly because we don’t want them to get it, but primarily because we don’t want them to infect their grandparents.”

A lot has changed since the first wave of the pandemics. Doctors do have an array of new options at their disposal to fight the virus. Over the past year, the UK’s groundbreaking RECOVERY Trial – a program which launched in March 2020 enrolling tens of thousands of patients at dozens of hospitals for clinical trials investigating Covid-19 therapies – has provided vital information on treatments which work, and those that do not. Morgan says that the latter information is just as important, as it has helped streamline care pathways on wards and in intensive care.

As a result, convalescent plasma, hydroxychloroquine, aspirin, colchicine, and azithromycin have all been ruled out. But dexamethasone, tocilizumab, and monoclonal antibodies – artificial antibodies which can be administered to elderly or immunosuppressed patients who cannot mount an immune response against the virus, via an intravenous drip – have been shown to be effective life-saving therapies.

Dexamethasone and tocilizumab, both help to dampen  the deadly cytokine storm which has been widely touted as the driving force behind many of the fatalities from Covid-19. The latter treatment has only been available from December 2020, while various monoclonal antibody therapies have been newly approved in recent weeks as a result of new data from the RECOVERY study.

At the same time, the information we now have about some of the longer term impacts of the virus, especially Long Covid which has impacted younger, previously healthy women particularly hard, means that the risk posed by the third wave cannot only be assessed in terms of hospitalisations and deaths.

Accumulating evidence now shows that SarS-CoV-2 can persist in the brain as a chronic infection, causing structural changes, and inducing a higher risk of strokes, muscle disorders, dementia, and psychiatric disorders, even among non-hospitalised patients.

The third wave will almost certainly look very different to before. There will inevitably be fatalities, but not of the levels of the previous two waves. As a result, some doctors feel that any decisions on re-implementing restrictions in the months to come are likely to be moral and ethical questions, rather than medical necessity.

“I think wave one, wave two, it was clear that there was a huge emerging wave of infections and hospitalisations and deaths,” says Morgan. “Now, it’s different. I don’t think these are medical decisions anymore, they are ethical, moral and societal decisions, and they have to be answered by society, governments, and ethical institutions.”

• 🖥️  Sign-up to WIRED’s business briefing: Get Work Smarter
• The mRNA vaccine revolution is just beginning
• Facebook’s content moderators are fighting back
• Companies are finally getting rid of dumb work perks
• China has triggered a bitcoin mining exodus
• Why Apple is betting big on spatial audio
• It’s time to ditch Chrome
• 🔊 Subscribe to the WIRED Podcast. New episodes every Friday

This article was originally published by WIRED UK