Not touching your face. Panic-buying toilet roll. Disinfecting groceries. Some of the advice and behaviour of the early days of the covid-19 pandemic can, in retrospect, seem utterly bizarre. But when an unknown virus swept rapidly around the world, we were engulfed by questions – how does it spread, who is most at risk, how can I avoid catching it and just how bad is this going to get – that the instruments of medical science couldn’t immediately answer.
“None of us could comprehend the scale and broad societal impact of this, the speed at which it developed,” says , who participated in the UK government’s Scientific Advisory Group for Emergencies (SAGE) for much of the early years of the pandemic, and is now chief scientist at the World Health Organization.
But even from the very beginning of the crisis, researchers were examining every aspect of covid-19 – its biology, how to prevent and treat it, how to stop it spreading and how to manage a deadly outbreak amid the complexities of modern society. The twists and turns of the past five years have yielded many insights – and should leave us better prepared for future pandemics, if governments choose to listen.
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Flattening the curve
Initially, much of the focus was on epidemiology and statistical modelling in an effort to forecast the spread and impact of the virus. Officials in many countries started speaking of the need to “flatten the curve”. Anthony Fauci, then director of the US National Institute of Allergy and Infectious Diseases, that “if you look at the curves of outbreaks, they go big peaks, and then come down. What we need to do is flatten that down.” That, he said, “would have less people infected. That would ultimately have less deaths. You do that by trying to interfere with the natural flow of the outbreak.”
Social distancing and then lockdowns became necessary to prevent countries experiencing those big peaks of infection and death. But as graphs depicting hypothetical outbreak dynamics became commonplace on TV and social media, messages to the public became confusing and unclear.
“I think a lot of people got anchored to the idea of: we can have hospitals not overwhelmed, and we can have a single wave, and it will all be over,” says at the London School of Hygiene & Tropical Medicine, who was a member of the UK government’s pandemic modelling science advisory group. But without containing the virus, this would never have been possible, as a large majority of the population hadn’t yet been infected.
“We had all this silly discussion about whether a second wave was going to happen, and you just had to look at the amount of susceptibility,” says Kucharski. “There was never a reason that we weren’t going to have a second wave, if we still had transmission.”
In the US and UK, the infection waves of late 2020 to early 2021, after some restrictions had been lifted, had a heavy death toll. But while this should have been predictable, it wasn’t inevitable. Other countries that had made more concerted efforts to contain their outbreaks earlier on in 2020 tended to continue taking action to keep infection rates and death counts down.
, a public health researcher at the University of Edinburgh, UK, and author of Preventable, points to the strategies of Japan, South Korea, Denmark, Norway and New Zealand: “contain until you get a scientific breakthrough, and then you mass vaccinate and open up. If you look at the death rates, that really paid off.”
The vaccine gamble
But how could we know there would soon be a vaccine? When the pandemic began, vaccine development was considered “fast” if it only took four or five years. Countries that remained heavily locked down were betting that either this could be done quicker or other game-changing medical interventions would soon be developed – a bet worth taking, says Sridhar, though this view wasn’t universal at the time.
“Faith in science was probably one of the biggest disagreements at the start,” she says. “I’m quite an optimist, but also, if you look at most human afflictions over time, we have developed ways to defang them.” This hasn’t always involved vaccines – for AIDS, we now have antiretroviral drugs, for example, even if it has taken some time. “The idea that we’d have a disease and have absolutely no scientific response to it was just astonishing to me,” says Sridhar.
As the months went by, science did indeed deliver. Trials determined which drugs were best for treating covid-19 – the steroid dexamethasone, for example, was found to cut the risk of death in severe cases by up to a third, while IL-6 inhibitors were discovered to .
And we soon had the fastest vaccines ever developed, many of them based on mRNA technology that hadn’t been used in this way before. “You’d be lying if you said you weren’t surprised,” says Farrar, although he notes that “this didn’t come out of total left field” – the 2023 Nobel prize in physiology or medicine, seen as the covid-19 vaccine Nobel, was given for foundational work on mRNA conducted decades ago.
Another surprise was that, as well as reducing a person’s risk of getting infected, the vaccines also lowered their risk of transmitting the virus to others if they did still get infected. This wasn’t a given. “I think the early vaccine results were just better than anyone could have hoped for,” says Kucharski. Because they were so good against the alpha variant, they made it possible for countries like the UK to reopen after the heavy waves of late 2020 and early 2021, he says.
Covid-19 is airborne
While treatments and vaccines were a triumph, there were failures. One of the most notable is how long it took the WHO to acknowledge that covid-19 was airborne. In March 2020, the agency emphatically “FACT: #COVID19 is NOT airborne”, stating that the coronavirus is mainly transmitted through droplets when someone coughs, sneezes or speaks. The agency’s advice at that time was to keep a 1-metre distance from others, disinfect surfaces frequently, avoid touching your eyes, nose and mouth and practise good hand hygiene.
“It really wasn’t any great surprise that this virus was airborne,” says at the University of Oxford. “SARS-1 was airborne. MERS was airborne. Flu is airborne. TB is airborne. Any respiratory disease is airborne.”
Greenhalgh had been arguing from the early months of the pandemic that . But she says handwashing won out as the most evidence-backed way of preventing the spread of disease because doctors need to wash their hands to prevent spreading infections between their patients, and as a result have conducted “loads of randomised controlled trials of handwashing”. That contrasted with the state of evidence on the efficacy of mask-wearing before the pandemic, which was less extensive or accepted.
“The medical profession is a powerful profession and tends to think towards therapeutics and vaccines, and less towards social and behavioural factors,” says Farrar. “I think one of the key lessons that we must all learn is the critical importance of behavioural, social and non-pharmacological interventions, including masks and social distancing, ventilation and opening windows.”
As the pandemic progressed, the WHO began recommending mask wearing and ventilation alongside its original advice, but it wasn’t until late 2021, when the omicron variant was spreading rapidly, that the agency introduced the phrase “airborne spread” to its public communications.
“Throughout the pandemic and in all its work, WHO has reviewed evidence, consulted a broad range of experts and adapted its guidance with the evolving science,” says a WHO spokesperson, noting that one issue had been differences in terminology used by different fields. In April 2024, the agency introduced updated definitions of phrases such as “through the air” and “airborne transmission”.
Would we lock down again?
Hopefully, better agreement about scientific terminology will help when the next pandemic hits, but what about one of the most contentious interventions in the virus-fighting arsenal – lockdowns?
Media reports now commonly suggest that people would never lock down because of an illness again, but at University College London disagrees. “We probably would if people were dying in the streets,” she says, or if children were badly affected or the symptoms were as nasty as Ebola, for example.
This pessimism about people’s willingness to make sacrifices echoes speculation in the early days of the pandemic that people wouldn’t tolerate too many restrictions for too long – the UK government talked of “behavioural fatigue”, despite behavioural scientists at the time pushing back on the concept.
“I think it’s really important that the lesson is learned that you don’t start off with an assumption that people don’t understand and they don’t sacrifice themselves, and they don’t look after each other or do really difficult things, because they do,” says , a health psychologist who chairs the WHO’s behavioural science advisory group and has also served on UK government advisory groups. “Whatever the crisis, you see people really pulling together and looking after each other. A collective solidarity builds in. This is seen in so many different types of disasters, in so many different places.”
Michie argues “if there’s trusted leadership, if there’s clear communication as to what the benefits are for yourself, your loved ones, your communities and services, and the negative consequences of not doing it, people will rally.” But she notes that people need to be helped to do so – different countries provided differing levels of state support for people who had covid-19 and needed to self-isolate, for example, which may have led to people continuing to work while infected as they had no other choice.
But it may be possible to avoid lockdowns in a future pandemic, says Sridhar. “Countries that were reluctant to implement measures ended up in harsher cycles,” she says, veering from not reacting to the virus to putting in place strict lockdowns and going back and forth again. Conversely, governments that better controlled the virus – like those of Japan and New Zealand – were more consistent in their messaging around trying not to catch the virus and having faith that scientific solutions would follow.
Farrar says there is no doubt we are better prepared for the next pandemic. “We’ve understood the importance of genomic surveillance much better than we’ve ever understood it before. The diagnostics and surveillance around the world needs to be sustained, but is in a much better place than it was in 2019.” But he is concerned that there are gaps in our preparedness, especially when it comes to effective interventions like drugs and vaccines for threats such as a possible flu pandemic.
“I think we have a real vulnerability around therapeutics and indeed vaccines for things we know about, let alone for things we don’t know about,” says Farrar. “And as interest in the pandemic wanes, then my concern is the interest in making sure we close that gap will also wane.”
Read more in our special report about the five years since covid-19
