It's hard to imagine right now, in a world wracked by the ongoing crisis of the COVID-19 pandemic, that something equally bad or even worse than the coronavirus might await us in our future. But it's possible, even probable, scientists say.

Long before the first cases of COVID-19 were reported and the dangers of SARS-CoV-2 were known, scientists were aware a deadly outbreak of something unknown could be lurking on the horizon, with failure to adequately prepare for it meaning a death toll likely in the millions could result.

The vision was bleak, but nonetheless faultlessly prescient: COVID-19 was effectively everything scientists said it would be. After humanity's reckless, endless incursions into nature, exposing us ever more closely to the pathogens that exist within animals, something like this was perhaps inevitable, even though the precise origins of SARS-CoV-2 remain unclear.

The shocking thing, though, is that nothing has actually changed in all this.

Despite COVID-19's emergence, we are still vulnerable to as-yet-unseen viral mutations SARS-CoV-2 might adopt – let alone whatever the next unknown future pandemic may be – and it's imperative we begin researching and preparing vaccines now that could help defend us from such threats, researchers say.

In a new commentary published in Nature, scientists from Scripps Research in San Diego, California, argue that governments and the private sector need to begin investing now in the research and development of broadly neutralizing antibodies: protective proteins that are effective against multiple strains of a virus.

"Such antibodies could be used as first-line drugs to prevent or treat viruses in a given family, including new lineages or strains that have not yet emerged," co-authors Dennis Burton and Eric Topol explain.

"More importantly, they could be used to design vaccines against many members of a given family of viruses."

Effectively, the researchers emphasize, we were lucky with COVID-19 – which isn't something people tend to say very often. The reason was SARS-CoV–2's spike protein: a convenient feature of the viral particle's molecular architecture that just happens to make vaccine design easier.

We might not be so lucky next time, however.

"The next pathogen to emerge might be less accommodating," the researchers write.

"A vaccine could take much longer to make. Even SARS-CoV-2 could be becoming more problematic for vaccines, because of the emergence of new variants."

One way to get ahead of this would be to develop pan-virus vaccines, designed around broadly neutralising antibodies that could individually target priority viruses, including potentially SARS-CoV–2 variants, HIV, influenza subtypes, Ebola, MERs, and others.

While isolating these antibodies isn't easy – taking both significant amounts of time and money to do – the outlay is incomparable to the cost of not acting, the researchers say: to reach phase I trials, investment per virus might be US$100 million to $200 million over several years, against the trillions of dollars of damage done by a pandemic like COVID-19.

"Unlike a reactive programme that swings into action when a new pathogen appears, our proposal has goals that can be described now and projects that could begin on a large scale immediately," the authors explain.

"We will have outbreaks in the future, and are very likely to see further epidemics. We must stop these becoming pandemics."

The commentary is published in Nature.