Across the mat, prominent Harvard epidemiologist Marc Lipsitch punched back with a defiant response titled: «We know enough now to act decisively against COVID-19.»

Watching from the sidelines? Everybody else. The people who worry the world has gone too far too fast.

And those afraid the response hasn’t come fast enough.

The debate comes down to questions about data. What is the true fatality rate of COVID-19? How many people are already infected?

«Better information is needed to guide decisions and actions of monumental significance and to monitor their impact,» Ioannidis wrote. «In the absence of data, prepare-for-the-worst reasoning leads to extreme measures of social distancing and lockdowns. Unfortunately,we do not know if these measures work.»

Ioannidis told CBC News he worries about the consequences of those measures.

«Put a stall to the entire economy. Tell people to stay at their homes, get depressed, commit suicide, domestic violence. Who knows? Child abuse, children losing their education, companies crashing … unemployment, the stock market already dropping 20 per cent.

«Is that the solution?»

The day after Ioannidis’s bombshell commentary appeared on the medical news website STAT, the site published Marc Lipsitch’s response.

Lipsitch said he talked to Ioannidis beforehand and found that they had more in common than it seemed.

«I would say that his article did what contrarian writing should do: started a discussion.»

Lipsitch insists drastic action is required.

«Waiting and hoping for a miracle as health systems are overrun by COVID-19 is not an option,» he wrote. «For the short term, there is no choice but to use the time we are buying with social distancing to mobilize a massive political, economic, and societal effort to find new ways to cope with this virus.»

Social media lit up as other leading scientists joined the fray.

Dr. Gabriel Leung, dean of medicine at the University of Hong Kong, who has seen COVID-19 up close, challenged how Ioannidis compared the illness to the seasonal flu.

Swiss epidemiologist Marcel Salathé responded with a satirical post using an image of the 1918 flu pandemic.

‘Pandemic of emails’

For his part, Ioannidis is at home in Palo Alto, Calif., obeying an order by county officials in the San Francisco area to «shelter in place.» He’s also weathering another storm — «a pandemic of emails» flooding his inbox as people respond to his commentary.

«The vast majority,» he said, «are congratulations and thinking along the same wavelength.»

He said he doesn’t know what response would be appropriate. And he acknowledges the situation in northern Italy is a disaster.

But he urges scientists and decision-makers to make it a priority to gather the data to find out if the response to the virus might end up being more damaging than the pandemic itself.

Prof. Ross Upshur of the University of Toronto is a public health expert, a physician and a scholar of the ethics and history of global health emergencies. He’s also a veteran of the SARS outbreak.

He has corresponded with Ioannidis over the years and respects the Stanford professor’s expertise: «He is one of the most cited, most highly regarded researchers.»

But in this particular case, Upshur said, Ioannidis is making an error in his analysis by failing to view the current response through the lens of public health instead of evidence-based medicine.

«Of course there’s a lack of data,» said Upshur. «It’s all nice to stand on the sidelines and say, ‘Hey, you know we don’t have very good data. These are not evidence-based decisions.’ Well, of course they’re not, because we don’t have the evidence.»

Ioannidis said it’s time to make getting that data a top priority. The capacity to do the necessary research exists, even in the midst of the pandemic response, he said.

«These data may show that lockdown is something that we need to do and then decide for how long,» he said. «They may show that it is a horrible idea. Because we don’t know what harms these interventions will have.»

He said the response so far has been based on modelling, which uses a series of assumptions about important factors including the rate of infection and the case fatality rate.

So far, COVID-19 has killed almost 9,000 people around the world. Doctors working in modern health-care systems in Italy, France and Spain report being on the verge of collapse.

Don’t try to be perfect. Be fast

Dr. Mike Ryan, head of the World Health Organization’s emergencies program and a veteran of the Ebola epidemic, said «speed trumps perfection.»

«Perfection is the enemy of the good when it comes to emergency management,» he said during the WHO’s briefing last Friday. «Everyone is afraid of making a mistake. Everyone is afraid of the consequence of error. But the greatest error is not to move. The greatest error is to be paralyzed by the fear of failure.»

Still, Ioannidis said he worries about a domino effect with the global response.

«I think there is … the feeling that other leaders have taken measures, and if we don’t act, there is a sense of negligence. Doing that without a plan to realize where we are and where we’re headed is extremely dangerous.»

‘Spring of Fear’

The roadmap for responding to public health emergencies was drawn centuries ago, according to Ross Upshur. There are massive volumes of research, philosophy, court decisions and public inquiries that have upheld the legal and ethical imperative to take dramatic action to protect against a dire threat to public health, he said.

The touchstone is the precautionary principle, clearly articulated in the 2006 investigation into Canada’s response to the SARS epidemic, written by Justice Archie Campbell of the Ontario Superior Court.

«Where there is reasonable evidence of an impending threat to public health, it is inappropriate to require proof of causation beyond a reasonable doubt before taking steps to avert the threat,» Campbell wrote in a chapter called «Spring of Fear,» citing Justice Horace Krever, who presided over Canada’s tainted blood inquiry.

As Upshur put it: «We have put in place public health laws and public health powers for a reason.»

«I know there is going to be a reckoning,» he said. «I know people are going to ask whether this decision was disproportionate or not. But I don’t think people in public health had any other option.»

Ioannidis said that might be true. But there are some key questions that need to be answered in order to make sound decisions going forward, he said.

«We desperately need to know, No. 1, the prevalence of infection, and No. 2, the incidence of new infections,» he said. «If we make decisions with such tremendous uncertainty, we can get tremendous harms.»

The lack of data is one point on which Lipsitch and Ioannidis agree.

«The U.S. has done fewer tests per capita so far than almost any rich country in the world,» Lipsitch wrote. «And many critical details of the epidemiology — including the absolute number of cases, the role of children in transmission, the role of presymptomatic transmission, and the risk of dying from infection with SARS-CoV-2 — remain uncertain.»