Zero Covid—known unknowns

On 11 March 2021, The BMJ hosted a webinar on zero covid. An expert panel explored what zero covid means, whether it is even possible, the different routes and paths countries are taking to manage the pandemic, and possible futures. Nikki Nabavi and Juliet Dobson report

The webinar was inspired by an editorial published in The BMJ entitled “Covid-19’s known unknowns.” The key message: “The more certain someone is about covid-19, the less you should trust them.” Register for future events here

“There should be a compelling case that eradication is better than simply ongoing control”

Art Reingold, UC Berkeley, discussed different strategies for infectious disease control. He began by defining the key terms such as control (reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts; continued intervention measures are required to maintain the reduction), elimination (reduction to zero of the incidence of a specified disease in a defined geographic area as a result of deliberate efforts; continued intervention and control measures are required  to prevent re establishment of transmission), eradication (permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer needed) and extinction (where the infectious agent no longer exists in the laboratory). “Most people now use [the terms] elimination and eradication interchangeably”, he added. 

Reingold went on to demonstrate that diseases such as polio, measles, and rubella had all been eradicated, whereas rabies has been eliminated, and smallpox is extinct, while tetanus and cholera are still only controlled. 

He then explained that “we have to consider the various epidemiologic features of the disease, whether they’re non-human reservoirs, how easily it spreads, and naturally induced immunity. We need to take cognisance of the interventions that are available, the effective interventions, and to preferably know that elimination in a particular area was feasible before deciding to move to the eradication.”

“It’s also important to have a political will and support of the population, that someone will pay the costs of eradication,” he added. “I want to ask the question what does Zero Covid mean? Does it mean a global absence of covid-19 cases in humans? Does it mean a global absence of SARS-CoV-2 transmission between humans? Does it mean a global absence of SARS-CoV-2 virus or does it mean something else?”

For and against

Deepti Gurdasani, Queen Mary’s University London, argued that zero covid is one of the only “known knowns in this really uncertain and dire pandemic”, and explained that her idea of zero covid is getting levels down to “zero or near zero in the community, in a way where it can then be contained within that region with active surveillance and rapid response, as and when cases arise.”

Gurdasani acknowledged the scientific discourse that says zero covid is unachievable, because eradication for most infectious diseases has not been achieved, and said that many think it is not worth striving for. “But I’d argue that ultimately trying is much better than not trying at all. Even if we don’t manage to achieve elimination, we will still protect our economy and society much better than if we hadn’t tried at all.”

“Zero covid is not the fringe or an exception, it has been achieved in 30 countries, with 15 more countries close to achieving it,” she added. “It is clear that the countries that have aimed for or achieved zero covid have had far fewer deaths…[but also] had the least hit to the economy.”

John Ioannidis, Stanford, stated that while he would wish for zero covid in the same way that he would wish for “zero cancer or zero starvation”, he still questioned whether we can achieve this, and if our efforts may end up increasing overall deaths and the burden of total (non-covid related) disease. He also argued that social inequalities such as racism and poverty, combined with other modifiable risk factors such as obesity have been responsible for and have “really caused” such a high number of covid deaths.

Master of ceremonies, Phil Hammond, asked the panel whether the countries who better managed health inequalities had subsequently been better at managing SARS-CoV-2, which both Christina Pagel, UCL, and George Davey Smith, University of Bristol agreed with.

Country case studies 

New Zealand case study

Michael Baker, University of Otago, described how in New Zealand they took, “three broad approaches: exclusion of cases with good border management; good systems of case testing and contact tracing; and then a range of approaches for reducing transmission in the community. And of course, vaccination just adds another tool for reducing community transmission.”

“We have found that having an explicit zero covid goal has been very motivating.” Regarding the tensions between GDP vs mortality, Baker said that “it’s a false dichotomy that you’re trading off one against the other. Certainly the New Zealand experience, and I think of many other countries pursuing elimination, is that we save lives. And also the economy has performed very much better…elimination should be the default option for future pandemics.”

Norway case study

Camilla Stoltenberg, Norwegian Institute of Public Health, discussed Norway’s experience saying: “Core to Norway’s strategy has been the extensive use of testing, isolation, tracing, and quarantine to contain local outbreaks”

She said that there have been two critical aspects. One is the use of digital contact tracing tools, “We started at a very early stage to develop such a tool, but did not succeed in the first place…the privacy implications of these tools exceeded what would have been allowed under current current regulations…So the use of the digital tool now is voluntary. Neither can public authorities such as the Norwegian Institute of Public Health access this information, so we cannot use it for surveillance purposes.”

The other critical aspect is border controls. “Norwegian quarantine rules, which have included the use of quarantine hotels for non-residents from early November, have been amongst the strictest in Europe since 20 January.”

But she also highlighted some issues with strict border controls: “geography, economic interests and connectivity, and the rights and freedom of our own inhabitants.” 

Korea/ Japan/ Taiwan case study

Chang-yup Kim, Seoul National University, said that all three countries have done well in terms of death rates, cases, and the economy.

“One of the key characteristics is the role of the government in this kind of public health problem. The coordinating mechanism, the centralised and the leading and coordinating role of the central government has been functioning,” he said. 

Canada case study

Stefan Baral, John Hopkins Bloomberg School of Public Health, talked about the outcomes of restrictions based covid-19 strategies in Ontario, Canada. He talked about structural racism as a baseline driver of disparities and covid-19, and asked what would it mean to achieve equity and impact in the covid-19 response? 

Baral presented data from the United States which “show that historical segregation and structural racism are hugely predictive of where cases have been. But in the least diverse areas, you’ve seen the least amount of diagnoses and associated mortality and in the most diverse areas you’ve seen the most.”

“The second thing that structural racism obviously plays out is in terms of working conditions. And so this idea of essential worker status has been critical,” he said.

Baral concluded that, “What we’ve seen is that unless we actually resource the lower income areas and more economically marginalised areas and more racialized communities to be able to decrease their contact rates in an equitable way, we’re going to continue to see this prevention gap that if we treat it as like an all lives matter response and we do not pay attention to the particular vulnerabilities of particular communities and we don’t resource them in order to address those risks, we will see this prevention gap where everybody’s more affected by it.”

Zero covid: implications for childhood vaccination

Jennie Lavine, Emory University, said that one of the key things that they have been focussing on is, “how does immunity get developed and then how does it wane and how does that affect transmission and disease separately?”

“Our best guess is that there is a short period following a primary infection or a vaccination when reinfection is unlikely. And this is thought to be maybe a year, maybe not even. And there’s a number of different studies from these different viruses suggesting that. And then people do get reinfected,” she said. 

“So an initial infection or hopefully also an initial vaccination leads to short term transmission reduction, but long term disease reduction…It makes sense that we can locally eradicate measles because vaccination in childhood provides this very strong protection. But when we look at SARS-CoV-2, it’s a very different story,” she said.

Possible futures for the UK 

On the possible futures for the UK, Christina Pagel, UCL, highlighted how hard it is to predict this at present: “So I’m really talking about two possible futures…And I’m talking about this year because I think the future is so uncertain that we just don’t know what’s going to happen.”

At the moment she said that there is an optimistic future for the UK, with cases falling and vaccination high. “But I think that a strategy that aims for zero covid aims for community transmission or minimal community transmission for this year makes this future so much more likely.” 

On schools Pagel said, “This is a risk that we are now going to start cases increasing again when actually the large majority of people under 50 have not been vaccinated…But at the heart of all of these measures is its control of community transmission…we do know that wherever community transmission is very low, schools are pretty safe, that you can keep them open, that very few children ever have to go home and isolate. Keeping that community transmission low is the way to keep schools open.”

Commenting on the UK’s vaccination strategy Pagel said, “This is an increased risk when millions of people, as they are in the UK, are partially vaccinated because we’re doing it delayed secondary strategy. I happen to think this was the right strategy given where we were in January. However, there is that risk that when you only have one dose, it might be slightly easier for mutation to evade the vaccine. And a zero covid approach this year is the best way to reduce this possibility.”

Pagel also echoed Baral’s points about deprivation and covid-19, saying, “Deprivation is a big, big driver of covid and people cannot currently afford isolate. And so they don’t get tested and they don’t self isolate. And we’re seeing this in England now. The areas with high deprivation also have high pockets of cases. We’re also seeing that people aren’t getting vaccinated as much and more deprived areas, particularly in younger age groups.”

George Davey Smith, University of Bristol, looked at what we can learn from history to inform the future: 

“And we really need to know [about is] the effects of long lockdown before we’ve heard about long covid. What are the long term effects on young people who have been out of education? What are they going to pay over 20 years, 30 years? We’ve really got to think about about that. And we’ve got to realise that what’s been happening over the last year has been a massive intergenerational transfer of the harms and risks from affluent older people onto working class youth. If your kids go to private education and you can work from home during lockdowns, fine if you actually have a job. But if you have to go out, like a delivery driver who’s facilitating the lives of people working at home, then that isn’t fine and it’s not fine for your kids, and for your kids futures. So we really should think about that and how that is magnifying inequalities and inequalities in the future, not just now.” 

This webinar was part of The BMJ‘s series of covid-19 known, unknowns webinars. Find out more and register for future events here

Nikki Nabavi, editorial scholar, The BMJ

Juliet Dobson, editor, The BMJ

Competing interests: none declared.

 Strategies for ID control (Chair: Phil Hammond)

– Art Reingold (UC Berkeley)

For and against zero covid/elimination (AP) (Chair: Helen Ward)

– Deepti Gurdasani (QMUL)

– John Ioannidis (Stanford University)

Country Case studies (Chair: Allyson Pollock, Newcastle University)

– Michael Baker (University of Otago) a New Zealand case study

– Camilla Stoltenberg (Norwegian Institute of Public Health) a Norway case study

– Chang-yup Kim (Seoul National University) a Korea/ Japan/ Taiwan case study

– Stefan Baral (John Hopkins Bloomberg School of Public Health) a Canada case study

Zero covid: implications for childhood vaccination (Chair: Phil Hammond)

– Jennie Lavine (Emory University)

Possible futures for the UK (Chair: Kamran Abbasi)

– Christina Pagel (UC, London)

– George Davey Smith (University of Bristol)

Discussion/ Q&A (Chair: Phil Hammond)