A central tool in the armory of many nations in their response to the coronavirus pandemic has been the immunity people are believed to develop after they’re exposed to the virus.  The hope is that enough people will safely contract the virus, and therefore develop immunity, so that the economy can thus re-open after the enforced lockdown.

It’s a controversial theory, not least because it exposes a great many vulnerable people to the virus.  Nonetheless, advocates argue that the number of those who have recovered from the virus is as important as the number of those who have died from it.

Despite the controversy, it’s an approach that new research from Georgia Institute of Technology suggests may have some merit.  The researchers developed a model that suggests a strategy of herd immunity can lower the risk associated with allowing higher levels of human interaction.

“Our model describes ways in which serological tests used to identify individuals who have been infected by and recovered from COVID-19 could help both reduce future transmission and foster increased economic engagement,” the researchers say. “The idea is to think in advance about how identifying recovered individuals could help serve the collective good, using information collected on neutralizing antibodies in new ways.”

Herd immunity

The model predicts that in a population of 10 million people, an intermediate herd immunity strategy could see deaths fall from 71,000 to 58,000, with an enhanced strategy cutting the deaths down to just 20,000.

Suffice to say, the testing for those with protective antibodies is nowhere near at sufficient scale to provide countries with accurate insight into how many people have been infected over the past few months.  Nonetheless, the researchers believe that targeted use of such tests, even those that are not entirely reliable, can help to increase positive predictive values.

“We want to think about serology as an intervention,” the researchers say. “Finding out who is immune to the coronavirus could make a big difference in trying to reduce the risk to people who would be vulnerable by interacting with someone who could pass on the disease.”

The researchers propose that such serological testing begin with healthcare workers, as their likelihood of infection is going to be higher.  They believe it can spread out from there, however, and the numbers of asymptomatic cases over the past few months will dwarf the numbers we know about.

“There may be a deeper pool of individuals who can help within their own fields and other fields of specialization to reduce transmission,” they continue. “The reality is that people within high-contact jobs probably are likely to have a higher incidence of infection than other groups.”

Practical challenges

Of course, as established in a recent article, there are numerous challenges involved in identifying immunity, and indeed providing people with an ‘immunity passport’.  Researchers argue that immunity passports will inevitably create artificial restrictions on who can and cannot participate in various social and economic activities.  In a perverse sense, it may encourage people to become infected so that they can return to their normal activities.

The team from the Georgia Institute of Technology also highlight potential privacy issues, and believe that individuals will need to make informed decisions regarding the risks involved so that the greater good of society can be achieved.

“What this model says is that if we could identify individuals who are immune, there is a chance that some individuals would not have to reduce their level of interaction with others because that interaction would be less risky,” they say. “Rather than trying to keep reducing interactions, which is helpful for reducing transmission but bad for what it does for the economy, we might be able to maintain interactions while reducing the risk, combined with other mitigation approaches.”

Obviously, the development of a vaccine is the ultimate exit point from the virus, but until then, it’s likely that some form of herd immunity strategy will be required.