As countries scramble to stem the spread of COVID-19, the debate over 'immunity passports' is gathering steam with some governments pushing for documents that certify a person immune and several experts saying the claim would not just be specious but also lead to discrimination and 'intentional' cases.
With a vaccine several months, if not a year, away, the proposal for a document to certify that an individual has been infected and therefore immune to SARS-CoV-2, which causes the infection, is centre-stage of discussion as the world navigates its way out of the pandemic.
Looking for ways out of the restrictive physical distancing measures imposed to control the spread of the novel coronavirus, several governments, including Chile, Germany, Italy, the UK and the US, have suggested the use of 'immunity passports'.
Individuals in possession of an 'immunity passport' could be exempt from physical restrictions and may return to work, school and daily life.
"An 'immunity passport' is a certification that would mark an individual immune to SARS-CoV-2 infection," said virologist Upasana Ray.
The rationale behind certifying people immune is the production and presence of antibodies against the virus, Ray, a senior scientist at the Kolkata-based CSIR-Indian Institute of Chemical Biology (IICB), said.
India, however, has been more cautious in its approach. "There is no evidence yet that a person infected with COVID-19 cannot get the infection again. There are reports from South Korea of re-infections, so providing 'immunity passports' on the basis of SARS-COv-2 antibodies in the blood isn't feasible," said Manoh Murhekar, director of ICMR's National Institute of Epidemiology in Chennai.
However, India allows travel for those who have the Aarogya Setu app installed on their phones -- showing a green band declaring the person safe. This is based purely on self-declaration.
As cases of the novel coronavirus cross 5.6 million with more than 3,50,000 fatalities, the WHO has said there is no evidence to suggest that people who have recovered from COVID-19 and have antibodies are protected from a second infection.
In addition to the technical complexities, 'immunity passports' also pose regulatory and ethical concerns, said experts.
"This idea of 'immunity passports' can lead to great difficulty in administrative implementation, and is likely to be accompanied by widespread abuse in a variety of ways, especially for poor and underprivileged groups," said immunologist Satyajit Rath.
Writing in The Lancet, Alexandra L Phelan from Georgetown University Medical Center in the US noted that 'immunity passports' would impose an artificial restriction on who can and can't participate in social, civic, and economic activities. This might also create a perverse incentive for individuals to seek out infection.
This will especially apply to people who are unable to afford a period of workforce exclusion, compounding existing gender, race, ethnicity, and nationality inequalities, he said.
"Such behaviour would pose a health risk not only to these individuals but also to the people they come into contact with," he wrote.
In countries without universal access to healthcare, those most incentivised to seek out infection might also be those unable or understandably hesitant to seek medical care due to cost and discriminatory access, Phelan noted.
Adding to the discussion, IICB's Ray asked what would happen to those negative for anti-SARS-CoV-2 antibodies. There is no evidence that herd immunity will develop, she said, adding that the duration it would last is unknown even if it somehow does.
Herd immunity is a form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection, whether through vaccination or previous infections.
"Shall we wait for these people to get infected and attain immunity to be able to get certified? This might also lead to discrimination," she added.
There is no evidence that all individuals would produce good quality antibodies, or that the neutralising antibodies that would protect them from re-infections. She added antibodies just like other proteins may not persist in the body for long.
The IICB scientist said SARS-CoV-2 has many variants which differ at the genetic level. Another problem with 'immunity passports', Ray noted, is that mere production of antibodies does not imply they can neutralise or stop the virus from gaining entry in the host.
Rath, from the National Institute of Immunology (NII) in New Delhi, agreed with Ray, saying that while the technical idea of 'immunity passports' is feasible in principle, there are many reasons why it is currently difficult in practice.
"A major part of the problem is to do with the technical issues involved with measuring the relevant 'immunity'," said Rath.
He said there are no validated tests to identify the actual levels of detectable immunity in the form of antibody amounts or the exact kinds of immunity showing strong enough correlations with real protection against infection to be usable as 'immunity passport' thresholds.
Finding and validating these thresholds is likely to take time-consuming research, in part because these levels seem to be quite variable, Rath explained.
"Such work is ongoing, but I have not yet seen any substantive results. Further, how long these threshold levels are maintained over time will quite possibly differ from person to person, and therefore, there will be yet another problem for these 'immunity passports' in terms of the length of their validity before they will need re-testing and 'renewal'," he said.
Another Indian virologist, who did not want to be named, highlighted that not much is known about the false positivity in antibody test. It may depend on the geographical area and the prevalence of other existing diseases, he added.
"This means a person carrying 'immunity passport' may not have protective immunity. So it may not be a good practice to issue 'immunity passports' based on some rapid tests," the virologist noted.
Considering the possibility of the novel coronavirus evolving even within a country, Ray said, re-infection with a different variant will not be surprising.
"Travelling to a different country or continent would also increase the probability of getting challenged by a different virus type against which the person might not be able to produce neutralising antibodies," she said.
Today's asymptomatic might become symptomatic under challenge with a different virus variant later, or if such people travel to a country where some other variant is dominating, she said.
The scientists noted that Instead of depending solely on naturally obtained immunity, it is better to invest time, effort and money to develop carefully designed vaccine candidates that show cross neutralising properties, and are applicable universally.