Context

The coronavirus pandemic has now shut down the activities and economies in many countries that are experiencing increasing numbers of COVID-19 cases. Experts are thinking about strategies for opening up once things start slowing down. A few countries have started considering issuing “immunity passports”.

About

• The idea for the “immunity passport” or a “back to work” pass is this: If you’ve been infected with SARS-CoV-2, the virus that causes COVID-19, and recover, then you have immunity that will protect you from getting the disease again for some amount of time.
• However, it is not known for certain that whether people do have immunity once they’ve recovered and how long that immunity would last. 

How immunity is developed?

• The development of immunity to a pathogen through natural infection is a multi-step process that typically takes place over 1-2 weeks.
• Response: The body responds to a viral infection immediately with a non-specific innate response in which macrophages, neutrophils, and dendritic cells slow the progress of virus and may even prevent it from causing symptoms.
• Adaptive response: This non-specific response is followed by an adaptive response where the body makes antibodies that specifically bind to the virus. These antibodies are proteins called
• Recognition & elimination: The body also makes T-cells that recognize and eliminate other cells infected with the virus. This is called cellular immunity.
• This combined adaptive response may clear the virus from the body, and if the response is strong enough, may prevent progression to severe illness or re-infection by the same virus.
• This process is often measured by the presence of antibodies in blood.

What did the WHO say?

• As per the World Health Organization, governments should not issue so-called "immunity passports" or "risk-free certificates" as a way of easing lockdowns.
• There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.
• Such a move could actually increase virus transmission. People who assumed they were immune might stop taking precautions.
• Some governments have considered permitting people who have recovered to travel or return to work.
• Most studies carried out so far showed that people who had recovered from infection had antibodies in their blood - but some of these people had very low levels of antibodies.
• This suggested that another part of the body's immune response - T-cells, which eliminate infected cells - may also be "critical" for recovery.

How would this help us in the response to the coronavirus pandemic?

• If everything works, the antibody tests and the assumption that recovered people get enough immunity to not get COVID-19 again, then immunity passports would help us get out of stay-at-home orders and economic shutdown.
• In theory, people who have an immunity passport could safely return to work because they would not get sick again and start passing the virus around. As tests become available, then business and activity could slowly return to normal.