As the news of potential new vaccines and tests for Covid-19 developed by labs around the world seems to make the news each day, the optimists among us have started to look for signs that we might be moving towards the easing of lockdown restrictions in Europe and the US, following from the relaxing of measures in New Zealand and Australia. The phrase on everyone’s lips is “exit strategy”.

In the UK, the lack of communication from the government about their “exit strategy” has prompted criticism from the shadow cabinet, although scientists have warned that with no “good options”, publicising an exit strategy could be risky.

Much of the debate about how we might begin to lift restrictions has centred around the need for an antibody test. If we were able to tell who had been infected and had recovered, and if those people could demonstrate immunity against catching the virus again, could we begin to allow them to go back to work?

This is dependent on a number of things, including developing a proven antibody test. Antibodies are proteins produced by the immune system to target a virus, bacterium or other pathogen. They destroy the pathogen by binding to it and making it harmless, or by flagging it for destruction by immune cells. Antibodies typically linger on in the bloodstream after an infection, in case the virus returns. If it does, the antibodies are ready and waiting, which means immune response much faster – so much so that it might barely register as a second infection. What this means is that convalescent patients – those who have recovered – have resistance to reinfection.

Unfortunately, it might not be as simple as that, the World Health Organization (WHO)’s Maria van Kerkhove warned over the weekend – and the reason has much to do with the fact that this is a virus that had never been in a human host until the end of last year.