Covid-19 Antibody Tests: Game-changer or Source of More Questions?

It appears that the antibody tests of 2 companies for Covid-19 have now been approved (they have high accuracy and specificity) for use in the UK and there has been a lot of hype about them being potential 'game-changers' (https://www.theguardian.com/uk-news/2020/may/14/covid-19-antibody-test-unlikely-to-be-widely-aviable-any-time-soon). In theory, the antibody test can tell us who has been infected with the virus. This test has been perceived as a potential route to a 'passport' to operate freely in society, as someone who is neither likely to catch the infection nor to pass it on to other people. The fact that, although test kits could be available en masse, but are only currently scheduled for use with NHS or care home staff, appears to reflect unanswered questions about the pandemic. We are not yet sure whether a) People who have the antibody cannot pass on the virus and b) That the antibody protection lasts for a substantial period of time. Having said that, I do think the tests could be rolled out more extensively to determine the proportion of the population who have been infected at one time or another by the virus (without any granting 'passport' status).