many employers, the NHS has been hit by staff shortages as rising case numbers have led to high numbers of staff being “pinged” by the app and required to isolate for 10 days from first contact with someone who tested positive. Qualifying criteria will be determined on a case-by-case basis, it added, and “must be authorised by the organisation’s local Director of Infection Prevention and Control” or relevant director of public health. Staff that receive the exemption must self-isolate when not at work and if they do develop Covid symptoms should immediately stay at home. They will also not be permitted to work with clinically extremely vCritical staff in 'exceptional circumstances' – including some NHS workers, air traffic controllers and railway signallers – will be allowed to carry on working if they are exposed to someone that tests positive for Covid, the government has announced. From today (19 July), frontline staff where absences could lead to “a significant risk of harm” will be exempt from having to self-isolate if the NHS Covid-19 app advises them to.