You must only make a report under RIDDOR (The Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013) when:
Dangerous Occurrences
If something happens at work which results in (or could result in) the release or escape of Coronavirus you must report this as a dangerous occurrence. An example of a dangerous occurrence would be a lab worker accidentally smashing a glass vial containing Coronavirus, leading to people being exposed.
Cases of Disease: Exposure to a Biological Agent
If there is reasonable evidence that someone diagnosed with COVID-19 was likely exposed because of their work you must report this as an exposure to a biological agent using the case of disease report. An example of a work-related exposure to Coronavirus would be a health care professional who is diagnosed with COVID-19 after treating patients with COVID-19.
Work Related Fatalities
If someone dies as a result of a work-related exposure to Coronavirus and this is confirmed as the likely cause of death by a registered medical practitioner, then you must report this as a death due to exposure to a biological agent using the ‘case of disease’ report form. You must report workplace fatalities to HSE by the quickest practicable means without delay and send a report of that fatality within 10 days of the incident.