New COVID-19 cases definition to include multiple infection episodes from 31 January 2022

From 31 January 2022, the Department of Health will move all COVID-19 case reporting to use a new episode-based definition which includes possible reinfections.

Reinfections have previously been included in daily updates of new COVID-19 cases, but re-infections were only counted once in cumulative totals.

On the dashboard, the change means:

• cases by report date will change to the new definition of an episode of infection
• historical numbers by report date will not be revised, so there will be a step increase in the cumulative numbers of cases on that date
• specimen date metrics will be revised back to the beginning of the pandemic, in the dashboard graphs showing trends
• the same metric names will still be used
• new metrics will show first episodes of infection and episodes of reinfection, shown by specimen date only

The Department is working with the UKHSA and other devolved administrations to align definitions across the UK.

Additional details

As the pandemic continues and more variants emerge, it is more likely that people will be reinfected with COVID-19. Contact tracing and health protection work at PHA follows up people with a positive test result, whether they were a new case or a case of reinfection. However, surveillance figures only report COVID-19 cases as the date of the most recent infection, so individuals are only counted once.

UK public health agencies are now updating surveillance data to count infection episodes, including reinfection episodes. Infection episodes will be counted separately if there are at least 90 days between positive test results. Each episode begins with the earliest positive specimen date. If someone has another positive specimen within 90 days of the last one, this is included in the same episode. If they have another positive specimen more than 90 days after the last one, this is counted in a separate episode (a possible reinfection episode).

Notes to editors: 

1. Additional information is available from:
   Information Analysis Directorate
   Department of Health
   Annex 2, Castle Buildings
   Stormont
   Belfast BT4 3SQ
   Telephone: 028 9052 2340
   E-mail: statistics@health-ni.gov.uk
2. For media enquiries please contact the DoH Press Office by email pressoffice@health-ni.gov.uk.
3. Follow us on Twitter @healthdpt
4. The Executive Information Service operates an out of hours service for media enquiries only between 1800hrs and 0800hrs Monday to Friday and at weekends and public holidays. The duty press officer can be contacted on 028 9037 8110.

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