Since week 38 of 2020, the number of tests reported are corrected for underreporting from virological laboratories. The estimated number of tests is obtained by multiplying the weekly total number of tests reported from virological laboratories by the weekly ratio of COVID-19 notifications by municipal health services to positive tests reported from virological laboratories. From week 12 of 2021 up until week 12 of 2022, the number of entry tests for events and activities, as reported by ‘Stichting Open Nederland’, were being collected and were added to this data. From week 29 up to and including week 39 of 2021, the number of tests for commercial testing of outbound travellers, sourced from the various commercial testing organizations as reported by ‘the Ministry of Infrastructure and Water Management’, were added to these data. From March 31st 2021 until April 11th 2022, a positive self-test result needed to be confirmed at the Public Health Services’ system (PHS, in Dutch: GGD). From April 11th 2022 this is no longer required.
From January 1st 2023, the RIVM is collecting less additional information from people that have tested positive for SARS-CoV-2. As a result, we will not report any deaths anymore from January 1st 2023 and onwards, which will not affect the total number of cases reported in the NCOVAGGR file. Moreover, there is an underreporting in the number of deaths in data up and till 31st December 2022. This is due to the fact that it has never been obligatory to report deaths due to COVID-19 in the Netherlands. Because of this, PHS and RIVM do not have a complete overview of all deaths related to COVID-19. This underreporting did not affect the total number of cases reported in the NCOVAGGR file. In addition, in the reported data it was not possible to differentiate between persons who died with a COVID-19 infection and those where COVID-19 was the main cause of death. Statistics Netherlands is monitoring deaths attributed to COVID-19.