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Information Note - Assignment of COVID-19 as Underlying Cause Of Death (UCOD)

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The Yearly Summary 2021 provides data on births, deaths and marriages registered in all four quarters of 2021 and, in the case of deaths, there are a number of points to consider:

  • It is important to note there will be a number of deaths where COVID-19 will not be assigned as the Underlying Cause of Death (UCOD) and therefore, the COVID-19 deaths in this release will vary from those put into the public domain by the Department of Health. Mortality statistics included in this release are classified by the UCOD assigned. COVID-19 deaths classified as a multiple cause of death but not as the UCOD are presented in Table 17 of the yearly summary 2021 release.
  • The Central Statistics Office (CSO) adhere to the World Health Organisation (WHO) ICD-10 International Classification of diseases 10th revision classification and selection rules and therefore the Mortality Coders in the CSO assign an Underlying Cause of Death (UCOD) to each death record using these WHO selection rules. COVID-19 is classified by the WHO when:
  1.           confirmed by laboratory testing irrespective of severity of clinical signs or symptoms.
  2.           diagnosed clinically or epidemiologically but laboratory testing is inconclusive or not available.
  • In accordance with these WHO rules, the selection of COVID-19 as the UCOD is dependent on where COVID-19 is placed in the hierarchy of a death certificate by the certifier. WHO selection rules are applied to the causal sequence and the UCOD is selected and tabulated by the CSO. Certifiers should report the underlying or originating cause on the lowest used line on the death certificate and a sequence of events leads from the underlying cause up to the immediate (direct) cause in the first line, 1(a). Not all conditions present at the time of death have to be reported—only those conditions that actually contributed to death.
  • Persons with COVID-19 may die of other diseases or accidents, such cases are not deaths due to COVID-19 and the WHO has recommended they should not be certified as such. For example, when classifying COVID-19 there should be no period of complete recovery between the illness and death. Persons with COVID-19 may die due to other conditions such as myocardial infarction but COVID-19 would not be a significant condition contributing to death if reported in Part 2 of the death certificate. Again, such cases are coded using WHO selection rules and are not deaths due to COVID-19.
  • A COVID-19 death is defined, for surveillance purposes, as a death resulting from a clinically compatible illness in a probable or confirmed COVID-19 case, unless there is a clear alternative cause of death that cannot be related to COVID-19 (e.g. trauma).

In addition, it should be noted that the CSO disseminates quarterly data on births, deaths and marriages, within five months of the end of the relevant quarter. This dissemination is dependent upon the life event being registered with the General Registration Office (GRO) and subsequently transmitted to the CSO.  Therefore, the life event must be registered before it is included in the quarterly releases and mortality data based on date of registration is regarded as provisional.  Final data, based on the date the death occurred, will be disseminated 22 months from the end of 2021, i.e. October 2023. There may also be additional delays in the registration of these events due to the COVID-19 pandemic.

The General Register Office and the HSE are continuing to work on changes to the death registration process to ensure that deaths are notified in a timelier fashion and submissions made as part of a public consultation on these proposals are currently being reviewed.

Finally, as a result of the COVID-19 pandemic, the CSO began to explore experimental ways of obtaining up-to-date mortality data. The CSO has therefore published a number of releases based on an analysis of death notices using the website

The initial analysis explored the use of death notices on to measure trends in mortality, finding a strong correlation between death notices and official CSO mortality statistics. In November 2020, subsequent analysis continued on this work, expanding the excess mortality analysis as well as updating the data to include 12 months’ worth of death notices and the newest release was issued at the end of April 2021. Link to: release. These releases include an analysis of recent mortality trends and also include an estimate of excess mortality over the period of the COVID-19 pandemic.   


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