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What is the COVID-19 mortality rate based on cause of death?

Once a quarter Statistics Netherlands (CBS) compiles a mortality rate that is based on known cause of death (until July 2021 this was once a month). In this article we explain what this rate means, why it is not shown on the dashboard, and how it differs from the two other mortality rates shown on the dashboard.

This article explains the COVID-19 mortality rate that is based on cause-of-death certificates, and the difference between this rate and the mortality rates shown on the dashboard.

This article was originally published on 24 June 2021. It has been updated on 2 July 2021.

In order to know exactly how many people have died from COVID-19, CBS uses data provided by doctors. When someone dies, a medical examiner is required by law to fill out two forms: a death certificate and a cause-of-death certificate. The first form doesn’t state the cause of death, only that the person has died. The second form states the cause of death, for example that the person has died from COVID-19. Doctors send these forms to the municipality where the person died.

Mortality rate by cause of death

The municipalities send the cause-of-death certificates to CBS once a month. The law states that these forms must be completed on paper. This means CBS has to enter all the data from these forms manually and then encode them. This takes a few weeks. Only then can CBS specify the number of deaths for various causes of death, including COVID-19. We call this the mortality rate based on cause of death. CBS publishes this mortality rate every quarter (until July 2021 this was once a month). These figures reflect the situation approximately three months previously.

Completing a cause-of-death certificate

Photo credit: CBS / Alrik Swagerman

Mortality rate showing cause of death not on dashboard

We do not show the mortality rate based on cause of death on the dashboard because we only use data from the recent past, that is, data that we receive per day or week. This data is necessary to follow the epidemic closely and to be able to take timely measures. However, we think it is important to mention the mortality rate based on cause of death, because these are the most accurate figures.

What sort mortality data do we show on the dashboard?

The mortality rates that we show on the dashboard are:

The mortality rate based on reports to the GGDs
This is the number of deaths among patients with COVID-19 that are reported to the municipal health services (GGDs) each day. See article entitled What’s meant by number of reported deaths?

Graph showing the number of reported deaths from COVID-19 over time

The mortality rate based on excess mortality
This is the number of deaths that exceeds the projected number calculated by CBS. See the article entitled What’s meant by excess deaths?

Graph showing the total number of deaths per week

Why do these mortality rates differ?

The mortality figures on the dashboard differ from the CBS mortality rate based on cause of death.

The mortality rate based on reports received by the GGDs is lower than the mortality rate reported by CBS:

- The GGDs must be notified if someone tests positive for coronavirus. This requirement does not apply to deaths from COVID-19. There is only a notification requirement for living people who have tested positive. If the GGDs are not informed that a person who tested positive has died of COVID-19, this information will not be included in their mortality figures.

- If a person dies from COVID-19, but had not been tested for coronavirus by a GGD, then this person will not be included in the GGD’s mortality figures.

- NB: Very few tests were carried out during the first wave, but testing increased after that time. The figures from June 2020 onwards are a better reflection of the actual situation.

The CBS mortality figure based on excess mortality (mortality monitor) is lower than the CBS figure based on cause of death:

- The excess mortality rate reflects the number of people who have died in excess of what is expected. The mortality rates by cause of death make clear that the excess mortality from March 2020 to March 2021 was caused by COVID-19. Overall, the excess mortality rate is lower than the number of deaths from COVID-19 according to CBS cause of death. This is because some people who would have died anyway from other causes, such as cardiovascular or respiratory disease, have now died from COVID-19.

For example, if you compare the January 2021 figures, you can see the difference between the three mortality rates. The CBS cause of death figure – the most precise of the three death rates – is about twice as high as the other two figures.

Table showing mortality rates of January 2021

Note: In order to be able to compare the three figures in the table above, we added up the results of the first four weeks of this year for each figure. The deaths from 1 to 3 January are not included in the figures for ‘Reports to GGD’ and ‘CBS excess mortality’ because this data is delivered per calendar week.

You can also see the difference between the three figures when we add up the number of deaths from COVID-19 per month. Since CBS cause of death figures were only available up to the end of February on the day we published this article, the table below shows mortality rates up to the end of February (until the eighth week of 2021).

Table showing cumulative mortality rates up to the end of February 2021

If you look at the three summed mortality rates over time, you see the same thing. The mortality rate according to reports to GGD (the orange line) is the lowest, and the mortality rate according to CBS cause of death (the blue line) is the highest.

Different mortality rates (cumulative)

At the bottom of the mortality page on the dashboard is a link to the CBS website. From July 2021, CBS will publish a new report every quarter about the number of people who have died from COVID-19, based on the cause of death.