COVID-19 Mortality Working Group: Lower excess mortality in September and October 2022

Catch up on the Actuaries Institute’s COVID-19 Mortality Working Group’s latest analysis of excess deaths.

In summary:

Total excess mortality for the months of September and October is estimated at 5% (+700 deaths) and 3% (+500 deaths) respectively, relative to expected mortality at pre-pandemic levels. These are the lowest excesses we have seen in 2022 and are a combination of fewer COVID-19 deaths and lower-than-expected respiratory deaths following the earlier-than-normal end to the flu season.
Total excess mortality for the first ten months of 2022 is 11% (+16,600 deaths).
Just over half of the excess mortality for the first ten months of 2022 is due to deaths from COVID-19 (8,900 deaths), with another 2,500 due to deaths with COVID-19.
The remaining 5,200 excess deaths have no mention of COVID-19 on the death certificate.

Background

The COVID-19 Mortality Working Group has examined in some detail the Provisional Mortality Statistics released by the Australian Bureau of Statistics (ABS) each month. For the month of January 2023, the ABS released only a short-form summary of the usual release, covering deaths occurring prior to 31 October 2022 and registered by 31 December 2022. No information was provided by cause of death, other than showing COVID-19 deaths separately. Therefore, we have been unable to analyse the data in our usual manner, and this article covers the main highlights only. (The ABS will return to their normal reporting next month.)

In this article, we separate COVID-19 deaths into:

Deaths “from COVID-19”, namely deaths where COVID-19 is listed as the primary/underlying cause of death; and;
Deaths “with COVID-19”, namely deaths where the underlying cause of death has been determined as something other than COVID-19, but the virus was a contributing factor.

This terminology is consistent with that used by the ABS and reflects the data provided.

In this article, we calculate excess deaths by comparing observed deaths to our “baseline” predicted number of deaths for all-cause mortality. Further details on our approach and methodology can be found in previous articles.

Excess deaths to 31 October 2022

The latest ABS release shows 159,965 deaths occurring in the ten months to 31 October 2022 that were registered by 31 December 2021. This compares to 144,650 deaths occurring in the nine months to 30 September 2022 that were registered by 30 November 2021. That is, an additional 15,315 deaths were registered in the month of December 2022. These registrations will mainly be for deaths that occurred in October 2022, but some will be late registrations in respect of earlier months.

Some October 2022 deaths will not have been registered by 31 December. However, we consider that the late registrations in December would broadly offset this shortfall. That is, we have assumed that the 15,315 deaths registered in December are a reasonable proxy for the number of deaths that occurred in the month of October 2022.

Our baseline predicted number of deaths for October 2022 is 14,800, thus resulting in estimated excess deaths of around 500, or 3%.

The latest ABS release shows that 235 deaths from COVID-19 and 96 deaths with COVID-19 in the month of October were reported by 31 December. Allowing for a small number of late registered deaths, we have assumed there were 250 deaths from COVID-19 and 100 deaths with COVID-19 in the month of October. This contributes about 2% and 1% respectively to the excess mortality for this month.

Table 1 shows our estimate of excess deaths for each month of 2022, while Figure 1 shows the same information graphically. Note that, as discussed above, these estimates are based on less data than usual. Our figures for October involve more approximation than usual.

The months of September 2022 and October 2022 have the lowest levels of excess deaths seen in 2022. We can see two clear drivers for this result. Further analysis will be undertaken when more complete data is available.

The number of deaths from and with COVID-19 each month is considerably lower than in previous months, with October falling below the previous monthly low (March 2022).
The influenza season was earlier than usual in Australia. Our baseline for August to October includes a “pre-pandemic” level of influenza and other respiratory deaths, but the flu season in Australia in 2022 occurred in June and July. This means that there is significant negative excess mortality in respect of respiratory disease in these later months. Note, however, that the non-COVID-19 excess is not negative; in August and September, excess deaths from ischaemic heart disease, cerebrovascular disease, diabetes, and “other” causes more than offset the negative respiratory excess. We expect that this will also be the case for the month of October 2022.

Disclaimer: We are not medical professionals, public health specialists or epidemiologists. This note is based on publicly available information and our general observations on that data.