20th Australian Population Association Conference: Opening Address

A tale of two pandemics in Australia: 1918-19 Influenza and COVID-19

Dr David Gruen AO
Australian Statistician
Wednesday 23 November 2022

Introduction

It is my pleasure to be invited to give the opening address at the Australian Population Association’s 2022 Conference.

While I am not a demographer, I have a keen interest in population and demography and today I want to talk about Australia's experience with two pandemics: the 1918-19 Influenza and COVID-19.

Influenza deaths in the 1918-19 panademic

  • Comparing number of flu deaths in years preceding the flu pandemic – a way getting at the concept of excess deaths (i.e. compared to an expected average).
  • Expected average based on 1911-1917 deaths – very low expected deaths.
  • Once the Influenza pandemic arrived, excess deaths were almost immediate and in large numbers – most of deaths occurred in a condensed period of time – within the first 10 months of the flu strain arriving in Australia.
  • Population of Australia at this time 5.3 million.
  • Total Australian deaths from this flu pandemic – at least 12,000.

Weekly all cause deaths 2019-2022

  1. Dates for key events are indicative only and may differ to other sources. 
  2. Data is provisional and will change as additional death registrations are received.
  3. 2016 is the starting point for the regression when modelling the projected number of deaths. 
  4. Data includes all doctor certified deaths occurring by the end of February 2022 and registered and received by the ABS until 30 April 2022. 
  5. People who died with COVID-19 as an associated cause of death (as opposed to the underlying cause of death) are included in the without COVID-19 series.
  6. Data is for January and February is expected to be approximately 98% complete. See section on Timeliness and completeness of data for more information.

Source: Measuring Australia's excess mortality during the COVID-19 pandemic (doctor-certified deaths)

  • Focus on episodes when number of deaths falls outside the confidence interval.
  • Vastly different to the ‘excess’ deaths pattern for the influenza epidemic of 1918-19 – with COVID, deaths have occurred over longer period with number of deaths picking up almost two years into the pandemic – as opposed to 1918-19 when large numbers of flu deaths occurred three months into the pandemic.
  • Higher numbers of deaths in 2022 reflect policy shift towards living with the pandemic, post mass vaccination of the population
  • Contrast with 1918-19 – when there was no effective vaccination developed. There was even an unresolved debate about whether the pandemic was viral or bacterial in origin.
  • During first wave lockdowns in mid 2020, deaths dropped below the expected rate. Fewer accidents, deaths from flu etc. as a result of lockdowns suppressing transmission, as well as changed behaviour of population.
  • Based on new data the ABS releases to support understanding of COVID-19. First released in June 2020, it provides weekly data.

Weekly all cause deaths, August 2021 - July 2022

  1. Data is by occurrence.
  2. Data is provisional and subject to change.
  3. Weeks are defined as seven-day periods which start on a Monday as per the ISO week date system. Refer to 'Weekly comparisons' on the methodology page of this publication for more information regarding the data in this graph.
  4. The baseline includes deaths from 2015-19 (for 2021) and from 2017-19 and 2021 (for 2022).
  5. Change in baseline was introduced

Source: Provisional Mortality Statistics, Jan - Jul 2022

  • Here are the more recent outcomes – this chart shows an extra five months of data, to July 2022.
  • 16,375 estimated excess deaths Jan to July 2022. However, this is a crude estimate with no adjustments for population growth or improvements in disease treatment. We’d expect the number of excess deaths for Jan to July 2022 to be approximately 14,000-14,500 when taking the aforementioned into account. 
  • To be compared with estimated flu deaths in 1918-19 of at least 12,000.
  • Australian population at time of 18-19 flu pandemic was about 5.3 million. Now nearly 5 times larger at close to 26 million.

Age-standardised all cause death rates

Source: ABS Deaths collection and ABS Provisional Mortality collection

  • A broader look at all causes of mortality over past century or so shows the different level of impact of the two pandemics.
  • The spikes at the time of the 1919 Influenza epidemic are noticeable.
  • In comparison – a small up-tick in 2021.
  • Likely to be a larger uptick in 2022, but that is strongly influenced by age distribution of COVID-19 deaths.
  • Age standardisation is based on 2001 Australian population distribution.

Age distribution of COVID-19 deaths

  • Wave 1: March to May 2020; Wave 2: June to November 2020; Delta Wave: July to December 2021; Omicron Wave: Jan to Sept 2022.
  • In all four waves, people aged 80-89 years had both the largest number and proportion of deaths due to COVID-19.  
  • In second wave, almost 80% of deaths were of people aged 80 and over.
  • The Delta wave was the only wave where more than half of the deaths (53%) occurred in people younger than 80 years old. During the Omicron wave, 71% of deaths were of people aged 80 or older. This proportion has varied considerably during the wave, ranging from 60% in March to 77% in June.
  • Age distribution of total closely resembles age distribution during the Omicron wave – because a big majority of COVID-19 deaths occurred during the Omicron wave.
  • As Assistant Minister Leigh will discuss in more detail at tomorrow night’s Borrie Lecture, death rates not even across the population.
  • Deaths rates for Australian born were 27.8 per 100,000 but much higher for some other groups. Examples:  for those born in Tonga (178.9), Samoa (178.2), Syria (118.3), Romania (97.1) and Iraq (91.0).
  • Across all waves, deaths were higher among the more the disadvantaged: overall, there were three times as many deaths in the lowest income quintile than in the highest income quintile.

Age-specific death rates

Source: AIHW Grim Books and ABS Provisional Mortality Statistics collection

  • For COVID-19, death rates are only high enough to be visible on the chart from age of 50 onwards, with rates for those 85+ being hugely higher than for younger age groups.
  • Data is to September 2022.
  • Rates of COVID deaths as a proportion of the whole age cohort in each case, not proportions of those who caught the flu or COVID.
  • Strikingly different age distribution for the two pandemics.
  • Death rates much higher during the Influenza pandemic overall and across all ages other than the very oldest age groups.
  • In the 1918-19 pandemic, 80% of flu deaths were people aged under 50, a stark contrast with COVID-19, for which less than 2% of COVID deaths were aged under 50 years. Spread of disease - males at high risk- hypotheses- generally in the working population and social constructs led to males being in other places such as sporting events, hotels, workplaces etc.
  • With COVID-19, most deaths were older, generally people aged 80+: Spread of disease - Vulnerable populations - aged care residents, those with pre-existing conditions and disability.
  • Similar sex ratio of deaths in the two pandemics: 1919 = 1.4 males for every female, COVID-19 = 1.3 males for every female.

Proportion of deaths from and with COVID-19 during the Omicron wave

During the Omicron wave: 

  • The proportion of people dying with rather than of COVID-19 of all COVID-related deaths has increased over the course of 2022. Vaccination has played a part in this as those vaccinated are less like to develop COVID pneumonia.  So death now more likely for those who are old/ vulnerable who get COVID, e.g. most common cause of death for those who die with COVID is cancer.
  • From March 2022, over 20% of COVID-19 associated mortality are deaths where the person has died with COVID-19. 
  • Close to 30% of COVID-19 associated deaths in August were of people dying with COVID-19. 

Life expectancy: International comparison of top 10 countries, United Nations

  • Australia was one of the few countries that showed increases in life expectancy in the first two years of the COVID-19 pandemic and has the third highest life expectancy in the world according to the United Nations’ estimates.
  • Other countries that did not see declines in life expectancy in 2020 were Norway, Denmark, Finland (for females only), New Zealand and Korea.
  • Higher death rates due to COVID 19 in 2022 may lower Australia’s life expectancy in 2022.
  • Apart from 2020, the graph shows the top 10 countries. For life expectancy.
  • In 2021, Australia’s life expectancy at birth increased slightly – by 0.1 years for both males and females (rates based on 2019-2021 average).

Crude birth rate

Source: ABS, Historical Populations

  • Fertility – some higher numbers of births in 2021 for Australia (some protective factors with pandemic).
  • The fertility rate in Australia was low in 1919 during the influenza outbreak, likely affected by the number of pregnant women who died (some evidence pregnant women had high death rates from flu) and some reports of higher numbers of stillbirths for the year for those infected with flu.
  • In 2021 crude birth rate was 12.1 per, 1,000 women (up from 11.5 in 2020).
  • Total fertility rate was 1.7 babies per woman.

Net overseas migration

  1. Estimates from 1972 are year ending June, prior to this they are year ending December. Estimates for 2020-21 are preliminary. See revision status on the methodology page.
  • We now move to the next component of population.
  • Lots of events have shaped overseas migration.
  • Again, the two pandemics have shown a completely different pattern.
  • Recently, we have seen what we call the “COVID-19 cliff”, whereas the opposite happened during the influenza of 1919. The flu pandemic hit at the end of WW I – after a prolonged period of low migration and coinciding with a massive migration influx at the end of the war – this was not stopped by the flu pandemic. Instead, quarantine was used to stop spread of disease in community.
  • In contrast, COVID-19 hit at a time of prolonged high level of overseas migration which plummeted when stringent international border restriction were introduced. 2021 saw negative net overseas migration for the first time since 1947.

Components of population change by capital city

Components of population change by capital city 2018-19

Components of population change by capital city

Components of population change by capital city 2018-19

The chart displays the components of population change for each Australian capital city in 2018-19 compared to 2020-21. Data for this chart is located below under the 'Data for the components of population change by capital city' heading.

  • I will now touch on internal migration. Can’t do a comparison with 1919 as we only introduced component based regional population since 2016.
  • Popular reporting is that there is a mass exodus from capital cities to the regions.
  • This is partly true but not the whole story. In 2020-21 during the height of the COVID-19 lockdowns, the smaller capitals grew while larger ones (Sydney and Melbourne) contracted. 
  • Lockdowns and cross border restrictions did play a role in the pattern of movements.
  • Now that Australia had moved into the next phase of “living with COVID” it will be interesting to see how the internal migration patterns will play out.

Additional information

  • People living in the capitals increased by 2.5 million (17%) between 2011 and 2021.
  • Regional Australia grew by 832,000 (11%) over this time.

Data for the components of population change by capital city

Components of population change by capital city 2018-19
 Natural IncreaseInternal MigrationOverseas MigrationPopulation change
Sydney38,701-25,55573,91987,065
Melbourne33,8592,25277,369113,480
Brisbane17,88415,91418,78952,587
Adelaide4,914-3,91412,90013,900
Perth14,837-1,40213,97027,405
Hobart7339861,7263,445
Darwin1,530-3,213542-1,141
Canberra3,409-1943,1106,325
Components of population change by capital city 2020-21
 Natural IncreaseInternal MigrationOverseas MigrationPopulation change
Sydney36,943-34,849-7,245-5,151
Melbourne27,363-33,501-54,367-60,505
Brisbane17,39715,001-10,52821,870
Adelaide5,252-226-3,1311,895
Perth15,0836,468-5,38216,169
Hobart863-828-369-334
Darwin1,656-1,602-381-327
Canberra3,318357-3,277398

Components of population change by rest of state

Components of population change by rest of state

Components of population change by rest of state

Components of population change by rest of state

The chart displays the components of population change by rest of state in 2018-19 compared to 2020-21. Data for this chart is located below under the 'Data for the components of population change by rest of state' heading.

This is the corollary of the previous graph – we see the heightened importance of internal migration (red section of the stacked bar) to the regions in the three largest states

Data for the components of population change by rest of state

Components of population change by rest of state 2018-19
 Natural IncreaseInternal MigrationOverseas MigrationPopulation change
NSW6,5783,49212,14022,210
Vic.3,2859,9467,22020,451
Qld11,9456,91713,38932,251
SA343-441,2411,540
WA3,209-5,0491,93191
Tas.3871,0221,3352,744
NT997-1,15822766
Components of population change by rest of state 2020-21
 Natural IncreaseInternal MigrationOverseas MigrationPopulation change
NSW7,44618,0271,30526,778
Vic.2,32615,154-1,76715,713
Qld11,95516,178-4,01524,118
SA2881,121-1851,224
WA3,387-1,117-3941,876
Tas.475719-811,113
NT989-902-861

Conclusion: Data insights and opportunities

Richness of ABS data to support analysis of impact of the COVID-19 pandemic on the population

  • introduced more timely, frequent and relevant data to support analysis and response.
  • adjusted methods to respond to changing environment (including running a Census during a pandemic).
  • harnessed new powerful integrated data assets to improve quality and provide new insights.
  • continue on this path of continuous improvement, building on what we’ve learnt and expanding data opportunities.

This presentation has dipped into the range of population data we have which can inform on the impact of the pandemic. The ABS introduced a range of new measures during the pandemic – not just on population, e.g. Weekly payroll jobs and wages, rapid surveys of households and businesses.

For population statistics, examples include up to date and rich analysis though provisional deaths, early indicators through provisional overseas arrival and departures data, more frequent Net Overseas Migration revisions and adjustments to preliminary model to account for changed traveller behaviour, more accessible information on international students, treatments to handle impact of vaccination programs on internal migration data (sourced from Medicare).

Also harnessed integrated assets to support policy response to vaccination with timely regularly updated data – as you’ll hear on Friday from Dr Phillip Gould in his plenary. Also used integrated data to support Census and assure its quality, and to support population rebasing. There are huge gains to be made through the use of administrative data, and these continue to be realised, often as a by-product of the increasing aspects of our lives now being intermediated through digital platforms.

Thank you.

Back to top of the page