Declining COVID-19 Case Fatality Rates across all ages: analysis of German data
September 9, 2020
Jason Oke, Daniel Howdon, Carl Heneghan,
This analysis shows that the fatality rate from COVID-19 has declined in all age groups, and the older age groups drive the overall reduction.
We have previously documented that the UK case-fatality rate (CFR) has fallen substantially from its peak in April. One explanation is that, unlike in March and April, new cases are predominantly in younger people who have a better outcome.
We, therefore, sought to examine trends in CFR over time to see if the fatality rate was declining across all age groups.
Due to the absence of age-stratified case data in the UK (although we’re working on this) we have used German data which reports lab-confirmed cases and deaths by broad age categories.
To illustrate changing CFR, we provide both simple descriptive statistics and a more sophisticated approach that we have used before, to account for the lag between cases and deaths.
Germany has experienced a lower CFR than other similar European countries, something which has been attributed to higher rates of testing and more confirmed cases.
The figure below shows the trend (log scale) in cases and deaths since week 10 (week commencing 3rd March) till week 35 (week ending 31st August). In the early phase of the pandemic, deaths in Germany mirrored cases, but the recent trend is for cases to increase whilst deaths continue to decline.
Crude estimates of the CFR over time show that for people aged 80 and over the average CFR was 29% up to week 18, fell to 17% in weeks 19 to 27, and for mid-July onwards the CFR was 11% – a decrease of 61%.
A larger decrease is seen in the ages 60-79 with average CFR ~ 9% in March/April falling to 2% in July August.
More granular estimates of CFR trends that take account of the lag between cases and deaths provide similar patterns with a steep decline from early April and levelling off in the summer months.
This analysis shows that the fatality rate from COVID-19 has declined in all age groups, and the older age groups drive the overall reduction.
Given German CFRs were low to start within the older age groups, it is likely in countries with higher CFRs at the outset, the effect could be more extensive.
Future work will focus on whether this pattern continues as we go into the Autumn and Winter and seek to address these issues in other countries, and further understand the reasons for these patterns.
Daniel Howdon is a Senior Research Fellow in Health Economics, Leeds Institute of Health Sciences. Bio here
Carl Heneghan is Professor of Evidence-Based Medicine, Director of the Centre for Evidence-Based Medicine and Director of Studies for the Evidence-Based Health Care Programme. (Full bio and disclosure statement here)
Jason Oke is a Senior Statistician at the Nuffield Department of Primary Care Health Sciences and Module Coordinator for Statistical Computing with R and Stata (EBHC Med Stats), and Introduction to Statistics for Health Care Research (EBHC), as part of the Evidence-Based Health Care Programme.
Disclaimer: the article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the authors and not necessarily those of the host institution, the NHS, the NIHR, or the Department of Health and Social Care.
