Studies on Covid-19 Lethality

Last updated: October 20, 2020; First published: May 12, 2020
Share on: Twitter / Facebook; Main article: Facts about Covid-19

Overview

1) Antibody studies 2) Immunological studies 3) Median age of death 4) Hospitalizations 5) Nursing homes 6) Overall mortality 7) Development IFR: Infection fatality rate

1) Antibody seroprevalence studies

The covid-19 infection fatality rate (IFR) depends on demographics (age and risk structure), public policies (e.g. protection of nursing homes), and medical treatment quality.

Covid-19 IFRs are strongly age-dependent, with a steep increase above the age of 70. The median age of covid-related deaths in most Western countries is 80 to 86 years (see section 3 below). In most Western countries, about half of all deaths occurred in nursing homes (see section 5).

In terms of covid-19 IFRs, an important difference exists between places with and without a partial or total collapse of local health and elderly care, and between the early and late pandemic phase.

A. Places without a collapse of health and elderly care
Country Published Population IFR (%) Source
Global Oct. 14 51 locations
Below 70 years
0.27³
0.05³
Ioannidis
Japan Sept. 23 Tokyo <70y 0.01 Hibino
USA Sept. 2 Indiana 0.265 AIM
Brazil Sept. 1
Sept. 21
Maranhao
Manaus
0.17
0.28
da Silva
Buss
Iceland Sept. 1 General population
Below 70 years
0.30
0.10
NEJM
Switzerland July 14
August 7
Geneva hotspot
Zurich area
0.32¹
0.30¹
Perez
Aguzzi
India July 31 Delhi
Mumbai
0.07²
0.12²
India
Africa July 29
August 5
Kenya
Malawi
0.01
0.01
Uyoga
Grace
Austria June 25 Ischgl hotspot 0.26 von Laer
Sweden June 16 Stockholm NNH
Stockholm <70y
0.356
0.09
FOHM
Slovenia May 6 General population 0.16 GSI
Germany May 4 Heinsberg hotspot 0.364 Streeck
Iran May 1 Guilan province 0.12 Shakiba
USA7 April 30
April 24
April 21
Santa Clara County
Miami-Dade County
Los Angeles County
0.17
0.18
0.20
Bendavid
Miami
Sood
Denmark April 28 Blood donors (<70y) 0.08 Erikstrup

1) 0.64% and 0.60% including nursing homes; 2) 0.14% and 0.23% assuming 40% missing fatalities (more); 3) median values; 4) the unadjusted IFR is 0.28% (page 9); 5) general population (excl. nursing homes); 6) 0.58% including Stockholm nursing homes (about 40% of deaths, see page 23); 7) These US studies may underestimate the true IFR, as they were done early during a locally accelerating pandemic.

Note: The much-cited Meyerowitz-Katz meta-study claiming a global Covid-19 IFR of 0.68% is misleading because it mixes modelling studies and antibody studies, nursing homes and the general population, early and late phase IFRs, and commits several methodological mistakes.

B. Places with a partial or total collapse of health and elderly care

Overview: 1) Spain 2) Northern Italy 3) New York City 4) England 5) Belgium

Places with a partial or total collapse of local health and eldery care experienced significantly higher and very strongly age-dependent IFR values, especially during the early phase of the pandemic.

However, IgG antibody tests may underestimate the true prevalence of coronavirus infections and may thus overestimate the IFR by a factor of two to five (see section 2 below).

1) Spain
Country Published Population IFR (%) Source
Spain August 7 Covid confirmed
Excess deaths
Below 50 years
Below 40 years
0.82
1.07
<0.10
<0.03
Pollan

A Spanish seroprevalence study found an overall IFR between 0.82% (based on confirmed Covid-19 deaths) and 1.07% (based on excess all-cause deaths). The study didn’t include nursing homes, which accounted for about 50% of all deaths. The IFR was strongly age-dependent, with values below 0.03% until 40 and below 0.1% until 50 but reaching very high levels above 70 years.

The study found a country-wide IgG antibody seroprevalence of just 4.9% (about 12% in Madrid). However, less than 20% of symptomatic people (3+ symptoms or anosmia) had IgG antibodies. This may indicate that infections were up to five times more widespread than detected by IgG antibody tests (see section 2 below on this topic). If so, Spanish IFR values might drop below 0.5%.

Above 60 years, there was a significant difference in lethality between men and women. This might be due to e.g. genetic reasons, cardiovascular health, or certain habits like smoking.

Spain: IFRs by age group and gender in confirmed cases (Barriuso)
2) Northern Italy
Country Published Population IFR (%) Source
Northern Italy August 6 Above 70 years
Below 70 years
Below 50 years
80+, first phase
80+, second ph.
10.5
0.43
<0.01
30.40
8.10
Poletti

An Italian study considered contacts of confirmed Covid-19 cases in the Lombardy region, which includes hotspots like Bergamo and Cremona, to determine their fatality risk and their comorbidities. They found that the overall IFR was 62% lower in the second phase of the pandemic (after March 16) compared to the first, cataclysmic phase (up to March 15).

This was particularly evident in people above 80, where the IFR dropped from 30% in the early phase to 8% in the later phase (4% for women, 16% for men). Below 50 years, IFRs were near 0%; below 70 years, IFRs were 0.43% (both phases combined). More than 80% of deaths occurred in patients with cardiovascular diseases, which are known to be an important risk factor.

Of note, among Italian people with anosmia (temporary loss of the sense of smell or taste), a very typical Covid symptom, only about 25% were found to have IgG antibodies. This could indicate that coronavirus infections are more widespread, and IFRs lower, than assumed.

Northern Italy: IFRs in early and late pandemic phase (Poletti)
3) New York City
City Published Population IFR (%) Source
New York City June 29 Overall 0.70 Stadlbauer
New York City June 29 Confirmed
Probable
25 to 44 y.
<25 years
1.10
1.45
0.12
0.01
Yang

Until May 2020, New York City counted about 20,000 confirmed and probable Covid-19 deaths among its 8.4 million citizens and registered an antibody prevalence of about 20%. Studies estimating the infection fatality rate (IFR) for New York City found values between 0.7% and 1.1% based on confirmed deaths and up to 1.45% based on confirmed and probable deaths.

About 52% of Covid deaths in NYC occurred in the 75+ age group. This value is lower than in Europe, where about 90% of deaths were 70+. In all of New York State, about 6,300 patients were sent from hospitals into nursing homes, which ultimately registered between 6,600 and 13,000 deaths.

As in Italy and other hard-hit places, the IFR for age groups above 65 dropped by about 50% during the course of the pandemic, possibly due to better medical preparedness and treatment strategies.

Assuming that serological IgG antibody tests do not capture the full extent of coronavirus infections (e.g. due to mild cases without IgG antibodies), the overall IFR in New York City might drop to about 0.50% or below, and the actual spread of the coronavirus might be above 50%.

Covid deaths in NYC by age group (Source: NYC.gov)
4) United Kingdom
Country Published Population IFR (%) Study
England August 21 July 28 (MCT)
July 28 (ONS)
0.30
0.49
CEBM
England August 14 General population
Incl. care homes
45 to 64 years
Below 44 years
0.90
1.43
0.50
0.03
Ward

Until July 2020, England counted about 30,000 Covid deaths in the general population and about 20,000 Covid-related deaths in nursing homes (which had to receive patients). According to the Oxford Centre for Evidence-Based Medicine, the Covid IFR fell by 50% to 80% during the epidemic and reached a value between 0.3% and 0.5% by the end of July.

A study by Imperial College London estimated an IgG antibody seroprevalence of 6% overall and 13% in London by mid-July. However, according to Public Health England, London blood donors had an antibody seroprevalence of 17.5% already in May.

Of note, only about 50% of people with anosmia (temporary loss of the sense of smell or taste), a very typical Covid symptom, had IgG antibodies. Only 35% of people who were suspected to be Covid cases by a doctor, had IgG antibodies. And only 28% of people who self-reported “severe symptoms” had detectable IgG antibodies against SARS-CoV-2.

If some of these people were indeed Covid cases (without detectable antibodies at the time of testing), the overall IFR value in the general population may drop to about 0.50% or below. The overall mortality of 2020 is comparable to the strong flu season of 1999/2000 (see below).

England: Mortality 2020 compared to strong flu wave of 1999/2000 (InProportion)
5) Belgium
Country Published Population IFR (%) Study
Belgium June 20 General population
Incl. care homes
45 to 64 years
Below 44 years
0.43
1.25
0.21
0.02
Molenberghs

Belgium reported one of the highest Covid death rates in Europe, in part because it always included confirmed and probable Covid deaths. 66% of excess deaths in Belgium occurred in nursing homes. Of these, only about a third were confirmed by a PCR test. It is possible that some of the non-confirmed nursing home deaths were not due to Covid, but due to the extreme circumstances.

Due to the high proportion of nursing home deaths, IFRs differ markedly between the general population and the nursing home population. The IFR for the general population is estimated between 0.30% to 0.62%, while the IFR for the nursing home population is estimated between 28% and 45%.  For people aged 45 to 64, the IFR is 0.21, and for people aged 25 to 44, the IFR is 0.02%.

Even without age-adjustment, the number of excess deaths due to Covid in April 2020 is comparable to the number of excess deaths in January 1951 and February 1960 due to strong seasonal influenza.

Belgium reported an overall IgG antibody seroprevalence of about 6% by May 2020. If actual infections are more widespread (including mild cases without IgG), the IFR in the general population might drop below 0.30%. As in other countries, above 65 IFRs are higher for males than females.

Belgium: IFR by gender and age in (non) nursing home population (Molenberghs)

2) Immunological studies

Immunological research indicates that serological antibody studies, which measure antibodies in the blood (mostly IgG), may detect only about 20% to 80% of all coronavirus infections, depending on the sensitivity of the assay, the timing of the test, and the population tested.

This is because up to 80% of people develop only mild symptoms or no symptoms if infected, as they neutralize the coronavirus with their mucosal (IgA) or cellular (T-cells) immune system. These people may develop no measurable IgG antibodies or may show them only for a few weeks.

Most global Covid-19 hotspots peaked at about 20% IgG antibody prevalence (e.g. New York City, London, Stockholm, Madrid, Bergamo). Moreover, among people with anosmia (temporary loss of the sense of taste or smell) – a very typical Covid-19 symptom – only about 20% to 50% had detectable IgG antibodies, according to surveys in several countries (see below).

See also: Are we underestimating seroprevalence of SARS-CoV-2? (BMJ, 09/2020) and Coronavirus up to five times more common and less deadly than assumed (SZ, 06/2020).

Country Published Focus Factor Source
Switzerland May 23 IgA 5 Report / Study
China June 16 IgG 6 Study¹
Sweden June 29 T-cells 2 Study
Spain July 6 IgG 5 Study²
Germany July 16 IgG 2 Study
Italy August 3 IgG 4 Study²
Brazil August 12 IgG 5 Study²
UK August 14 IgG 2 Study²

1) Only 16% of likely infected HCW had IgG; 2) People with anosmia but without IgG antibodies.

3) Median age of Covid-19 deaths per country

Half of all deaths were below, half were above the median age.

Country Median age
Source
Australia 82 years DOH
Austria 80+ years EMS
Brazil ~70 years SDS
Canada 86 years HCSC
England 80+ years NHS
France 84 years SPF
Germany 82 years RKI
Italy 82 years ISS
Spain 82 years MDS
Sweden 84 years FOHM
Switzerland 84 years BAG
USA 78 years CDC
Example: Death rate by age group in Massachusetts (mass.gov)

4) Hospitalization rate

Initial estimates based on Chinese data assumed a very high 20% hospitalization rate, which led to the strategy of ‘flattening the curve’ to avoid overburdening hospitals. However, population-based antibody studies (see above) have since shown that actual hospitalization rates are close to 1%, which is within the range of hospitalization rates for influenza (1 to 2%).

The US CDC found that Covid-19 hospitalization rates for people aged 65 and over are “within ranges of influenza hospitalization rates”, with rates slightly higher for people aged 18 to 64 and “much lower” (compared to influenza) for people under 18.

In local hotspots like New York City, the overall hospitalization rate based on antibody studies is about 2.5% (19.9% or 1.7 million people with antibodies and 43,000 hospitalizations by May 2).

The much lower than expected hospitalization rate may explain why most Covid-19 ‘field hospitals’ even in hard-hit countries like the US, the UK and China remained largely empty.

5) Percentage of Covid-19 deaths in care homes

In many countries, deaths in care homes account for 30 to 60% of all additional deaths. In Canada and some US states, care homes account for up to 80% of all “Covid19-related” deaths. In Sweden, deaths in nursing homes plus nursing apartments account for 75% of all deaths.

Care home deaths: absolute numbers (bars, left scale) and percentages (dots, right scale)

Source: Mortality associated with COVID-19 outbreaks in care homes (LTC Covid, May 21, 2020)

Source: The Covid-19 Nursing Home Crisis by The Numbers (Freopp, June 19, 2020)

The following chart shows the very significant difference between IFRs for the entire population (including nursing homes, top row) and for the non-nursing home population (bottom row) at the example of Belgium. IFRs for nursing home patients (ca. 30%) are about 10 times higher than IFRs for people of the same age (75+) outside of nursing homes (ca. 3%).

When calculating and communicating IFRs, it is therefore important to distinguish between nursing homes (which require focused and humane protection) and the general population.

Belgium: IFRs for entire population vs. non-nursing home population (Molenberghs)

6) Overall mortality

In countries like the UK (lockdown) and Sweden (no lockdown), overall mortality since the beginning of the year is in the range of a strong influenza season; in the US, mortality is in the range of the 1957 and 1968 influenza pandemics; in countries like Germany, Austria and Switzerland, overall mortality is in the range of a mild influenza season (but antibody levels are still low).

Sources: USA-1, USA-2, UK-1, UK-2, Sweden, Switzerland, Germany, Belarus

A comparison between the number of coronavirus deaths predicted by the influential model of Imperial College London (no measures or moderate measures) and the actual number of deaths in Sweden shows that the model strongly overestimated the impact of the epidemic:

Sweden: ICL model predictions versus actual Covid-19 deaths (HTY/FOHM)

7) Development of the pandemic

In countries without a lockdown (e.g. Sweden), the epidemic usually reached its peak within four to eight weeks of the outbreak. However, some reports showed cumulative deaths per day of report (left) instead of daily deaths per day of death (right), implying an ever escalating situation.

Cumulative deaths per day of report vs. daily deaths per day of death. (OWD/FOHM; April 24)
Cumulative deaths per day of report vs. daily deaths per day of death. (OWD/FOHM; April 24)

The United States is no exception to this dynamic. Rather, the US has seen several consecutive regional waves that each peaked within four to eight weeks of the regional outbreak.

US: Covid cases by region (C19C/CDC)

See also


Share on: Twitter / Facebook

WordPress.com.

Up ↑