What have been the fatal risks of Covid, particularly to children and younger adults?

Summary

After nearly 45,000 Covid deaths in England and Wales, we can see that people of different ages have been exposed to dramatically differing risks. Fatalities among school-children have been remarkably low. Taking women aged 30–34 as an example, around 1 in 70,000 died from Covid over the 9 peak weeks of the epidemic. Since over 80% of these had pre-existing medical conditions, we estimate that a healthy women in this age-group had less than a 1 in 350,000 risk of dying from Covid, around 1/4 of the normal risk of an accidental death over this period.

Healthy children and young adults have been exposed to an extremely small risk during the peak of the epidemic, which would normally be deemed an acceptable part of life. Risks can be far higher for the elderly and those with pre-existing medical conditions.

Note added June 15th

This is an analysis of the risks faced by the general population over the peak of the epidemic. It does not tell us what the risks would have been had lockdown not occurred (presumably higher), or what the risks will be in the future (presumably lower).

As COVID-19 changes from being seen as a societal threat to a problem in risk management, it is essential that we get a handle on the magnitudes of the risk we have faced and may face in the future, and try to work out ways to communicate these appropriately. Fortunately new data and analyses permit more insight into the lethal risks that have been faced during the epidemic — note I am excluding potentially important non-lethal consequences of illness or treatment.

Note that everything from now on refers to the risks faced by people who were not currently infected.

Data from the Office for National Statistics covers deaths registered in England and Wales up to May 29th, and from these it is possible to calculate population fatality rates over the peak 9 weeks of the epidemic in broad age-bands.

Observed population fatality rates for deaths registered in England and Wales over the 9-week period 28th March to 29th May. ‘5-year average’ is the average number of deaths from all causes over this period, 2015–2019. ‘Covid deaths’ have Covid-19 mentioned on the death certificate, the overwhelming majority as a contributory cause of death.

The second row shows that 2 deaths have been recorded among over 7 million school children aged between 5 and 14 (around 1 in 3.5 million), an extremely low risk — although additional deaths may be reported following coroners’ investigations. Over the last five years, there has been an average of 94 deaths registered over this 9-week period for those aged 5–14, and so the 2 Covid deaths represents only 2% of the normal risk faced by this group. That is, whatever average risk they would have faced in these 9 weeks if Covid had never existed — a risk which was extraordinarily low — was increased by Covid by only 2%.

This reflects the finding that across 7 countries up to 19th May, there had been 44 Covid deaths recorded out of over 137 million 0–19 year-olds, a rate of less than 1 in 3 million, while this same group suffered over 1000 deaths from accidents over this same period.

At the other extreme, 1.8% (1 in 55) of the over-90s died with Covid-19 on their death certificates in these nine weeks. These 9,682 deaths can be compared to the average number over this period over the last five years, which is 18,523, so the ‘Covid risk’ represented an additional 52% of normal risk (this ignores the excess non-Covid deaths that have been recorded, due to either under-diagnosis of Covid or disruption to the health service). So for the over-90s, it’s as if Covid has exposed them to ‘an extra 33 days’ risk on top of the 9 weeks-worth they would normally have. This represents roughly 4,000 times additional lethal risk to which 15–24s have been exposed.

Taken as a whole, 1 in 1,318 of the population died and had Covid on their death certificate, which represents a 51% increase over the normal risk, equivalent to an extra 32 days over and above the 63 days which they would normally experience.

The table above only considers broad age groups, but more detailed population fatality rates are shown in the graphs below, for males and females in 5-year age-bands.

Covid population death rates for females and males on a logarithmic scale — data from ONS. ‘Normal risk’ is from ONS actuarial life tables, expressed as risk over a nine-week period.

The extraordinary linearity of the death rates on the logarithmic scale shows that Covid death rates have a fairly precise exponential increase with age, increasing at around 12–13% each year, corresponding to a doubling every 5–6 years. This means that a 20-year age-gap increased the risk by around 10-fold. So, compared to a 20-year-old, an 80-year-old had 10 * 10 * 10 ~ 1000 times the risk of dying.

The Covid population death rates are roughly proportional (ie parallel on a logarithmic scale) to ‘normal’ death rates for over 45s, but well below normal rates for younger ages. Note these are in addition to the normal rates.

The lesser relative effect of Covid on younger groups could be partly because their ‘normal’ risk will be more strongly influenced by accidents and non-natural causes, whereas Covid seems to multiply the risk of ‘natural causes’ — it just seems to take any frailty and multiply it.

A full table with detailed age categories is provided below.

Observed population fatality rates for deaths registered in England and Wales over the 9-week period 28th March to 29th May.

Let’s take a particular group of people, say the 2 million females between 30 and 34 in England and Wales. 29 deaths in this group have been registered with Covid, a rate of 1 in 69,000. Around 140 deaths would normally be expected in this age-group over this period from all other causes, and so Covid represented roughly an additional 20% increase in risk over this period.

These are observed historical rates in the population, and cannot be quoted as the future risks of getting Covid and dying. In particular the risks of infection will be altered by factors that limit your exposure, and will be expected to drop massively as the epidemic is brought under control.

What about the risks to ‘healthy’ younger people?

The Tables show average risks, but ONS report that 90% of Covid deaths had other pre-existing conditions mentioned on death certificate. In addition, NHS England data on deaths in hospitals shows that, for example, of 196 Covid deaths of people aged 20–39, only 32 had no pre-existing medical condition.

Proportion of Covid deaths in NHS England hospitals with a pre-existing medical condition

Suppose we conservatively assume that -

then any risks faced by those under 50 in the tables above should be divided by a factor of at least 5 to reflect the risks to people without pre-existing medical conditions. For example, this suggests healthy females between 30–34 faced less than a 1 in 350,000 risk of dying from Covid over this period.

Another way of coming to this risk is to see that, of the 29 Covid deaths in this group, we can estimate that around 5 (17%) were of women with no pre-existing health problems. There are 2 million women of this age in England and Wales, and very conservatively assuming that at least 80% of them are healthy, that means there were around 5 Covid deaths out of 1.6 million healthy young women aged between 30–34, a rate of around 1 in 320,000.

It’s worth noting that in 2018, 140 women aged 30–34 died from injuries, so we would expect around 24 over a 9-week period, say at least 20 to ‘healthy’ people. So Covid risk to healthy young women aged 30–34 was around 1/4 of the normal accidental risk to which they were exposed.

In conclusion, healthy children and young adults have been exposed to an extremely small risk during the peak of the epidemic, which would normally be deemed an acceptable part of life.

What about other risk factors?

Apart from age and sex shown in the tables above, research by the ONS suggests that Black, Bangladeshi and Pakistani ethnic groups may have, very roughly, around double the risk of catching and dying from Covid (adjusted for age, sex and deprivation), people living in the most deprived areas had more than double the risk of those in the least deprived areas, and occupations such as security guards, care-home workers, taxi and bus drivers had increased risk. These factors will overlap to some extent. Unfortunately it is not possible at this stage to produce a personalised risk calculator.

What about the risks of dying, if infected?

The fatality rate if you become infected should remain fairly stable over time, and might be very roughly approximated from the analysis above.

Recent ONS surveys estimate that around 7% of the community test positive for having been exposed to the virus. This is likely to be a slight underestimate of the total exposed since it does not include care-homes and hospitals, so assuming around 8% of the population infected, then we should multiply the risks to the population in the tables above by 12 to get the very rough chances of dying if infected.

So for women aged 30–34, the risk of dying if infected would be estimated to be around 12 times ‘1 in 69,000’ which is roughly 1 in 6,000. Again, if healthy, this risk is reduced by a factor of around 5, to around 1 in 30,000. These are very small risks, even if infected.

Since the population risks to the over 45s represents around one month extra risk, then this suggests that the risk of dying, if infected, if over 45 is very roughly the same size, but of course additional to, a normal year’s risk. This supports a previous argument I made back in March. For under 45s, the risk of dying if infected is much less than the normal year’s risk.

What do we mean by ‘the risks of COVID’?

Please permit me a rant. It is vital for journalists and everyone else (including me) to try and avoid phrases like ‘the risks of dying from COVID-19’, as this is deeply ambiguous. The meaning of this phrase crucially depends on the group it refers to, as it could mean-

These are easily confused. An analysis by the Office for National Statistics reported that Black, Asian and minority ethnic (BAME) groups were about twice as likely, after adjusting for some contextual factors, of dying from Covid. But this clearly referred to the population fatality rate — in other words BAME groups had a higher risk of both getting the disease and then dying from it, and an unknown part of this excess risk could come from an increased risk of catching the virus, perhaps through coming in contact with more people in their daily lives. But the BBC 10pm News on May 7th reported that BAME individuals were “90% more likely to die, if they became seriously ill with Covid-19”, which is not at what was being claimed and could be very misleading.

Data sources:

WintonCentre

The Winton Centre for Risk and Evidence Communication is…

WintonCentre

The Winton Centre for Risk and Evidence Communication is hosted within the Department of Pure Mathematics and Mathematical Statistics in the University of Cambridge. Transparent evidence designed to inform, not to persuade.

David Spiegelhalter

Written by

Statistician, communicator about evidence, risk, probability, chance, uncertainty, etc. Chair, Winton Centre for Risk and Evidence Communication, Cambridge.

WintonCentre

The Winton Centre for Risk and Evidence Communication is hosted within the Department of Pure Mathematics and Mathematical Statistics in the University of Cambridge. Transparent evidence designed to inform, not to persuade.

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