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A modelling study published in Royal Society Open Biology looks at the effect of age separation in a population and COVID-19 mortality.
Prof Paul Hunter, Professor in Medicine, UEA, said:
“I am afraid the maths and modelling techniques in this paper are not within my area of expertise and I cannot comment on the appropriateness of the techniques used. However, I am worried about some of the assumptions used in the models which make me question the validity of their conclusions.
“1. The paper says “Mortality rates vary dramatically among age groups and are 0% for 0–14, 0.15% for 15–34, 1% for 35–54 and 24% for ages 55+”. This is way over the top. O’Driscoll and colleagues (Age-specific mortality and immunity patterns of SARS-CoV-2. Nature. 2020 Nov 2:1-9) show that the infection mortality rate in the 55 to 60 age group is less than 1% and in only in the over 75s does the infection fatality rate approach 24%. It is likely that the infection fatality rates have fallen since much of the data was collected in O’Driscoll’s review due to improved treatment.
“2. The other big assumption is “that once an individual becomes symptomatic, he is assumed to be under full quarantine and is therefore removed from the network”. This is almost certainly a false assumption. We have heard a lot in past weeks about the low proportion of people self-isolating when they should be.
“So I personally think we have to be very cautious about accepting the conclusions within this paper whether or not the modelling techniques used are valid and appropriate.”
Prof Sarah Harper, Clore Professor of Gerontology, University of Oxford, said:
“While this is an interesting set of modelling its abstraction for the real-life experience of people of any age makes it difficult to see the relevance for implementation. In particular there are a set of social assumptions which do not fit the reality of modern society.
“Firstly, the model ignores the influence of gender – that at the population level women have a different, and less serious, encounter with COVID. The age brackets should be age 35 men/40 women and 55 men/60 women.
“In addition, they admit that both those 35-54 and 55+ benefitted from reducing contacts in order to reduce the impact of Covid, but then ignore the implications for the younger group.
“The selection of ‘micro-environments’ in which age separation is possible is difficult to justify – grocery shops, theatres and airplane rides. There is an underlying assumption that these are environments in which everyone between 55 and 100 circulate?
“It would be far easier to separate the environment of work – though work as an environment used by anyone over 55 seems to be ignored? Yet in the UK 70% of those aged 55-64 are in work, a large number in health and social care roles. How will these adults be replaced? How will they get an income during this enforced removal?
“Our populations are not as age-segregated as is sometimes thought – not in households and not in wider society. If an age segregation approach is to be taken, an alternative recommendation from the findings of this paper might be that given that those under 35 are known to be more likely to be asymptomatic and thus unknowingly spreading Covid, while those aged over 35 are most vulnerable, perhaps a more effective measure for those who continue to suggest segregating along age lines, would be to separate those aged 15-35 away from mainstream society temporarily and allow everyone over 35 to continue with socially distanced interaction. The question then is whether this would be acceptable in most societies? And if not why would the shutting away of any other age group be acceptable?”
‘Age separation dramatically reduces COVID-19 mortality rate in a computational model of a large population’ by Liron Mizrahi et al. was published in Royal Society Open Biology at 00:01 UK time on Wednesday 11 November 2020.
DOI: 10.1098/rsob.200213
Declared interests
None received.