London, March 31 : Death rates from COVID-19 vary substantially, ranging from 0.0016 per cent in 0 to 9-year-olds to 7.8 per cent for people aged 80 and above, according to an estimate based on analysis of large number of confirmed cases in mainland China.
The proportion of people with COVID-19 who required hospitalisation also showed sharp increases with age, according to the findings published in the journal The Lancet Infectious Diseases.
Differences in hospitalisation rates increased with age -- with 11.8 per cent of people in their 60s, 16.6 per cent of people in their 70s, and 18.4 per cent of those in their 80s and above estimated to develop symptoms severe enough for hospitalisation.
These hospitalisation rates were higher compared with 0.04 per cent of 10 to 19-year-olds, 1 per cent of people in their 20s, and 3.4 per cent of people aged 30 to 39.
Hospitalisation rates nearly doubled from 4.3 per cent in 40-49-year-olds to 8.2 per cent in 50-59-year olds.
The new analysis also found that the estimated proportion of deaths from both diagnosed cases and from milder, unconfirmed cases is strongly influenced by age.
The death rate from confirmed COVID-19 cases was estimated at 1.38 per cent, while the overall death rate, which includes unconfirmed cases, was estimated at 0.66 per cent.
These rates are slightly lower than some estimates for COVID-19 to date, which had not adjusted for undiagnosed cases or for the number of people in each age group of a population.
The new estimates are based on an analysis of 70,117 laboratory-confirmed and clinically-diagnosed cases in mainland China, combined with 689 positive cases among people evacuated from Wuhan on repatriation flights.
"There might be outlying cases that get a lot of media attention, but our analysis very clearly shows that at aged 50 and over, hospitalisation is much more likely than in those under 50, and a greater proportion of cases are likely to be fatal," said Professor Azra Ghani from Imperial College London.
Previous estimates of deaths from confirmed cases of COVID-19 have ranged from 2 per cent to 8 per cent, while deaths from overall infections have been estimated at 0.2 per cent to 1.6 per cent.
Also, estimates for the proportion of deaths in the oldest age group, the over-80s, have been estimated to be between 8 per cent to 36 per cent.
However, these past estimates had not adjusted for the fact that only people with more severe symptoms are likely to be tested, or people in quarantine following repatriation to other countries, so they did not reflect the true number of cases across populations.
For all the estimates, the researchers assumed that people of all ages are equally likely to become infected, which is consistent with previous studies on respiratory infections.
The average time between the first recorded symptoms and death from COVID-19 was estimated to be 17.8 days.
The authors noted that as the data are from early in the epidemic, more people might die following a longer time lag.
Recovering from the disease is estimated to take slightly longer, with patients being discharged from hospital after an average of 22.6 days.
Most people will recover, even from severe symptoms, the study said.
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