TL;DR Our estimation of young adult mortality could be biased because of longer survival time before death in ICU and triage.
The data from Asia is that the mortality of young adults between 20-39 is like 0.2 per cent. This sometimes contradicts claims from the ground in Italy, like:
"There are many young people in intensive care, so we dispelled a 'myth', for which Coronavirus is a disease that affects only the elderly: stay at home, who can, don't go out, maybe just so we could come out! There will be a happy ending only if we respect the rules. So stay at home, respect the safety distances ”
However, Italy still almost didn’t report deaths of people below 50. The main question is: could it be taken as evidence of the low young adult's mortality in the situation after the medicine collapse?
The lack of reports of the death of young adults could have 3 possible explanations which need additional verification:
1) Better survival on the ventilator. Young adults survive better if they put on the ventilator. I don’t know how many young adults are currently on the ventilator. However, if there will be a shortage of ventilators, the mortality of young adults will jump.
2) Better triage. Young adults are getting better triage. Because young adults seem to survive better on ventilators and also are a more valuable part of society, they are given ventilators, and older people are turned off if there is a shortage of ventilators. It was reported that in Italy they had to turn off 40 years old people to save 30 years old ones (I lost the link, but will add when will find).
3) A longer time before death. Some young adults could survive for a much longer time on the ventilator and will die anyway. Maybe they can survive 6-8 weeks on the ventilator but will die eventually. In that case, we are just not starting to see these deaths, as the jump of infections started around mid-January, or around 8 weeks ago. In China, there are still 3000 people in serious condition, and as the peak of infections was at the beginning of February, most of them were diagnosed more than a month ago.
The main question here is the age of people in ICU, not age of deaths, as younger people may live longer in ICU. Some data points: Half of the Dutch patients in ICU are below 50, and 16 years boy is in a coma.