I have some friends in their mid-70s who have only left their home a handful of times over the last three months only for bare essentials because of their dread of becoming infected with COVID. In their minds, contracting the virus is tantamount to a virtual death sentence. So, what do we know about the odds of surviving a COVID infection, especially if you are somewhat older?
We have known for some time that the likely “infection fatality rate,” that is, the percentage of people who will die from an infection, was around 1%. Even the doomsday models, such as the now discredited Imperial College model, only used a 1.3% assumption. There has been a lot of discussion on social media and some in the media about much higher numbers based on the “case infection rates” (the number of fatalities/the number of confirmed cases) some countries are seeing. For example, in Italy, over 14% of those confirmed to have the virus have died. But we know that many more people have been infected with the virus than have been confirmed by a test. And, of course, the outcomes will vary from one country to another based on the quality of their healthcare system. In Germany, for example, the case fatality rate currently is 4.6%.
As antibody testing has become more widespread, various studies have begun revising the estimated infection fatality rate down as we have learned more about how widespread the disease has already become, thus increasing the denominator of the fraction. This week, the CDC announced its best estimate was that about 0.4% with symptoms would die and that about 35% of those infected do not have any symptoms. That would imply an IFR of under .3%. That compares to the regular flu at about .1%
So, we start with the general proposition that the data indicates that the average person is more than 99% likely to survive a COVID infection. But what about my friends in the mid-70s? What might their odds be?
The new CDC’s estimates put the range for those over 65 will die from a symptomatic infection at .06%-3.2%. In other words, the CDC estimates that 96.6% to 99.4% of those over 65 will survive a symptomatic infection.
The only data with fatalities and confirmed cases broken down by age I could find was for New York City. As of May 21, here was the breakdown:
So, in New York City, about 65% of those over 75 who were confirmed to have COVID-19 recovered from the disease. However, it is likely that both the numerator (the number of fatalities) and the denominator (the number of cases) are both understated.
The number of deaths is understated because there has been limited testing, especially early in the onset. As a result, some people unquestionably died with the disease, but it was not listed as the cause of death. This NY Times article estimates that about 4,600 COVID-related deaths in NYC have not been reported. That seems a little unlikely to me, but let’s use their number as the numerator for argument’s sake.
Trying to estimate the denominator becomes a little trickier. The only data we have that gives any glimpse into this question is an antibody study New York performed near the end of April. According to that study about 20% of New York City’s population had been infected with the virus. However, the confirmed cases are only about 2.5% of the City’s population. This would imply that there were about eight times more people with actual infected cases than had been confirmed. Here is what the age breakdown looks like if we make both of those adjustments to the NYC data:
Based on these assumptions the IFR comes out at about 1.3% for all age groups, three times higher than the CDC’s latest estimate. When we look at the age breakdown, well over 99% of everyone under the age of 65 survived. Also, 97% of those 65-74 survived and 93% of those 75+ survived.1
Of course, these are averages. The risk for specific individuals varies and for some it varies dramatically from the average based on their underlying health condition. Factors such as an existing respiratory illness, a compromised immune system and obesity could well make a COVID infection the virtual death sentence my friends fear. Each person should consult their doctor about their individual circumstances.
But the data is clear that the overwhelming majority of healthy people who contract a COVID infection will recover, even if they are somewhat older.
1 New York has not released all the demographic details on the antibody tests, but Governor Cuomo did show a slide in one of his presentations that showed the antibody tests results by age. It was fairly uniform across the age brackets with slightly more cases showing up in the middle age brackets. I have posted the spreadsheet I used for this calculation [here]. You can adjust the various assumptions I have outlined here to make your own estimates.