Fairfax Cases by Age, August 2021

I have now started tabulating the case data for Fairfax County broken done into 4 age groups, under 18, 18-49, 50-65, and 65+. By comparing the recent case data for the last 6 days with the total case data from March 2020, you can see some significant changes that might help explain recent trends in Fairfax County. The Table below summarizes the number of cases in each category, and the corresponding percent of cases.

The new data show a clear trend in age distribution relative to the total cases during the whole pandemic, namely, recent new cases are shifting away from the oldest age groups and towards the youngest. The data for the last 6 days shows a large 73 percent increase in cases relative to the pandemic average for our youngest group under 18, namely, from 15 to 26 percent of the total. Slightly more than half the cases throughout have come from the 18-49 age group. By contrast, the oldest age groups 50-64 and 65+ show a 25 percent or more decreases over the last 6 days in their respective pandemic average contributions of 20 and 10 percent of the total.

This trend helps explain why the hospitalization and death rates have remained low in Fairfax County. Cases are increasing most rapidly in younger people, especially children, who generally do not get as sick as older people (Note: NO ONE under 18 had died in Fairfax County, in spite of over 12000 cases!). The one single death in the last 6 days in Fairfax County was from the 65+ group, which is responsible for most of the deaths here, 82 percent in the overall pandemic. I expect the trend to continue such that the few people who will die of COVID-19 in the next few weeks in Fairfax will be predominantly in the 65+ age group.

Some guesswork

The decrease in case rates for those 50 or older may be due to the fact that the older groups are highly vaccinated in Fairfax County, leading to a lower fraction of cases than in the previous stages of the pandemic. The low hospitalization and death rates in Fairfax likely correlate with both the lower case rates in these older groups and their higher vaccination rate, which reduces the severity of the illness for these groups..

Finally, I would like to make a comment regarding my comparison yesterday of Fairfax and Florida, the latter having a death rate per capita for the last week nearly 50 times that in Fairfax. I am guessing that it mainly has been older people in Florida who have contributed to the higher death rate. But why is the rate in Florida SO MUCH HIGHER? If there has been much less masking and distancing in Florida than Fairfax, then older people there would have been exposed to much higher viral loads with Delta, and thus would be much more likely to have severe disease (severity correlates with viral load–the number of virus particles you take in). I do not have age-based data for Florida. Maybe ALL age groups in Florida, where masking is less socially acceptable than in Fairfax, are getting much higher viral loads, leading to more severe disease across the board in all age groups. For whatever reason, death rates are strikingly higher in Florida than in Fairfax. That is a simple but tragic fact.

In Fairfax, 1 in 9 people over 65 who got COVID-19 died from it (945 deaths out of 8214 cases). It is very dangerous to get COVID-19 if you are over 65. Vaccines will cut the danger, but I have not seen data that quantify it yet for the recent Delta surge. But if you take the 47 cases for the 65+ age group in Fairfax in the last 6 days and say that 1 in 9 will die, that would be a death rate of around 5 per week, whereas we are only having around a total of 1 death per week now. So the odds are better than before. We should wait a few weeks to see, but let’s just guess that the death rate of vaccinated people over 65 in Fairfax my be much lower, closer to 1 in 50. That would correlate with 1 death per week if the case rate for 65+ in Fairfax stayed around 50 per week. I would guess that it is safer to be over 65 with COVID-19 in Fairfax than in Florida since our older people are probably getting much lower viral loads than older people in Florida due to better masking and other precautions.