Analysis: City’s COVID-19 data surprises

Analysis: City’s COVID-19 data surprises
An illustration of the COVID-19 virus. (Image/Centers for Disease Control and Prevention)

By Denise Dunbar

Data released by the Alexandria Health Department on Sept. 10 reveals a close correlation between the percentage of overall COVID-19 cases by age group in July and August and an age group’s percentage of the overall population. For instance, 35 to 44-year-olds make up 18.5% of Alexandria’s population, and 20.7% of COVID-19 cases in July and August came from this age group.

But further analysis of the data reveals that age, rather than vaccine rate, is more closely correlated with the percentage of each age group that contracted COVID-19 in July and August. For instance, the 18 to 24 age group and 75 plus age groups both had vaccination rates of more than 80% – at 80.6% and 86.6% respectively – yet people 18 to 24 were almost six times more likely to have contracted COVID-19 in July or August than those 75 and older.

The Times used the total population number of 159,428 and the percentage breakout listed in the ADH data to arrive at a specific number of people for each population group. For instance, the data states that 7.5% of city residents are between 65 and 74 years old. This means there are 11,957 people in this age group. Taking the actual number of people who contracted COVID-19 in July and August, it is possible to arrive at a percentage of each age group that got the disease in those two months.

Of all age groups eligible to receive the COVID-19 vaccine, which is anyone who is 12 and older, the group with by far the lowest vaccine rate is 25 to 34-year-olds, of which only 59% have received at least one dose of the vaccine, according to AHD. Yet this group’s rate of infection in July and August was .83%, well behind the 1.14% rate of 18- to 24-year-olds, even though 80.6% of this younger group is at least partially vaccinated.

Two groups had an identical .72% infection rate per person in July and August: those age 0 to 11 and those age 35 to 44. Yet no one in the age 0 to 11 age group has been vaccinated, while 73.3% of those who are 35 to 44 have received the vaccine, according to AHD data.

It’s true that the percentage of people in all age groups who contracted COVID-19 in July and August is small, with the highest group at just over a 1% infection rate. And while any deaths are too many, just two Alexandria residents of any age group died from COVID-19 during those two months. But the raw number of people who got sick in July and August was more than 200 in two groups: 280 people ages 25 to 34 and 211 people ages 35 to 44 contracted COVID-19 in July or August.

By far the highest vaccination rates in the city were for children ages 12 to 15, at 94.3%, and those 16 to 17 years old, at 92.9%. These numbers indicate that parents are getting their children vaccinated, whether or not they get the vaccine themselves.

The three age groups with the highest infection rates per person are 16 to 17, 18 to 24 and 25 to 34. This overall age group of 16 to 34 includes older teenagers and young adults, including college students. This age group has long been associated with higher-risk behavior; for instance, according to, those aged 16 to 35 pay higher car insurance rates than older drivers. The age of these residents could have been a factor in their higher COVID-19 infection rates from the highly contagious Delta variant that spread in July and August.

There were significantly fewer infections per resident in July and August in Alexandria’s oldest age groups than in younger groups, and the infection rate declines with each successively older category. Those 45 to 54 had an infection rate per person in July and August of .48%, those 55 to 64 had an infection rate of .42%, those 65 to 74 had a rate of .26% and those 75 and older had a rate of .20%.