We know that once infected, people of older ages are disproportionately susceptible to severe illness and death from COVID-19, and data from countries around the world consistently bear this out. Interestingly, however, the rate at which different ages are infected can vary significantly from country to country.
COVID-19鈥檚 infection rate 鈥 or attack rate 鈥 is a key variable for understanding the impact of the pandemic. After all, widespread infection is one of only two ways (the other being vaccination) that we will achieve some form of lasting herd immunity 鈥 assuming such immunity is achievable.
For (re)insurers tasked with translating impacts of the pandemic from a general population to an insured population, it is important to know how infection rates vary by age (along with socioeconomic differences in infection rates, the severity of infection, and other related factors). While data on infection rates by age is limited, country-by-country comparisons can be illuminating.
Consider the chart below, which shows estimates of the infection rate across ages 20 to 80 in Spain and the U.K. The first is taken from the June 3 preliminary report on the Spain Ministry of Health鈥檚 seroprevalence study, looking at the presence of COVID-19 antibodies in a sample of more than 60,000 individuals intended to broadly reflect the entire Spanish population. The second is from the June 22 鈥漬owcast鈥 from the MRC Biostatistics Unit at the University of Cambridge, which is informed in part by data from England鈥檚 National Health Service Blood Transfusion service on antibody testing.
There is a clear difference in the shape of infection rates by age from these two sources. Whereas infection rates in Spain generally increase with age to a peak for people in their early 70s, the opposite is seen in England, with infection rates decreasing with age to a low for people in their early 70s.
Some contributing factors to consider:
However, even allowing for these factors, the difference in shape between these two estimates is remarkable.
COVID-19 infection rates can vary significantly by age, and the age-shape can vary significantly by country. It is important to recognize that the results shown here are estimates of pandemic experience in Spain and England so far, and trends in infection rates by age may look very different in the future. This is a reminder that care needs to be taken before applying results derived from one population to another. Global insurers, in particular, will need to bear this in mind when trying to estimate the impact of the pandemic on their insured books.
