COVID-19 Attack Rates by Vaccination Status and Age
COVID-19 vaccinations are preventing severe illness and deaths among Virginians who have received their shots. At the same time, the highly contagious Delta variant has become the main strain of the virus in Virginia and the United States. Many factors affect the direction the pandemic takes, including new variants that emerge and their effect on vaccine effectiveness, vaccination rates, seasonal changes, and the acceptance and use of other mitigation strategies, like physical distancing and community masking. Some factors reduce the spread of the virus, while others increase it. As these factors interact, trends in how the virus spreads and who is most affected can change as well.
Most recently, there has been a shift in health outcomes by age group. COVID-19 causes more severe disease in older age groups. Fortunately, high rates of vaccination among Virginians 65 and older means a reduced risk of severe COVID-19 disease. However, hospitalization rates are now increasing in younger age groups that have lower vaccination rates. 83% of those 65+ have been vaccinated, compared to 18% of those under the age of 18. The upward trend in hospitalizations among younger age groups can be observed in figure 1.1 below:
Rate ratios are used in epidemiology to compare the severity of disease across different groups. They take into account differences in the groups’ characteristics, such as age. Rate ratios are calculated as follows:
