Age-stratified Infection Probabilities Combined with Quarantine-Modified SEIR Model in the Needs Assessments for COVID-19 (Preprint)

BACKGROUND Classic compartmental models such as SEIR all have the weakness of assuming a homogenous population, where everyone has an equal chance of getting infected and dying. Starting in Hubei, China in December 2019, COVID-19 rapidly spread throughout the world and has been declared a pandemic. Based on data from Hubei, infection and death distributions vary with age. To control the spread of the disease, various preventive and control measures such as community quarantine and social distancing have been widely used. OBJECTIVE We now develop a model where age is a factor, considering the study area's age stratification. Additionally, we want to account for the effects of quarantine on the SEIR model. METHODS We use the age-stratified COVID-19 infection and death distributions from Hubei, China (more than 44,672 infectious as of February 11, 2020) as an estimate or proxy for a study area's infection and mortality probabilities at each age group. We then apply these probabilities into the actual age-stratified population of Quezon City, Philippines, to predict infectious individuals and deaths at peak. Testing with different countries shows the predicted infectious skewing with the country's median age and age stratification, as expected. We added a Q parameter to the SEIR model to include the effects of quarantine (Q-SEIR). RESULTS The projections from the age-stratified probabilities give much lower predicted incidences of infection than the Q-SEIR model. As expected, quarantine tends to delay the peaks for both Exposed and Infectious, and to 'flatten' the curve or lower the predicted values for each compartment. These two estimates were used as a range to inform the local government's planning and response to the COVID-19 threat. CONCLUSIONS Age-stratification combined with a quarantine-modified model has good qualitative agreement with observations on infections, and specially death rates. That younger populations will have lower death rates due to Covid-19 is a fair expectation for a disease where most fatalities are in the higher age groups. CLINICALTRIAL