Estimating Prevalence and time Course of Sars-Cov-2 Based on new Hospital Admissions and PCR Tests: Relevance to Vaccination Program Tactical Planning

Abstract

Data posted in the COVID 19 tracking website for RT-PCR (PCR) results and hospital admissions are used to estimate the prevalence of the SARS-CoV-2 pandemic in the United States (1). Hospital admissions mitigate positive sampling bias in PCR tests due to their initially limited test numbers and application as a diagnostic, instead of a surveying tool. As of July 31, the United States' cumulative recovered population is estimated at 47% or 155 million. The remaining susceptible population is 53%, or 47% excepting the 6% infectious population. The estimated mortality rate of the cumulative recovered population is 0.09% death per case. New York and Massachusetts show SARS-CoV-2 prevalence of 87% and 55%, respectively. Likewise, each state exhibits relatively low current positive PCR results at 1 % and 1.7%. Also, these states show about twice the mortality rate of the nation. Florida, California, and Texas showed recovered population percent around 40%, higher current PCR positive test results ranging from 7% to 13%. A higher recovered population mitigates the current positive value attainable by limiting the infectivity rate Re. This approach provides an alternate source of information on the pandemic's full time course since the serological testing only views a narrow time slice of its history due to the transient nature of the antibody response and its graduated expression dependency on the severity of the disease. The deficiency of serological testing to estimate the recovered population is made even more acute due to the large proportion of asymptomatic and sub-clinical cases in the COVID-19 pandemic