The CDC report is not a prediction or forecast. Rather, it is a set of four scenarios based on modeling of the pandemic, using different assumptions about vaccination rates, vaccine efficacy and precautions against transmission. Each scenario shows an epidemic curve in which the national increase in cases that began in early March hits a peak and then plummets in late spring, leading to a dramatically improved viral landscape this summer. In the less optimistic scenarios, hospitalization numbers will vary significantly from state to state. Under the most optimistic scenario, deaths from covid-19, the disease caused by the coronavirus, could drop into the low 100s per week in August and into the “tens” per week in September, according to Justin Lessler, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health and one of the paper’s senior authors. Currently, more than 4,000 people a week are dying of the disease, and about 578,000 people in the United States have died of covid-19 since the start of the pandemic. That model includes an assumption that 90 percent of those eligible for vaccine would get a shot, which Lessler acknowledged “may be on the optimistic side given rates of vaccine refusal in some areas.”