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. 2021 Jan 22;70(3):95–99. doi: 10.15585/mmwr.mm7003e2

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The figure is a histogram, an epidemiologic curve, showing simulated case incidence trajectories of current SARS-CoV-2 variants and the B.1.1.7 variant, assuming community vaccination and initial Rt = 1.1 (A) or initial Rt = 0.9 (B) for current variants, in the United States, during January 2021. — Simulated case incidence trajectories* of current SARS-CoV-2 variants and the B.1.1.7 variant,^† assuming community vaccination^§ and initial R_t = 1.1 (A) or initial R_t = 0.9 (B) for current variants — United States, January–April 2021

Abbreviation: R_t = time-varying reproductive number.

* For all simulations, it was assumed that the reporting rate was 25% and that persons who were seropositive or infected within the simulation became immune. The simulation was initialized with 60 reported cases of SARS-CoV-2 infection per 100,000 persons (approximately 200,000 cases per day in the U.S. population) on January 1, 2021. Bands represent simulations with 10%–30% population-level immunity as of January 1, 2021.

^† Initial B.1.1.7 prevalence is assumed to be 0.5% among all infections and B.1.1.7 is assumed to be 50% more transmissible than current variants.

^§ For vaccination, it was assumed that 300 doses were administered per 100,000 persons per day (approximately 1 million doses per day in the U.S. population) beginning January 1, 2021, that 2 doses achieved 95% immunity against infection, and that there was a 14-day delay between vaccination and protection.