Three UF researchers projected how four different scenarios may play out between December 2021 and February 2022 given varying parameters of transmission, immune escape, and disease severity. (Immune escape refers to the ability of the omicron variant to evade immunity due to natural infection or vaccination.)
Because the omicron variant is so new, and some of its properties are not well known, the researchers adjusted these three parameters to explore various outcomes. All four projections are available in this report and they all agree that the omicron wave will grow slowly through December, rapidly in January, and peak in February
Most likely scenario
The most likely scenario may be the third one in their report, which assumes that the omicron variant will have a high transmission advantage, moderate immune escape, but low disease severity.
The figure above shows the reported and modeled cases per day in Florida through May 2022. The projected winter/spring surge reflects the increased infectiousness and immune escape of the omicron variant. The black line shows past actual reported COVID-19 cases, and the yellow line shows the projected reported cases per day.
The figure above shows the projected deaths of COVID-19 that are expected to be reported per day in Florida through May 2022. The winter/spring small surge reflects the increased infectiousness and immune escape of the omicron variant, and the expected decreased severity of disease produced. The black line shows past actual reported deaths due to COVID-19, and the red line shows the projected reported deaths per day.
The figure above shows how omicron (purple) is expected to displace delta (teal) as the dominant strain in Florida beginning in December 2021. Omicron is expected to be the dominant variant in Florida by early January 2022.
The figure above shows the total number modeled infections per day, both asymptomatic and symptomatic. The number of projected infections is much larger than the number of reported cases because many infections are not reported, especially if they are asymptomatic or mild. Omicron is likely to typically cause less severe infections than delta (though hospitalizations and deaths will still occur), and fewer of the infections it causes are expected to be reported.
Rt, known as the effective reproduction number at time t, varies over time and expresses how many people become infected from a single index case at that time. In order for an epidemic wave to pass its peak and begin to decline, Rt must fall below 1, which means that each infected person transmits the virus to fewer than one additional person. Rt increases again at the end of the simulation (far right) because the researchers assume that people will relax the precautions they took during the initial onset of the omicron wave and also because SARS-CoV-2 transmission tends to increase in the summer in Florida.
Less likely, but possible, scenarios
Other scenarios can be explored in the full report.
Acknowledgments: Figures and associated reported created by Thomas Hladish, research scientist in the Department of Biology at UF; Alexander Pillai, research assistant in the Department of Biology at UF; and Ira Longini, Jr., professor in the Department of Biostatistics at UF.
This work was supported by the UF Emerging Pathogens Institute, National Institutes of Health, and the World Health Organization.
