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. 2022 Jan 31;8(1):e35763.
doi: 10.2196/35763.

Has Omicron Changed the Evolution of the Pandemic?

Alexander L Lundberg  1   2 , Ramon Lorenzo-Redondo  3   4 , Egon A Ozer  3   4 , Claudia A Hawkins  3   5 , Judd F Hultquist  3   4 , Sarah B Welch  1   2 , P V Vara Prasad  6 , James F Oehmke  2 , Chad J Achenbach  3   7 , Robert L Murphy  3   7 , Janine I White  1 , Robert J Havey  7   8 , Lori Ann Post  1   2
Affiliations

Has Omicron Changed the Evolution of the Pandemic?

Alexander L Lundberg et al. JMIR Public Health Surveill. .

Abstract

Background: Variants of the SARS-CoV-2 virus carry differential risks to public health. The Omicron (B.1.1.529) variant, first identified in Botswana on November 11, 2021, has spread globally faster than any previous variant of concern. Understanding the transmissibility of Omicron is vital in the development of public health policy.

Objective: The aim of this study is to compare SARS-CoV-2 outbreaks driven by Omicron to those driven by prior variants of concern in terms of both the speed and magnitude of an outbreak.

Methods: We analyzed trends in outbreaks by variant of concern with validated surveillance metrics in several southern African countries. The region offers an ideal setting for a natural experiment given that most outbreaks thus far have been driven primarily by a single variant at a time. With a daily longitudinal data set of new infections, total vaccinations, and cumulative infections in countries in sub-Saharan Africa, we estimated how the emergence of Omicron has altered the trajectory of SARS-CoV-2 outbreaks. We used the Arellano-Bond method to estimate regression coefficients from a dynamic panel model, in which new infections are a function of infections yesterday and last week. We controlled for vaccinations and prior infections in the population. To test whether Omicron has changed the average trajectory of a SARS-CoV-2 outbreak, we included an interaction between an indicator variable for the emergence of Omicron and lagged infections.

Results: The observed Omicron outbreaks in this study reach the outbreak threshold within 5-10 days after first detection, whereas other variants of concern have taken at least 14 days and up to as many as 35 days. The Omicron outbreaks also reach peak rates of new cases that are roughly 1.5-2 times those of prior variants of concern. Dynamic panel regression estimates confirm Omicron has created a statistically significant shift in viral spread.

Conclusions: The transmissibility of Omicron is markedly higher than prior variants of concern. At the population level, the Omicron outbreaks occurred more quickly and with larger magnitude, despite substantial increases in vaccinations and prior infections, which should have otherwise reduced susceptibility to new infections. Unless public health policies are substantially altered, Omicron outbreaks in other countries are likely to occur with little warning.

Keywords: Beta; COVID-19; Delta; Omicron; SARS-CoV-2; VOC; epidemiology; pandemic; public health; public health surveillance; sub-Saharan Africa; variant of concern.

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Conflict of interest statement

Conflicts of Interest: None declared.

Figures

Figure 1
Figure 1
First sub-Saharan countries to experience an Omicron outbreak.
Figure 2
Figure 2
A screen capture of a dynamic map of transmission of the SARS-CoV-2 pandemic through Africa after the Omicron variant was identified. Full video can be viewed here: [44].
Figure 3
Figure 3
Botswana outbreaks by variant of concern.
Figure 4
Figure 4
Eswatini outbreaks by variant of concern.
Figure 5
Figure 5
Gabon outbreaks by variant of concern.
Figure 6
Figure 6
Lesotho outbreaks by variant of concern.
Figure 7
Figure 7
Namibia outbreaks by variant of concern.
Figure 8
Figure 8
South Africa outbreaks by variant of concern.
Figure 9
Figure 9
Zambia outbreaks by variant of concern.
Figure 10
Figure 10
Zimbabwe outbreaks by variant of concern.
See this image and copyright information in PMC

References

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