Objective: Omicron (B.1.1.529) variant has caused global concern. Previous studies have shown that the variant has enhanced immune evasion ability and transmissibility, and reduced severity. Methods: In this work, we develop a mathematical model with time-varying transmission rate, vaccination and immune evasion. We fit model to reported case and death data, up to Feb 6, 2022 to estimate the  transmissibility and infection fatality ratio of Omicron variant in South Africa. Results: We found that the high relative transmissibility of Omicron variant is mainly due to its immune evasion ability while the infection fatality rate is substantially decreased. The reduction in the infection fatality rate is about 78.7% (95% confidence interval: 66.9%, 85%). Conclusion: Based on data in South Africa and mathematical modelling, we found that the Omicron variant is highly transmissible but with significantly lower infection fatality rate compared to previous variant of SARS-COV-2.

Fuente: International Journal of Infectious Diseases
Available online 21 April 2022