Different vaccination strategies for preventing coronavirus disease 2019 in Kenya: A dynamic modelling study of health impact and cost-effectiveness

Background: Vaccination can significantly reduce the health impact and economic burden of coronavirus disease 2019 (COVID-19), but vaccination levels for COVID-19 in most African countries lag far behind global averages. We assessed the cost-effectiveness of different COVID-19 vaccination strategies in Kenya and determined the optimal vaccination strategy. Methods: Using a dynamic transmission model, we divided the population into three groups: 0-18 years, 19-58 years and 58+ years. We assessed the effectiveness and cost-effectiveness of three vaccination strategies at different numbers of daily vaccinations based on previous studies and public databases. Nine scenarios were modeled and compared to no-continuation-vaccination to calculate the number of averted diseases, averted deaths, and net benefits of different vaccination strategies. One-way sensitivity analysis and probabilistic sensitivity analysis were conducted to assess the stability of our findings. Results: Compared to no-continuation-vaccination for various vaccination scenarios, all vaccination strategies were found to be effective and cost-saving. The incremental net benefit ranged from 0.235 billion USD to 2.305 billion USD, and prioritizing vaccination boosters for individuals aged 19-58 was identified as the most cost-effective option. On the other hand, prioritizing vaccination for the unvaccinated population aged 58 and above could potentially reduce COVID-19 related deaths by 1.59%-56.60%, which was the most effective approach in avoiding cause-specific deaths. However, all vaccination strategies were found to be ineffective in controlling the infection trend when compared to no intervention under different vaccination scenarios, with only 474,318-5,306,865 infections potentially being prevented. Conclusion: Timely and widespread vaccination against COVID-19 in Kenya is effective and cost-effective, a specific vaccination strategy should be selected based on decision-making needs. Priority vaccination for the elderly without vaccination may be more cost-effective compared with other vaccination strategies.