Background: The initial mass vaccination's effectiveness has diminished, necessitating accelerated immunization coverage scaling. China has shifted nucleic acid testing from large-scale to voluntary. This study assesses the effectiveness and cost-effectiveness of different booster vaccination strategies in China. Methods: A dynamic transmission model divided the population into three groups: 0-19, 20-59, and 60+ years. We evaluated the effectiveness and cost-effectiveness of three vaccination strategies based on previous studies and public databases. Three scenarios were modeled and compared to no-continuation-vaccination to calculate averted diseases, deaths, and net benefits. One-way sensitivity analysis and probabilistic sensitivity analysis assessed findings' stability. Results: COVID-19 vaccination had significant health benefits compared to no continuing vaccination. Strategy II (prioritizing vaccinated 20-59-year-olds, then vaccinated 60+ individuals, and finally 0-19-year-olds) was the most cost-effective. Strategy I (prioritizing unvaccinated 60+ individuals, then 20-59, and finally 0-19) prevented the most deaths. Strategy II was the most cost-effective, with a total cost of 93,995,223,462 USD and the highest net benefit of 3,054,475,908,551,960 USD. Strategy II resulted in the highest number of avoided cases across categories, including infected, asymptomatic, mild/moderate, severe, and critical cases. Each strategy's effects on preventing new cases and critical illness were comparable. Sensitivity analyses confirmed the results' reliability. Conclusion: Prioritizing vaccinated 20-59-year-olds, then vaccinated 60+ individuals, and finally 0-19-year-olds was the most effective prevention strategy. The vaccination strategy should be tailored to the pandemic situation and available medical resources for maximum health gains.

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.

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