The effect of mixed vaccination rollout strategy: A modelling study

Area of Science:

• Epidemiology
• Mathematical Modeling
• Public Health

Background:

• Vaccine efficacy (VE) requires long-term population studies beyond initial trials.
• COVID-19 vaccines demonstrate high efficacy against severe disease post-full immunization.
• Understanding real-world vaccine impact is crucial for public health strategies.

Purpose of the Study:

• To assess the impact of COVID-19 vaccination rollout on hospitalization rates.
• To model the performance of different vaccine types against severe disease and transmission.
• To evaluate vaccine effectiveness in a mixed vaccination setting.

Main Methods:

• Utilized an extended Susceptible - Hospitalized - Asymptomatic/mild - Recovered (SHAR) model.
• Incorporated vaccine efficacy data from trials, considering one vs. two doses.
• Simulated vaccine performance for two types: disease-only protection and infection/disease protection.

Main Results:

• Modeled reductions in COVID-19 hospitalizations were observed five months after vaccination rollout began.
• The simulation showed good agreement with empirical data in June 2021.
• Vaccine effectiveness in reducing hospitalizations was demonstrated in the Basque Country, Spain.

Conclusions:

• Mathematical modeling supports the observed reduction in COVID-19 hospitalizations post-vaccination.
• The SHAR model provides a framework for evaluating vaccine impact on population health.
• Real-world data validation is essential for confirming the effectiveness of COVID-19 vaccination programs.