@article {CAETANO2022,
	title = {Measuring the impact of COVID-19 vaccination and immunity waning: a modelling study for Portugal},
	journal = {Vaccine},
	year = {2022},
	note = {n/a},
	abstract = {<p>Vaccination strategies to control COVID-19 have been ongoing worldwide since the end of 2020. Understanding their possible effect is key to prevent future disease spread. Using a modelling approach, this study intends to measure the impact of the COVID-19 Portuguese vaccination strategy on the effective reproduction number and explore three scenarios for vaccine effectiveness waning. Namely, the no-immunity-loss, 1-year and 3-years of immunity duration scenarios. We adapted an age-structured SEIR deterministic model and used Portuguese hospitalisation data for the model calibration. Results show that, although the Portuguese vaccination plan had a substantial impact in reducing overall transmission, it might not be sufficient to control disease spread. A significant vaccination coverage of those above 5 years old, a vaccine effectiveness against disease of at least 80\% and softer non-pharmaceutical interventions (NPIs), such as mask usage and social distancing, would be necessary to control disease spread in the worst scenario considered. The immunity duration scenario of 1-year displays a resurgence of COVID-19 hospitalisations by the end of 2021, the same is observed in 3-year scenario although with a lower magnitude. The no-immunity-loss scenario presents a low increase in hospitalisations. In both the 1-year and 3-year scenarios, a vaccination boost of those above 65 years old would result in a 53\% and 38\% peak reduction of non-ICU hospitalisations, respectively. These results suggest that NPIs should not be fully phased-out but instead be combined with a fast booster vaccination strategy to reduce healthcare burden.</p>
},
	keywords = {compartmental models, COVID-19, epidemiology, SEIR model, vaccination, vaccine effectiveness waning},
	issn = {0264-410X},
	doi = {https://doi.org/10.1016/j.vaccine.2022.10.007},
	url = {https://www.sciencedirect.com/science/article/pii/S0264410X22012555},
	author = {Constantino Caetano and Maria {Lu{\'\i}sa Morgado} and Paula Patr{\'\i}cio and Andreia Leite and Ausenda Machado and Andr{\'e} Torres and Jo{\~a}o Freitas Pereira and S{\'o}nia Namorado and Ana Sottomayor and Andr{\'e} Peralta-Santos and Baltazar Nunes}
}
