A modelling study investigating short and medium-term challenges for COVID-19 vaccination: From prioritisation to the relaxation of measures

Abstract

Background: The roll-out of COVID-19 vaccines is a multi-faceted challenge whose performance depends on pace of vaccination, vaccine characteristics and heterogeneities in individual risks. Methods: We developed a mathematical model accounting for the risk of severe disease by age and comorbidity, and transmission dynamics. We compared vaccine prioritisation strategies in the early roll-out stage and quantified the extent to which measures could be relaxed as a function of the vaccine coverage achieved in France. Findings: Prioritizing at-risk individuals reduces morbi-mortality the most if vaccines only reduce severity, but is of less importance if vaccines also substantially reduce infectivity or susceptibility. Age is the most important factor to consider for prioritization; additionally accounting for comorbidities increases the performance of the campaign in a context of scarce resources. Vaccinating 90% of 65 y.o. and 70% of 18À64 y.o. before autumn 2021 with a vaccine that reduces severity by 90% and susceptibility by 80%, we find that control measures reducing transmission rates by 15À27% should be maintained to remain below 1000 daily hospital admissions in France with a highly transmissible variant (basic reproduction number R 0 = 4). Assuming 90% of 65 y.o. are vaccinated, full relaxation of control measures might be achieved with a vaccine coverage of 89À100% in 18À64 y.o or 60À69% of 0À64 y.o. Interpretation: Age and comorbidity-based vaccine prioritization strategies could reduce the burden of the disease. Very high vaccination coverage may be required to completely relax control measures. Vaccination of children, if possible, could lower coverage targets necessary to achieve this objective.

The effect of COVID-19 vaccination in Italy and perspectives for living with the virus

“…However, the high transmissibility of Delta and the imperfect vaccine protection against infection could not be sufficient for a complete return of society to the prepandemic life without the risk of occurrence of further pandemic waves. Our results are in line with previously published modeling studies investigating the interplay between vaccination and relaxation of control measures 28,29,30 .…”

Barrier Gesture Relaxation during Vaccination Campaign in France: Modelling Impact of Waning Immunity

“…Finally, our model, incorporating contact patterns, takes into account both school re-opening and the recovery of on-site work, which leads to increased transmission rates in September. Similar to our findings, a very high vaccination coverage was estimated to be required to allow a complete relaxation of control measures [28], and a high vaccine hesitancy was related to a prolonged need for nonpharmaceutical-interventions [62]. On the other hand, our work highlighted the influence of the immunity duration on the short-term dynamic of the epidemic.…”

“…A French modelling study estimated that it would be necessary to vaccinate 90% of individuals over 65 years old and 89% of the 18-64 year olds before all social distancing measures could be relaxed [28]. This study assumes that immunity does not wane over time, which could lead to an underestimation of these thresholds.…”

Simulation of future COVID-19 epidemic by vaccination coverage scenarios in Japan

“…However, this optimistic projection can be easily dashed when vaccination coverage is low, vaccine efficacy is insufficient, or circulating viruses are more transmissible than expected. A similar conclusion was reached by another simulation study based on situations in France [ 30 ]. Although we performed this study in the context of Japan, the results must have significant implications for other countries as well.…”