Background: The increasing vaccination coverage against SARS-CoV-2 enabled relaxation of lockdowns in many countries. The public health authorities are seeking recommendations on the continuation of physical distancing measures during ongoing vaccination rollouts. Compliance with these measures is waning while more transmissible virus variants have emerged.
Methods: We used a SARS-CoV-2 transmission model to investigate the feedback between compliance, infection incidence, and vaccination coverage. We quantified our findings in terms of cumulative numbers of new infections three and six months after the start of vaccination.
Results: Our results suggest that the combination of fast waning compliance in non-vaccinated individuals, low compliance in vaccinated individuals, low vaccine efficacy against infection and more transmissible virus variants may result in a higher cumulative number of new infections than in a situation without vaccination. These adverse effects can be alleviated by deploying behavioural interventions that should preferably target both vaccinated and non-vaccinated individuals. The choice of the most appropriate intervention depends on vaccination rate and vaccine efficacy again infection.
Conclusion: Supplementary behavioural interventions aiming to boost compliance to physical distancing measures can improve the outcome of SARS-CoV-2 vaccination programmes, until vaccination coverage is suffciently high. For optimal results, these interventions should be selected based on the vaccine efficacy against infection and expected vaccination rate.