Impact of vaccination and non-pharmaceutical interventions on SARS-CoV-2 dynamics in Switzerland

Background: As vaccination coverage against SARS-CoV-2 increases amidst the emergence and spread of more infectious and potentially more deadly viral variants, decisions on timing and extent of relaxing effective, but unsustainable, non-pharmaceutical interventions (NPIs) need to be made. Methods: An individual-based transmission model of SARS-CoV-2 dynamics, OpenCOVID, was developed to compare the impact of various vaccination and NPI strategies on the COVID-19 epidemic in Switzerland. OpenCOVID uses the Oxford Containment Health Index (OCHI) to quantify the stringency of NPIs. Results: Even if NPIs in place in March 2021 were to be maintained and the vaccine campaign rollout rapidly scaled-up, a 'third wave' was predicted. However, we find a cautious phased relaxation can substantially reduce population-level morbidity and mortality. We find that faster vaccination campaign can offset the size of such a wave, allowing more flexibility for NPI to be relaxed sooner. Model outcomes were most sensitive to the level of infectiousness of variants of concern observed in Switzerland. Conclusion: A rapid vaccination rollout can allow the sooner relaxation of NPIs, however ongoing surveillance of and swift responses to emerging viral variants is of utmost importance for epidemic control.

Automated summary

The research suggests that even with current NPI measures and rapidly scaled-up vaccine campaigns, a new wave of the epidemic is still predicted. However, a cautious phased relaxation of measures can significantly reduce population morbidity and mortality, while a faster vaccine rollout can offset the impact of such a wave and allow for earlier relaxation of NPIs. Ongoing monitoring and rapid responses to emerging viral variants are crucial for epidemic control.