Can a vaccine-led approach end the NSW outbreak in 100 days, or at least substantially reduce morbidity and mortality? (preprint)

ABSTRACT

Abstract Background and Aims The New South Wales (NSW) COVID-19 outbreak is at 478 daily cases on August 16, 2021. Our aims were to 1) estimate the time required to reach ≤5 cases per day under three lockdown strengths (weak, moderate, strong), and four vaccination rollouts (a) per the original plan, (b) prioritizing essential workers, (c) b plus rapid vaccination of 25% of <60-year-olds with AstraZeneca (AZ25), and (d) b plus rapid vaccination of 50% of <60-year-olds with AstraZeneca (AZ50). 2) estimate the number of cases, hospitalizations, and deaths in the 100 days after 1/August for the 12 scenarios. Methods An agent-based model was adapted to NSW and the Delta variant. Hospitalization and mortality rates for unvaccinated COVID-19 infections were doubled given the virulence of Delta. Results The business-as-usual rollout fully vaccinates 50%, 70% and 80% of >16-year-olds by 10/Oct, 21/Nov, and 28/Dec, respectively. This reduced to 1/Oct, 30/Oct, and 22/Nov for the fastest (AZ50) rollout. A strong lockdown with a rapid vaccine rollout was the fastest to reach ≤5 cases (14-day average), with a median of 78 days (90% Uncertainty interval 61 - 103) or 18/Oct, compared to 207 days (166 - 254) or 24/Feb for a weak lockdown with no rollout acceleration. Increased lockdown strength had more impact than rollout acceleration. Under the AZ25 vaccination scenario, there were 1,440 (90% UI 262 - 10,600 deaths in the first 100 days of cases under a weak lockdown, compared to 71 (90% UI 26 - 178) under a strong lockdown scenario. Conclusion NSW will likely achieve 70% vaccination of >16-year-olds before reaching ≤5 daily cases. Accelerating the vaccine rollout is important for the medium-term, but in the short-term increased restriction strength was more effective at reducing caseload (and subsequently mortality and hospitalisation) than accelerating the vaccine rollout.