Mobility during lockdowns: A comparison of VIC and NSW outbreaks
Lockdowns have been used by a number of Australian state governments as a vital tool in suppressing COVID-19 outbreaks. The general goal of COVID outbreak management is to return to a situation of zero community transmission. However the specific definition of a “lockdown” varies between states, with some jurisdictions enforcing stricter social and commercial restrictions and other states preferring a lighter approach.
The SARS-CoV-2 virus spreads primarily through human contact. Thus social distancing and limiting human movements is the key mechanism employed successfully by lockdown strategies. A number of organisations such as Google, Apple and CityMapper provide publicly available datasets that track metrics related to human movements. These datasets can be used to compare the effects of lockdown strategies between states and cities and highlight how differences in local policy may influence overall human mobility and subsequently the effectiveness of the lockdown.
Figure 1 (Tableau) presents data from the Google Mobility index for jurisdictions in Sydney [NSW] compared Metropolitan Melbourne [VIC] (see Sources for link to notebook containing specific LGAs included in the VIC vs NSW definitions). We can see a complex evolution over time as jurisdictions enter and emerge from lockdown conditions. Noticeable trends are present for the 2020 “Second Wave” Victorian lockdown, and subsequent short-term “circuit-breaker” lockdowns employed to suppress outbreaks.
Mobility for Retail and Recreation returned to near-baseline levels for NSW, and a maximum of -7% below baseline for VIC. Public Transit remains suppressed at levels 20% to 30% below pre-COVID for both VIC and NSW, despite Sydney not undergoing a prolonged lockdown in 2020. Workplace attendance remained suppressed at 9%-14% below baseline levels for both NSW and VIC, and residential presence increased by 5%-6% over pre-COVID baseline outside of lockdown conditions. These results all suggest that a new COVID-normal of greater working from home, less public transport utilisation and marginally suppressed customer-facing retail has emerged in non-lockdown scenarios.
Figure 2 (Tableau) presents mobility data grouped by outbreak in order to directly compare the response for NSW and Victorian outbreaks:
A major point of difference between VIC and NSW lockdowns was restrictions related to retail stores. During Stage 4 and circuit-breaker lockdowns VIC adopted a policy of closing all non-essential retail, with a specific, prescribed list of businesses that were permitted to open. NSW on the other hand preferred an initial approach of allowing retail to remain open, and a less prescribed approach in defining “essential” retail. Figure 3 (Tableau) specifically highlights Retail and Recreation mobility between these outbreaks:
The Victorian Stage 3 restrictions achieved a suppression of Retail mobility by 35% to 40%. The initial lockdown restrictions in NSW during 2021 initial achieved a 35% suppression in Retail mobility, before spontaneously reducing to 45% below baseline. The Victorian circuit-breaker lockdowns in 2021 also achieved a 45% average reduction in Retail mobility.
The Stage 4 Victorian restrictions reduced Retail and Recreation further to 60% below baseline. Across Workplace, Transit and Residential settings, mobility for NSW is approaching levels seen during Stage 4 and circuit-breaker Victorian lockdowns. Crucially, however, it is approaching these reduced mobility levels at a much slower pace compared to the 2021 VIC circuit-breaker lockdowns. Thus the burden of active cases in the community is much higher, and it would be expected that reaching zero community transmission will take longer. There also appears to still be room for NSW to further restrict Retail and Recreation mobility to reach levels encountered during Victoria’s Stage 4 lockdown, which included a 5km movement radius and nighttime curfews.
