The effect of public health interventions on COVID-19 incidence in Queensland, Australia: a spatial cluster analysis

Figures & data

Figure 1. Timeline of changes in vaccination coverage, border changes and masking requirements with the number of daily COVID-19 case notifications (orange) with seven day moving average and number of SA2s with recorded cases (blue).

Table 1. Phase details of Queensland government state and international border closures and restrictions based on population vaccination targets of 70%, 80% and 90% and recommended masking requirements.

International and state border closures	Phase 1 (pre-opening) (≥70% vaccination)	Phase 2 (≥80% vaccination level)	Phase 3 (≥90% vaccination level)
Time period	1 January 2021 to 13 December 2021 (346 days)	13 December 2021 to 15 January 2022 (34 days)	15 January 2022 to 19 July 2022 (185 days)
Domestic travellers	State borders periodically close for NSW and Vic outbreaks No restrictions for domestic travellers if not from a hot spot Quarantine required from hot spots − 14 days	Open state borders (air or road) From 15th January Fully vaccinated travellers with a negative test No quarantine required.	No restrictions for domestic travellers Restricted entry to high-risk facilities for unvaccinated individuals
International travellers	Limited entry for international travellers – mandatory 14-day hotel quarantine	Increased numbers of international travellers − 14-day home quarantine.	International travellers no longer required to quarantine. Negative test required within 24 h of arrival
Mask requirements	Level 1	Level 2	Level 3
Time period	13 December 2021 to 1 January 2022 (20 days)	2 January 2022 to 4 March 2022 (62 days)	5 March 2022 to 19th July 2022 (137 days)
Details	Masks required in: Supermarkets and shops Public transport and rideshare. Airports and planes Cinemas and theatre	Masks required in: Workplaces Pubs, clubs and cafes (except seated) Indoor stadiums and sports arenas Libraries Hairdressers and nail salons Medical centre waiting rooms	Mandatory masks in high-risk settings only: Healthcare, aged care, disability accommodation, prisons or detention centres Public transport and rideshare. Airports and planes
		Includes: Level 1 restrictions	Or if experiencing symptoms, awaiting test results, close contacts or diagnosed with COVID-19

Source: Queensland Government.

Figure 2. Scatter plots with regression line for daily COVID-19 cases (green) and SA2 regions (blue) by phase of border opening (A, B) and masking levels (C–E) from 13 December 2021 to 19 July 2022.

Figure 3. Percentage of the population having received two doses of COVID-19 vaccine by SA3 region at vaccination target thresholds. Left to right: 70% state population coverage (15 November 2021), 80% state population coverage (13 December 2021) and 90% state population coverage (17 January 2022).

Figure 4. COVID-19 incidence per 100,000 population per 100 days by border closure phases for Queensland (A: phase one, B: phase 2 and C: phase 3; D–F: SEQ detail).

Figure 5. COVID-19 incidence per 100,000 population per 100 days by masking requirements for Queensland (A: level 1, B: level 2 and C: level 3; D–F: SEQ detail).

Figure 6. Relative risk by SA2 with MLC by border restrictions in Queensland with details for SEQ (A: phase one, B: phase 2 and C: phase 3) showing clusters by area (cluster outline) and proportional to population (blue gradient and diameter).

Table 2. Details of most-likely clusters (MLC) of COVID-19 infection by intervention phase.

Intervention phase	Most-likely cluster number	No. of SA2 regions	Region	Population at risk	Radius (km)	Observed cases (no.)	Expected cases (no.)	Likelihood ratio	RR	p Value (sig. ≤0.05)
Border phase 1 and >70% vaccination	1	8	SEQ	78,263	3.21	99	4.65	224.85	30.83	<.00001
	2	9	SEQ	76,870	2.56	19	4.56	13.01	4.37	.0010
	3	2	SEQ	20,414	1.88	10	1.21	12.44	8.49	.0017
	4	1	Southwest QLD	6667	N/A	6	0.4	10.75	15.44	.0074
Border phase 2 and >80% vaccination	1	40	SEQ	506,847	24.46	24,315	15,198	2609.64	1.71	<.00001
	2	41	SEQ	369,478	6.91	18,034	11,079	2000.14	1.71	<.00001
	3	20	FNQ	166,080	28.28	9561	4980	1725.14	1.98	<.00001
	4	40	SEQ	477,276	14.12	20,373	14,311	11264.13	1.49	<.00001
	5	1	North Queensland	14,644	N/A	907	439	190.74	2.07	<.00001
	6	2	SEQ	12,085	2.45	683	362	112.6	1.89	<.00001
	7	7	SEQ	86,476	6.77	3112	2593	49.65	1.20	<.00001
Border phase 3 and >90% vaccination	1	40	FNQ	279,951	838.75	51,554	21,247	16650.43	2.64	<.00001
	2	50	North Queensland	380,274	256.72	32,575	28,861	248.18	1.14	<.00001
	3	1	SEQ	6,413	N/A	974	487	188.71	2.00	<.00001
	4	8	SEQ	135,942	9.58	12,170	10,317	161.65	1.19	<.00001
	5	14	SEQ	173,018	12.39	15,050	13,131	138.64	1.15	<.00001
	6	6	Fraser Coast	62,096	13.04	5886	4713	136.99	1.25	<.00001
	7	9	SEQ	92,611	3.85	8384	7029	125.36	1.20	<.00001
	8	8	SEQ	172,996	13.00	14,701	13,130	93.73	1.12	<.00001
	9	12	SEQ	146,925	6.37	12,523	11,151	83.61	1.13	<.00001
	10	6	SEQ	76,207	5.73	6770	5784	80.93	1.17	<.00001
	11	6	SEQ	58,263	3.52	4923	4422	27.70	1.11	<.00001
	12	2	SEQ	22,798	2.44	2045	1730	27.18	1.18	<.00001
	13	1	Central QLD	7618	N/A	749	578	23.10	1.30	<.00001
	14	4	SEQ	43,913	3.46	3683	3333	17.94	1.11	<.00001
	15	14	SEQ	141,852	7.90	11,337	10,766	15.31	1.05	<.00001
	16	1	SEQ	8024	N/A	730	609	11.32	1.20	.0045
	17	1	SEQ	18,728	N/A	1595	1421	10.24	1.12	.0012
Mask level 1	1	20	SEQ	257,941	9.13	2366	996	727.93	2.56	<.00001
	2	38	SEQ	344,372	6.37	2781	1329	658.78	2.27	<.00001
	3	41	SEQ	477,276	14.12	3355	1842	562.87	1.99	<.00001
	4	2	SEQ	12,085	2.45	186	47	118.41	4.02	<.00001
	5	1	South West QLD	7543	N/A	145	29	117.25	5.01	<.00001
	6	1	North QLD	14,644	N/A	189	56	96.11	3.37	<.00001
	7	1	FNQ	11,975	N/A	91	46	16.92	1.97	.000035
	8	1	South Burnett	9833	N/A	79	38	16.91	2.09	.000035
	9	1	FNQ	5663	N/A	51	22	14.09	2.34	.00044
	10	1	South West	15,425	N/A	102	59	12.50	1.72	.0018
Mask level 2	1	33	FNQ	232,783	791.76	30,344	14,427	7060.27	2.22	<.00001
	2	40	SEQ	506,847	24.46	41,060	81,526	2570.50	1.32	<.00001
	3	22	SEQ	261,025	13.54	20,943	16,178	678.7	1.31	<.00001
	4	23	SEQ	247,564	11.83	18,672	15,343	355.5	1.23	<.00001
	5	53	SEQ	482,759	9.12	33,743	29,920	259.42	1.14	<.00001
	6	7	SEQ	86,476	6.77	6705	5359	159.14	1.26	<.00001
	7	9	SEQ	102,024	5.38	7115	6323	48.62	1.13	<.00001
	8	1	North QLD	14,644	N/A	1076	908	14.78	1.19	.00018
	9	1	North QLD	5315	N/A	414	329	10.05	1.26	.013
	10	2	SEQ	12,085	2.45	867	749	8.86	1.16	.042
End masking requirements	1	42	FNQ	281,511	488.26	29,510	11,273	11029.21	2.88	<.00001
	2	10	Fraser Coast	100,488	27.30	6606	4024	708.98	1.66	<.00001
	3	9	SEQ	92,611	3.85	4930	3708	185.77	1.34	<.00001
	4	50	North QLD	380,274	256.72	17,491	15,228	173.7	1.16	<.00001
	5	19	SEQ	204,257	5.84	9705	8179	140.01	1.20	<.00001
	6	8	SEQ	135,942	9.58	6349	5444	88.34	1.19	<.00001
	7	6	SEQ	76,207	5.73	3576	3052	43.34	1.17	<.00001
	8	1	SEQ	11,645	N/A	630	466	25.92	1.35	<.00001
	9	1	SEQ	10,833	N/A	569	434	25.92	1.31	<.00001
	10	2	SEQ	12,528	1.17	633	502	15.9	1.26	.000088
	11	2	SEQ	16,570	2.21	805	664	14.16	1.21	.00042
	12	5	South West	57,409	12.59	2543	2299	12.67	1.11	.0016
	13	1	South West	6957	N/A	364	279	11.95	1.31	.0030
	14	1	SEQ	19,418	N/A	916	778	11.7	1.18	.0038
	15	1	SEQ	18,728	N/A	873	750	9.62	1.16	.026

Figure 7. Relative risk by SA2 with MLC by masking levels in Queensland with details for SEQ (A: phase one, B: phase 2 and C: phase 3) showing clusters by area (cluster outline) and proportional to population (blue gradient and diameter).

Figure 8. Map showing cluster and outlier analysis by intervention phases, border (A–C) masking (D–F), showing unusual outliers as high-low or low-high and clusters as high-high or low-low.

Data availability statement

The data that support the findings of this study are from publicly available sources. COVID-19 incidence data for Queensland, Australia are available from the COVID-19 Resources Open Data Portal from the Queensland Government repository (CC BY 4.0) (https://www.data.qld.gov.au/dataset/queensland-covid-19-case-line-list-location-source-of-infection/resource/1dbae506-d73c-4c19-b727-e8654b8be95a) [54]. All Australian SA2 population estimates data for 2021–2022 are available for download from the Australian Bureau of Statistics (ABS) data repository (CC BY 4.0) (https://www.abs.gov.au/statistics/people/population/regional-population/2021-22/32180DS0001_2021-22r.xlsx) [55].