Modelling the Potential Public Health Impact of Different COVID-19 Vaccination Strategies with an Adapted Vaccine in Singapore

Figures & data

Figure 1. Model structure combining (a) Markov cohort model and (b) decision tree component.

In the Markov model component, individuals transition weekly through health states related to COVID-19 protection and infection. If individuals transition into any infection state, they immediately enter (B) the decision tree component for sorting. Green circles indicate decision points, with probabilities informed by the level of protection against COVID-19 in the particular infected state from which an individual arrives. Red triangles indicate decision tree end points, from which participants reenter the Markov model component.

Table 1. Outcomes of vaccination in various age and risk groups.

	Base Case: Age ≥65 Years and High Risk*			Age >50 Years and High Risk**			Age >50 Years, Age 5–11 Years, and High Risk***
	No Vaccination	Vaccination	Incremental Impact	No Vaccination	Vaccination	Incremental Impact	No Vaccination	Vaccination	Incremental Impact
Vaccine doses administered (million)	0	1.36	1.36	0	1.61	1.61	0	1.67	1.67
Deaths	879	641	239	879	631	248	879	631	248
Hospitalizations	107,341	85,783	21,558	107,341	84,273	23,067	107,535	84,401	23,134
Infections (millions)	3.50	3.22	0.28	3.50	3.17	0.33	3.50	3.16	0.34
Direct medical costs (million SGD)	2,877	2,600	277	2,877	2,565	312	2,951	2,630	321
Testing cost (million SGD)	787	737	50	787	728	59	813	751	62
AE management cost (thousand SGD)	0	168	−168	0	199	−199	0	0	0
Inpatient treatment cost (million SGD)	642	510	132	642	501	141	643	501	142
Outpatient treatment cost (million SGD)	226	209	17	226	205	20	232	211	21
Post-COVID condition treatment cost (million SGD)	1,223	1,144	79	1,223	1,130	92	1,263	1,166	97
Indirect costs (million SGD)	11,975	11,292	684	11,975	11,156	819	11,975	11,153	823
Productivity loss due to illness (million SGD)	11,967	11,284	683	11,967	11,148	819	11,967	11,145	822
Productivity loss due to death (million SGD)	0.1	0.1	0.0	0.1	0.1	0.0	0.1	0.1	0.0
Education loss (million SGD)	8.1	7.9	0.2	8.1	7.9	0.2	8.4	8.0	0.4

*Base case coverage: standard-risk population: 0% (6mo-64 years), 88% (65–74 years), and 85% (≥75 years); high-risk population: 29% (5–11 years), 79% (12–17 years), 85% (18–29 years), 89% (30–49 years), 90% (50–64 years), 88% (65–74 years), and 85% (≥75 years).

**Base case coverage: standard-risk population: 0% (6mo-49 years), 90% (50–64 years), 88% (65–74 years), and 85% (≥75 years); high-risk population: 29% (5–11 years), 79% (12–17 years), 85% (18–29 years), 89% (30–49 years), 90% (50–64 years), 88% (65–74 years), and 85% (≥75 years).

***Base case coverage: standard-risk population: 29% (5–11 years), 90% (50–64 years), 88% (65–74 years), and 85% (≥75 years); high-risk population: 29% (5–11 years), 79% (12–17 years), 85% (18–29 years), 89% (30–49 years), 90% (50–64 years), 88% (65–74 years), and 85% (≥75 years).

Table 5. Scenario analysis results varying the disease burden in analysis of the full Singapore population.

	Delta Variant (July 2021-September 2021)	Omicron Variant (January 2022-March 2022)*
Vaccine doses administered	3,241,970 (0%)	3,241,970
Deaths averted	10 (−96%)	248
Hospitalizations averted	1,673 (−94%)	28,639
Infections averted	29,912 (−96%)	721,807
Direct medical costs averted (million SGD)	26 (−95%)	552
Indirect costs averted (million SGD)	100 (−96%)	2,230

*base case.

Table 2. Base case results and expanding vaccination in the standard-risk population.

	Base case: Age ≥ 65 and High Risk*	Standard Risk Coverage: 25%	Standard Risk Coverage: 50%	Standard Risk Coverage: 75%
Vaccine doses administered	1,359,269	1,935,740 (42%)	2,512,212 (85%)	3,088,684 (127%)
Deaths averted	239	241 (1%)	244 (2%)	246 (3%)
Hospitalizations averted	21,558	23,616 (10%)	25,674 (19%)	27,732 (29%)
Infections averted	278,614	413,513 (48%)	548,411 (97%)	683,309 (145%)
Direct medical costs averted (million SGD)	277	361 (30%)	444 (60%)	527 (90%)
Indirect costs averted (million SGD)	684	1,120 (64%)	1,557 (128%)	1,994 (192%)

* Base case coverage: standard-risk population: 0% (6 months-65 years), 88% (65–74 years), and 85% (≥75 years); high-risk population: 0% (6 months-4 years), 29% (5–11 years), 79% (12–17 years), 85% (18–29 years), 89% (12–49 years), 90% (50–64 years) 88% (65–74 years), and 85% (≥75 years).

Standard-risk population comprises individuals aged <65 years with no comorbidities.

Table 3. Alternative base case results and expanding vaccination in the standard-risk population.

	Base case: Age > 50 and High Risk*	Standard Risk Coverage: 25%	Standard Risk Coverage: 50%	Standard Risk Coverage: 75%
Vaccine doses administered	1,605,692	2,113,974 (32%)	2,622,256 (63%)	3,130,538 (95%)
Deaths averted	248	248 (0%)	248 (0%)	248 (0%)
Hospitalizations averted	23,067	24,708 (7%)	26,348 (14%)	27,989 (21%)
Infections averted	327,314	448,737 (37%)	570,159 (74%)	691,581 (111%)
Direct medical costs averted (million SGD)	312	386 (24%)	459 (47%)	533 (71%)
Indirect costs averted (million SGD)	819	1,218 (49%)	1,618 (97%)	2,017 (146%)

*Base case coverage: standard-risk population: 0% (6 months-4 years), 0% (5–49 years), 90% (50–64 years) 88% (65–74 years), and 85% (≥75 years); high-risk population: 0% (6 months-4 years), 29% (5–11 years), 79% (12–17 years), 85% (18–29 years), 89% (12–49 years), 90% (50–64 years) 88% (65–74 years), and 85% (≥75 years).

Standard-risk population comprises individuals aged 5–49 years with no comorbidities.

Table 4. Alternative base case results and expanding vaccination in the standard-risk population.

	Base case: Age 5 mo-11 years or >50 years and High Risk*	Standard Risk Coverage: 25%	Standard Risk Coverage: 50%	Standard Risk Coverage: 75%
Vaccine doses administered	1,676,751	2,129,078 (33%)	2,581,405 (61%)	3,033,731 (89%)
Deaths averted	248	248 (0%)	248 (0%)	248 (0%)
Hospitalizations averted	23,134	24,750 (7%)	26,365 (14%)	27,981 (21%)
Infections averted	342,280	451,849 (38%)	561,417 (72%)	670,986 (105%)
Direct medical costs averted (million SGD)	321	388 (24%)	455 (46%)	522 (67%)
Indirect costs averted (million SGD)	823	1,222 (49%)	1,621 (98%)	2,020 (147%)

*Base case coverage: standard-risk population: 0% (6 months-4 years), 29% (5–11 years), 0% (12–49 years), 90% (50–64 years) 88% (65–74 years), and 85% (≥75 years); high-risk population: 0% (6 months-4 years), 29% (5–11 years), 79% (12–17 years), 85% (18–29 years), 89% (12–49 years), 90% (50–64 years) 88% (65–74 years), and 85% (≥75 years).

Standard-risk population comprises individuals aged 12–49 years with no comorbidities.

Figure 2. Tornado diagram showing the 10 most impact parameters identified in the deterministic sensitivity analysis varying parameters by ± 20% on the total incremental cost savings in the high-risk population and individuals aged ≥ 50. Color of the bar indicates whether the parameter is at its lower or upper bound.