The potential public health impact of the respiratory syncytial virus prefusion F protein vaccine in people aged ≥60 years in Japan: results of a Markov model analysis

Figures & data

Figure 1. Schematic description of Markov model.

vaccine efficacy was calculated against RSV-ARI and RSV-LRTD separately (indicated by syringe). The number of RSV-URTD was defined by the difference of RSV-ARI and RSV-LRTD.

ARI = acute respiratory infection; LRTD = lower respiratory tract disease; URTD = upper respiratory tract disease; Reinf = reinfection; RSV = respiratory syncytial virus; VE = vaccine efficacy.

Table 1. Epidemiologic and vaccine efficacy model input parameters.

Parameter	Base case	Lower bound	Upper bound	Sources
Epidemiology
Population size
60–64 years	7,445,000	N/A	N/A	[22]
65–69 years	7,535,000	N/A	N/A
70–74 years	9,337,000	N/A	N/A
75–79 years	7,030,000	N/A	N/A
80–84 years	5,743,000	N/A	N/A
85–89 years	3,955,000	N/A	N/A
≥90 years	2,636,000	N/A	N/A
RSV incidence
Annual incidence of RSV	0.042	0.0231^†	0.0781^†	[6,10,11]
Proportion of RSV-LRTD	47.60%	41.88%	53.32%	[23]
RSV-LRTD mortality
60–64 years	0.0032	0.0017	0.0045	[24,25,30–32]
65–74 years	0.0082	0.0044	0.0120
≥75 years	0.0145	0.0103	0.0188
Seasonality factor
January	101%	NA	NA	[27,28]
February	100%	NA	NA
March	64%	NA	NA
April	46%	NA	NA
May	50%	NA	NA
June	39%	NA	NA
July	25%	NA	NA
August	35%	NA	NA
September	67%	NA	NA
October	143%	NA	NA
November	339%	NA	NA
December	190%	NA	NA
Vaccination parameters
Coverage	50%	25%^‡	75%^‡	[35]
Vaccination date	September	N/A	N/A	Assumption
Peak % efficacy against RSV-ARI	74.17%	56.39%	94.01%	[34]
Peak % efficacy against RSV-LRTD	88.02%	65.80%	99.20%	[34]
Monthly waning rate for RSV-ARI vaccine efficacy	2.26%	0.30%	4.32%	[34]
Monthly waning for RSV-LRTD vaccine efficacy	2.10%	0.14%	4.30%	[34]
Health care resource use
Number of outpatient visits per RSV-URTD
60–74 years	0.438	N/A	N/A	[36,37]
≥75 years	0.528	N/A	N/A
Number of outpatient visits per RSV-LRTD
60–74 years	0.954	N/A	N/A	[36,37]
≥75 years	0.695	N/A	N/A
Number of hospitalizations per RSV-URTD event
60–74 years	0.00113	0.00056^‡	0.00169^‡	[36,37]
≥75 years	0.00111	0.00056^‡	0.00167^‡
Number of hospitalizations per RSV-LRTD event
60–74 years	0.108	0.054^‡	0.163^‡	[36,37]
≥75 years	0.344	0.172^‡	0.516^‡

ARI: acute respiratory infection; LRTD: lower respiratory tract disease; N/A: Not applicable; RSV: respiratory syncytial virus; URTD: upper respiratory tract disease.

^†Lower and upper bounds were obtained by multiplying reported RSV incidence (2.4%) by under-ascertainment factor of 1.5 and 2.2, respectively.

^‡Upper and lower bounds were changed by ± 50% (assumptions).

Table 2. PHI of RSVPreF3 OA vaccine over 3 years (base case).

Parameter	No vaccination 3 years	RSVPreF3 OA 3 years	Difference RSVPreF3 OA vs No vaccination 3 years
Total population	43,681,000	43,681,000	0
Population covered by 1 dose	0	21,840,500	21,840,500
RSV-ARI	5,311,823	4,303,324	−1,008,499
RSV-URTD	2,783,250	2,452,502	−330,748
RSV-LRTD	2,528,573	1,850,822	−677,752
RSV-URTD-related OP visits	1,327,194	1,169,253	−157,942
RSV-URTD-related hospitalizations	3,120	2,749	−371
RSV-LRTD-related OP visits	2,130,180	1,559,739	−570,442
RSV-LRTD-related hospitalizations	531,045	388,228	−142,817
RSV-LRTD deaths	25,455	18,615	−6,840
Number needed to vaccinate to prevent
1 RSV infection	22
1 hospitalization	153
1 death	3,194

Base case: older adults aged ≥60 years and coverage equal 50% over a three-year time horizon.

ARI:acute respiratory infection; LRTD: lower respiratory tract disease; OP: outpatient; PHI: public health impact; RSV: respiratory syncytial virus; RSVPreF3 OA: respiratory syncytial virus prefusion F protein vaccine for older adults; URTD: upper respiratory tract disease.

Figure 2. Tornado diagram – DSA results.

Bars are ordered vertically according to the size of the variable’s impact on the outcome. The variable with the greatest impact is on top. The lower (upper) bound end of the bar indicates the impact of the variable when its value is equal to the lower (upper) value of its range.

ARI: acute respiratory infection; DSA: deterministic sensitivity analysis; LRTD: lower respiratory tract disease; RSV: respiratory syncytial virus; URTD: upper respiratory tract disease.

Table 3. Scenario analyses.

Population
Population eligible for vaccination	≥60 years (Base case)	≥65 years	≥70 years	≥75 years
Total population	43,681,000	36,236,000	28,701,000	19,364,000
RSV-ARI cases avoided	1,008,499	833,599	657,045	439,177
Hospitalizations avoided	143,188	130,340	117,376	101,391
RSV deaths avoided	6,840	6,468	5,487	4,278
Vaccination coverage
Vaccination coverage	25%	50% (Base case)	75%	100%
RSV-ARI cases avoided	504,250	1,008,499	1,512,749	2,016,999
Hospitalizations avoided	71,594	143,188	214,782	286,376
RSV deaths avoided	3,420	6,840	10,259	13,679
Vaccination timing
Time of vaccine administration	6 months before the base case (March)	3 months before the base case (June)	September (Base case)	3 months after the base case (December)
RSV-ARI cases avoided	807,326	895,265	1,008,499	835,746
Hospitalizations avoided	123,133	132,170	143,188	124,308
RSV deaths avoided	5,889	6,318	6,840	5,943

ARI:acute respiratory infection; RSV: respiratory syncytial virus.

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