Cost utility of palivizumab prophylaxis among pre-term infants in the United States: a national policy perspective

Figures & data

Figure 1.  Structure of decision tree model. ICU, intensive care unit; RSV, respiratory syncytial virus.

Table 1.  Blended inputs from Medicaid and commercial populations for base case.*

Variable	Infant population	Medicaid	Source	Commercial	Source	Blended value (60% Medicaid, 40% commercial)
Background risk of RSV hospitalization	<32 wGA, ≤6 mo CA	18.5%	†	10.7%	†	15.4%
	32–34 wGA, ≤3 mo CA with 2009 AAP RF	13.4%	†	7.1%	†	10.9%
	32–35 wGA, ≤6 mo CA with 2006 AAP RF
	32–35 wGA, ≤6 mo CA with ≤1 RF	3.4%	†	1.7%	†	2.7%
Direct medical costs ∼1 year after RSV infection compared with placebo	<32 wGA, ≤6 mo CA	$39,399	Shi et al.7	$32,458	Stewart et al.8	$36,622
	32–34 wGA, ≤3 mo CA with 2009 AAP RF	$20,160	Shi et al.7	$25,368	Stewart et al.8	$22,243
	32–35 wGA, ≤6 mo CA with 2006 AAP RF
Cost of palivizumab	All groups	100 mg, $1,190.97 50 mg, $631.10	Estimated average public cost for palivizumab; MedImmune, Data on File.	100 mg, $2027.80 50 mg, $1073.88	WAC; Thomson Healthcare, Inc. 201017	100 mg, $1,525.70 50 mg, $808.12

* All other inputs in the model remained the same as the original model in the Medicaid population (see Weiner et al.2).

† We first estimated the background RSV hospitalization rates for infants of <32 wGA, ≤6 months CA (10.7%); 32–34 wGA, ≤3 months CA, 2009 AAP RF (7.1%); 32–35 wGA, ≤6 months CA, 2006 AAP RF (7.1%); and 32–35 wGA, ≤6 months CA, ≤1 RF (1.7%) from Checchia et al.14 (10.7%) and Sampalis et al.20 (7.1% and 1.7%). To obtain rates of RSV hospitalization for these cohorts covered by Medicaid, we converted these probabilities to odds (O = P/[1 − P], where O = odds and P = probability). We then multiplied the baseline odds by the OR of 2.03 (95% CI = 1.99–2.06), the increased odds of RSV hospitalization among infants from the Medicaid California population compared with the non-Medicaid California population. Finally, we converted the transformed OR to probabilities of RSV hospitalization for Medicaid infants of < 32 wGA, ≤ 6 months CA (18.5%); 32–34 wGA, ≤ 3 months CA with 2009 AAP RF (13.43%); 32–35 wGA, ≤ 6 months CA with 2006 AAP RF (13.43%); and 32–35 wGA, ≤ 6 months CA, with ≤ 1 RF (3.4%).

AAP, American Academy of Pediatrics; CA, chronologic age; OR, odds ratio; RF, risk factor; RSV, respiratory syncytial virus; WAC, wholesale acquisition cost; wGA, weeks gestational age.

Table 2.  Net costs and QALYs between palivizumab prophylaxis and no prophylaxis among four groups of infants in a Medicaid and commercially-insured population.

	<32 wGA, ≤6 mo CA*			32–34 wGA, ≤3 mo CA*, with AAP 2009 RFs^a			32–35 wGA, ≤6 mo CA*, with AAP 2006 RFs^b			32–35 wGA, ≤6 mo CA*, with ≤1 RF^c
	Palivizumab	No Prophylaxis	Difference	Palivizumab	No Prophylaxis	Difference	Palivizumab	No Prophylaxis	Difference	Palivizumab	No Prophylaxis	Difference
Prophylaxis costs	$4108	$0	$4108	$4095	$0	$4095	$5613	$0	$5613	$5613	$0	$5613
RSV-related costs	$1445	$5803	−$4357	$462	$2599	−$2137	$462	$2599	−$2137	$115	$650	−$534
Total costs	$5553	$5803	−$249	$4557	$2599	$1958	$6075	$2599	$3476	$5728	$650	$5078
QALY	30.907	30.869	0.038	30.909	30.865	0.0437	30.909	30.865	0.0437	30.911	30.900	0.011
ICER	–	–	Dominant	–	–	$44,774	–	–	$79,477	–	–	$464,476

*CA at the start of the RSV season (November 1).

^aHaving siblings <5 years of age and/or attending day care.

^bHaving two of the following: environmental air pollutants, congenital abnormalities of the airways, severe neuromuscular disease, school-aged siblings, or day care attendance.

^cRisk factors described in Sampalis et al.20

AAP, American Academy of Pediatrics; CA, chronologic age; ICER, incremental cost-effectiveness ratio calculated as incremental costs/incremental QALYs; QALY, quality-adjusted life-year; RF, risk factor; RSV, respiratory syncytial virus; wGA, weeks gestational age.

Table 3.  One-way sensitivity analysis for infants of <32 wGA, ≤6 months CA.

	Baseline results: Input		Dominant ICER
	Minimum	Maximum	Input minimum	Input maximum
RRR of RSV hospitalization (75.1%)	27.2%	91.5%	$85,613	Dominant
Background risk of RSV hospitalization (15.4%)	9.4%	34.2%	$61,956	Dominant
Discount rate for outcomes (3%)	0%	5%	Dominant	Dominant
Cost of palivizumab per mg^a ($15.71)	$12.57^b	$18.85^b $20.88^c	Dominant	$13,081 $25,737
Increased direct medical costs 12 months after RSV infection compared with placebo ($36,623)	$29,298	$43,947	$15,635	Dominant
Probability of infant fatality in ICU (4.3%)	3.0%	8.11%	Dominant	Dominant
Background risk of ICU admission (19.5%)	17.8%	48.4%	Dominant	Dominant
RRR of ICU admission (63%)	0%	94.8%	Dominant	Dominant

^aDue to weight-based dosing of palivizumab, the model calculations are based on a cost per mg value that is derived from the average cost per mg for 100-mg and 50-mg vials of palivizumab, respectively.

^bDerived from ±20% of the average base case cost per mg for 100-mg and 50-mg vials of palivizumab.

^cWAC scenario.

ICER, incremental cost-effectiveness ratio; ICU, intensive care unit; RRR, relative risk reduction; RSV, respiratory syncytial virus; LRI, lower respiratory tract illness; wGA, weeks gestational age; CA, chronologic age.

Table 4.  One-way sensitivity analysis for infants of 32–34 wGA, ≤3 months CA, with 2009 AAP risk factors.

	Baseline results: Input		$44,774 ICER
	Minimum	Maximum	Input minimum	Input maximum
Background risk for RSV hospitalization (10.9%)	8%	34.2%	$78,481	Dominant
Cost of palivizumab per mg^a ($15.71)	$12.57^b	$18.85^b $20.88^c	$27,485	$62,063 $73,218
RRR of RSV hospitalization (82.2%)	45.4%	94.2%	$79,560	$35,769
Discount rate for outcomes (3%)	0%	5%	$18,257	$65,856
Increased direct medical costs 12 months after RSV infection compared with placebo ($22,243)	$17,795	$26,692	$53,874	$35,674
Background risk of ICU admission (21.9%)	17.8%	48.4%	$54,351	$20,874
Probability of ICU death (6.1%)	3%	8.11%	$85,749	$33,920
RRR ICU admission (63%)	0%	94.8%	$50,500	$42,345

^aDue to weight-based dosing of palivizumab, the model calculations are based on a cost per mg value that is derived from the average cost per mg for 100-mg and 50-mg vials of palivizumab, respectively.

^bDerived from ±20% of the average base case cost per mg for 100-mg and 50-mg vials of palivizumab.

^cWAC scenario.

ICER, incremental cost-effectiveness ratio; ICU, intensive care unit; LRI, lower respiratory tract infection; RRR, relative risk reduction; RSV, respiratory syncytial virus; wGA, weeks gestational age; CA, chronologic age.

Table 5.  One-way sensitivity analysis for infants of 32–35 wGA, ≤6 months CA, with 2006 AAP risk factors.

	Baseline results: Input		$79,477 ICER
	Minimum	Maximum	Input minimum	Input maximum
Background risk for RSV hospitalization (10.9%)	8%	34.2%	$125,677	Dominant
Cost of palivizumab per mg^a ($15.71)	$12.57^b	$18.85^b $20.88^c	$55,482	$103,471 $118,952
Probability of case fatality in ICU (6.1%)	3.0%	8.11%	$152,210	$60,211
Discount rate for outcomes (3%)	0%	5%	$32,407	$116,899
RRR of RSV hospitalization (82.2%)	45.4%	94.2%	$120,982	$68,732
Background risk of ICU admission (21.9%)	17.8%	48.4%	$96,476	$37,052
Increased direct medical costs 12 months after RSV infection compared with placebo ($22,243)	$17,795	$26,692	$88,576	$70,377
RRR of ICU admission (63%)	0%	94.8%	$89,640	$75,166

^aDue to weight-based dosing of palivizumab, the model calculations are based on a cost per mg value that is derived from the average cost per mg for 100-mg and 50-mg vials of palivizumab, respectively.

^bDerived from ±20% of the average base case cost per mg for 100-mg and 50-mg vials of palivizumab.

^cWAC scenario.

ICER, incremental cost-effectiveness ratio; ICU, intensive care unit; LRI, lower respiratory tract infection; RRR, relative risk reduction; RSV, respiratory syncytial virus; wGA, weeks gestational age; CA, chronologic age.

Table 6.  One-way sensitivity analysis for infants of 32–35 wGA, ≤6 months CA, ≤1 risk factor.

	Baseline results: Input		$464,476 ICER
	Minimum	Maximum	Input minimum	Input maximum
Background risk of RSV hospitalization (2.7%)	1.7%	6.6%	$772,476	$162,699
Case fatality in the ICU (6.1%)	3%	8.11%	$889,543	$351,884
Discount rate for outcomes (3%)	0%	5%	$189,394	$683,178
Cost of palivizumab per mg^a ($15.71)	$12.57^b	$18.85^b $20.88^c	$368,498	$560,454 $622,378
Background risk of ICU admission (21.9%)	17.8%	48.4%	$563,827	$216,540
RRR of RSV hospitalization (82%)	45.4%	94.2%	$580,530	$434,435
Increased direct medical costs 12 months after RSV infection compared with placebo ($22,243)	$17,795	$26,692	$473,576	$455,377
RRR of ICU admission (63%)	0%	94.8%	$523,874	$439,283

^aDue to weight-based dosing of palivizumab, the model calculations are based on a cost per mg value that is derived from the average cost per mg for 100-mg and 50-mg vials of palivizumab, respectively.

^bDerived from ±20% of the average base case cost per mg for 100-mg and 50-mg vials of palivizumab.

^cWAC scenario.

ICER, incremental cost-effectiveness ratio; ICU, intensive care unit; LRI, lower respiratory tract infection; RRR, relative risk reduction; RSV, respiratory syncytial virus; wGA, weeks gestational age; CA, chronologic age.

Table 7A.  Two-way sensitivity analysis examining RSV hospitalization rates by palivizumab costs for infants <32 wGA, ≤6 months CA.

Scenario #	Background risk of RSV hospitalization: 15.4% (base case)	Cost of palivizumab per mg: $15.71 (base case)	ICER: Dominant (base case)
1	9.4% (min)	$12.57 (min)	$29,862
2	9.4% (min)	$20.08 (max)	$106,608
3	9.4% (min)	$20.88 (WAC scenario)	$114,758
4	34.2% (max)	$12.57 (min)	Dominant
5	34.2% (max)	$20.08 (max)	Dominant
6	34.2% (max)	$20.88 (WAC scenario)	Dominant

CA, chronologic age; ICER, incremental cost-effectiveness ratio; RSV, respiratory syncytial virus; wGA, weeks gestational age; WAC, wholesale acquisition cost.

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