Challenges in the prophylaxis of severe respiratory syncytial virus infections

Feitosa, Dana C.; Vieira, Sandra E.

doi:10.1016/j.jped.2025.04.003

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Original articles • J. Pediatr. (Rio J.) 101 (5) • 2025 • https://doi.org/10.1016/j.jped.2025.04.003 linkcopy

Challenges in the prophylaxis of severe respiratory syncytial virus infections

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objective To analyze palivizumab prophylaxis adherence among newborns and infants, as well as identify its challenges and facilitators.

Methods This retrospective study reviewed medical records of individuals who received palivizumab between 2008 and 2019 at a referral center in a metropolitan city in Brazil. Three adherence criteria were evaluated: an adequate number of doses received, interval between doses ≤ 35 days, and complete adherence (meeting both prior criteria). Associations between these criteria and sociodemographic/clinical variables, as well as post-prophylaxis bronchiolitis-related hospitalizations, were examined.

Results A total of 908 participants (mean age 6.7 months,50.8 % male,57.8 % residing in the city) were analyzed. During the three-season study period, a total of 1,158 doses were prescribed, and complete adherence was observed in 44.5 % of cases. Based on both the adequate number of doses and complete adherence criteria, lower adherence was noted among those living outside the city (52.8 % vs.60.9 %, p = 0.01; and 41.5 %vs.48.5 %, p = 0.03, respectively) and infants born to mothers younger than 20 years (39.7 % vs.60.3 %,p < 0.01; and 31.5 %vs.68.5 %, p = 0.02, respectively). Infants with gestational age < 28 weeks (65.8 % vs.34.2 %, p = 0.03) and birth weight < 1000 g (67.8 % vs.32.2 %, p = 0.03) had higher adherence under the adequate number of doses criterion. No association emerged between adherence and bronchiolitis-related hospitalizations, which were predominantly linked to maternal smoking during pregnancy and chronic lung disease.

Conclusion Adherence to palivizumab prophylaxis was low, highlighting the need to address geographic barriers and maternal age factors. Extreme prematurity and very low birth weight facilitated adherence, indicating that more targeted strategies or decentralized administration may improve outcomes in high-risk populations.

Keywords
Respiratory syncytial virus infections; Palivizumab; Medication adherence; Immunization, Passive; Infant, Premature

Characteristics of infants	n (%)
Sex
Female	432 (47.6)
Male	462 (50.9)
Ethnicity
White	479 (52.8)
Black	30 (3.3)
Asian	2 (0.2)
Mixed-race	149 (16.4)
Age (months)
Mean age at first Palivizumab dose	6.7 (±5.3)
Weight (grams)
Mean weight at first Palivizumab dose	5355 (±2.5)
Place of residence
City of São Paulo	525 (57.8)
Other cities	368 (40.5)
Maternal age (years)
<20	65 (7.2)
21-30	245 (27.0)
>30	277 (30.5)
Maternal smoking during pregnancy
Smokers	48 (5.3)
Non-smokers	329 (36.2)
Indications for Palivizumab
GAa <29 weeks without chronic lung disease	100 (11.0)
Chronic lung disease of prematurity (CLD)	326 (35.9)
Congenital heart disease (CHD)	458 (50.4)
First palivizumab dose
Administered in the maternity ward	179 (19.7)
On oxygen therapyb	101 (14.0)
Deaths during the study period
CHD	14 (1.5)
CLD	5 (0.6)
Total deaths	19 (2.1)

	Adherence criterion
	Number of dosesa			Interval between dosesb			Full adherencec
Characteristics	Inadequate	Adequate	p e	Inadequate	Adequate	p e	No	Yes	p e
Sex
Female	176 (45.7 %)	260 (49.7 %)	0,23	98 (49.2 %)	280 (47.5 %)	0,66	227 (46.0 %)	209 (50.5 %)	0.17
Male	209 (54.3 %)	263 (50.3 %)	0,23	101 (50.8 %)	310 (52.5 %)	0,66	267 (54.0 %)	205 (49.5 %)	0.17
Ethnicity
White	209 (74.4 %)	273 (71.5 %)	0.44	106 (70.7 %)	315 (73.4 %)	0.67	263 (72.3 %)	219 (73.2 %)	0.16
Black	10 (3.6 %)	20 (5.2 %)	0.29	6 (4.0 %)	19 (4.4 %)	0.82	13 (3.6 %)	17 (5.7 %)	0.19
Asian	0 (0.0 %)	2 (0.5 %)	0.22	0 (0.0 %)	2 (0.5 %)	0.40	0 (0.0 %)	2 (0.7 %)	0.12
Mixed-race	62 (22.1 %)	87 (22.8 %)	0.92	38 (25.3 %)	93 (21.7 %)	0.36	88 (24.2 %)	61 (20.4 %)	0.25
Maternal smoking during pregnancy
Yes	20 (14.5 %)	28 (11.7 %)	0,43	7 (7.6 %)	34 (14.0 %)	0,10	23 (12.0 %)	25 (13.4 %)	0.68
No	118 (85.5 %)	211 (88.3 %)	0,43	85 (92.4 %)	208 (86.0 %)	0,10	168 (88.0 %)	161 (86.6 %)	0.68
Maternal age (years)
<20	44 (14,6 %)	29 (6,5 %)	<0.01	15 (8,7 %)	42 (8,6 %)	0,90	50 (12,6 %)	23 (6,6 %)	0,02
21-30	123 (40,9 %)	188 (42,4 %)	0.06	73 (42,2 %)	197 (40,4 %)	0.67	164 (41,2 %)	148 (42,7 %)	0.69
>30	134 (44,5 %)	226 (51,0 %)	0.08	85 (49,1 %)	249 (51,0 %)	0.67	184 (46,2 %)	176 (50,7 %)	0.22
Prophylaxis indicationd
AG <29 weeks	31 (31.0 %)	69 (69.0 %)	0.02	27 (29.7 %)	64 (70.3 %)	0.58	50 (50.0 %)	50 (50.0 %)	0.42
DPC	131 (40.2 %)	195 (59.8 %)		66 (23.2 %)	218 (76.8 %)		170 (52.1 %)	156 (47.9 %)
CC	210 (45.9 %)	248 (54.1 %)		105 (26.3 %)	295 (73.8 %)		261 (57.0 %)	197 (43.0 %)
Birth weight
<1,000 g	65 (19.9 %)	137 (28.7 %)	0.03	47 (26.4 %)	135 (25.6 %)	0.67	95 (22.2 %)	107 (28.5 %)	0,14
1,000−1,499 g	71 (21.8 %)	103 (21.6 %)	0.95	34 (19.1 %)	119 (22.5 %)	0.33	92 (21.5 %)	82 (21.9 %)	0.90
1,500-2,499 g	66 (20.2 %)	76 (15.9 %)	0.11	35 (19.7 %)	87 (16.5 %)	0.34	84 (19.6 %)	58 (15.5 %)	0.12
≥2,500 g	124 (38.0 %)	161 (33.8 %)	0.21	62 (34.8 %)	187 (35.4 %)	0.89	157 (36.7 %)	128 (34.1 %)	0.45
Gestational age (weeks)
<29	55 (16.2 %)	106 (21.6 %)	0,03	39 (21.2 %)	108 (19.9 %)	0,52	80 (18.1 %)	81 (20.9 %)	0,26
29-31	83 (24.4 %)	136 (27.8 %)	0,28	45 (24.5 %)	147 (27.1 %)	0,47	110 (24.8 %)	109 (28.2 %)	0,27
32-33	16 (4.7)	30 (6.1 %)	0,38	10 (5.4 %)	33 (6.1 %)	0,74	24 (5.4 %)	22 (5.7 %)	0,87
34-36	47 (13.8 %)	49 (10.0 %)	0,09	27 (14.7 %)	52 (9.6 %)	0,06	60 (13.5 %)	36 (9.3 %)	0,06
37-41	135 (39.7 %)	168 (34.3 %)	0,11	62 (33.7 %)	198 (36.5 %)	0,49	165 (37.2 %)	138 (35.7 %)	0,63
≥42	4 (1.2 %)	1 (0.2 %)	0.16	1 (0.5 %)	4 (0.7 %)	1,00	4 (0.9 %)	1 (0.3 %)	0,37
Place of residence
City of São Paulo	208 (39.1 %)	324 (60.9 %)	<0.01	112 (23.9 %)	356 (77.7 %)	0.30	274 (51.5 %)	258 (48.5 %)	0.03
Other cities	177 (47.2 %)	198 (52.8 %)	<0.01	87 (27.2 %)	233 (72.8 %)	0.30	220 (58.6 %)	155 (41.3 %)	0.03

Admission diagnosis	Number of doses			Intervals between doses			Full adherence
	Inadequate N (%)	Adequate N (%)	p-value	Inadequate N (%)	Adequate N (%)	p	No N (%)	Yes N (%)	p-value
Bronchiolitis N = 174	90 (41.7)	84 (35.1)	0.15	34 (30.9)	117 (41.1)	0.06	106 (39.4)	68 (36.6)	0.53
Any diagnosis N = 473	228 (74.8)	245 (57.6)	<0.01	114 (66.7)	297 (63.1)	0,40	282 (70.5)	191(57.9)	<0.01

	Diagnosis
Characteristics of hospitalized infants	Bronchiolitis N = 174	Other diagnosis N = 274	p-value
Birth weight (grams)
<1,000	46 (27.7 %)	44 (16.7 %)	<0.01
1,000-1,499	38 (22.9 %)	39 (14.8 %)	0.03
1,500-2,499	27 (16.3 %)	47 (17.9 %)	0.07
2,500	55 (33.1 %)	133 (50.6 %)	<0.01
Gestational age (weeks)
<28	42 (24.9 %)	35 (13.1 %)	<0.01
28-31	44 (26.0 %)	43 (16.1 %)	0.01
32-33	7 (4.1 %)	14 (5.2 %)	0.60
34-36	18 (10.7 %)	43 (16.1 %)	0.11
37-41	58 (34.3 %)	129 (48.3 %)	<0.01
≥42	0 (0.0 %)	3 (1.1 %)	0.28
Prophylaxis indicationa
GA <29 weeks without CLD	19 (10.9 %)	22 (7.9 %)	0.30
CLD	75 (43.1 %)	66 (23.6 %)	<0.01
CHD	80 (46.0 %)	186 (66.4 %)	<0.01
Therapies in use at the time of Palivizumab administration
Bronchodilator	27 (16.5 %)	18 (7.3 %)	<0.01
Inhaled corticosteroid	54 (32.9 %)	40 (16.1 %)	<0.01
Oxygen therapy	30 (18.2 %)	27 (9.9 %)	0,01
Sex
Female	79 (45.4 %)	127 (45.2 %)	0.97
Male	95 (54.6 %)	154 (54.8 %)	0.97
Place of residence
City of São Paulo	97 (55.7 %)	172 (61.2 %)	0.25
Other cities	77 (44.3 %)	109 (38.8 %)	0.25
Maternal smoking during pregnancy	15 (17.4 %)	8 (8.1 %)	0.05

Model (according to adherence criterion)	ORa	IC 95 %b		p-value
Model 1 - adequate number of dosese
Adequate number of doses	0,79	0,46	1,36	0,40
IGc ≤9 weeks	1,81	0,79	4,11	0,16
CLDd	4,42	2,28	8,59	0,00
Congenital heart disease	1,01	0,80	1,25	1,00
Maternal smoking during pregnancy	0,52	0,22	1,20	0,13
Use of oxygen after discharge	0,91	0,44	1,88	0,80
Residence in São Paulo	0,99	0,56	1,75	0,97
Model 2 - adequate interval between dosesf
Adequate intervals between doses	1,58	0,84	2,96	0,16
IGc ≤29 weeks	2,08	0,85	5,08	0,11
CLDd	4,09	1,97	8,48	0,00
Congenital heart disease	1,01	0,73	1,43	1,00
Maternal smoking during pregnancy	0,41	0,17	1,02	0,06
Use of oxygen after discharge	0,82	0,37	1,79	0,61
Residence in São Paulo	0,95	0,51	1,76	0,87
Model 3 - full adherence g
Full Adherence	0,94	0,55	1,61	0,83
IGc ≤29 weeks	1,81	0,79	4,11	0,16
CLDd	4,49	2,31	8,74	0,00
Congenital heart disease	1,01	0,73	1,43	1,00
Maternal smoking during pregnancy	0,50	0,22	1,18	0,11
Use of oxygen after discharge	0,92	0,45	1,90	0,83
Residence in São Paulo	1,00	0,56	1,76	0,99

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[TFN1] ^a
GA, gestational age.

[TFN2] ^b
Received home oxygen therapy at the time of the first dose.