Immunogenicity of Haemophilus influenzae type b polysaccharidetetanus protein conjugate vaccine in children with sickle hemoglobinopathy or malignancies, and after systemic Haemophilus influenzae type b infection Sheldon L. Kaplan, MD, Teresa D u c k e t t , RN, D o n a l d H. M a h o n e y , Jr., MD, Laura L. K e n n e d y , RN, MSN, C i n d y M. Dukes, PAC, Don M. Schaffer, MD, a n d E d w a r d O. Mason, Jr., Phb From the Department of Pediatrics, Baylor College of Medicine and Texas Children's HospitaJ, Houston, and the Pasteur Merieux Company, Connaught Laboratories Inc., Swiftwater, Pennsylvania To determine the immunogenicity of H a e m o p h i l u s influenzae type b polysaccharide-tetanus protein conjugate vaccine in specific populations at risk, we administered vaccine to children with sickle cell anemia (n = 19; mean age, 18.3 months, malignancies (n = 18; mean age, 43.1 months), or a recent history of systemic H. influenzae type b infection (n = 17; mean age, 11.9 months). After one dose of polyribosylribitol phosphate-tetanus toxoid conjugate vaccine the geometric mean titers for polyribosylribitol phosphate antibody were 4.8 ~g/ml (14/19 >t t~g/ml), 1.4 ~g/ml (9/t8 >t t~g/ml), and 5.6 ;~g/ml (t5/t7 >1 t~g/ml) in these three groups, respectively. Children with sickle cell anemia or a recent history of systemic 14. influenzae type b infection had polyribosylribitol phosphate antibody levels c o m p a r a b l e to those of normal children of similar a g e after one or two doses of polyribosylribitol phosphate-tetanus toxoid conjugate vaccine. We conclude that this vaccine is immunogenic in children with underlying conditions associated with an increased risk of 14. influenzae type b infection. (J PEDJATRt992;t20:367-70)
The three licensed Haemophilus influenzae type b polyribosylribitol phosphate-protein conjugate vaccines (PRPdiphtheria toxoid, PRP-outer-membrane protein complex of Neisseria meningitidis, oligosaccharide-CRM197) are more immunogenic than PRP alone in children with sickle Supported by Pasteur Merieux Serum and Vaccines, Connaught Laboratories Inc., Swiftwater, Pa. Submitted for publication Sept. 9, 1991; accepted Nov. 4, 1991. Reprint requests: Sheldon L. Kaplan, MD, Infectious Disease Service, Texas Children's Hospital, Clinical Care Center, Mail Code 3-2371, 662l Fannin, Houston, TX 77030. 9/22/34793
cell anemia l4 or malignancies,5-7 or after systemic H. influenzae type b infection,s-l~ Furthermore, children who have had systemic H. influenzae type b infection despite PRP vaccination generally have protective levels of antiPRP PRP-D PRP-T
Polyribosylribitolphosphate PRP-diphtheria toxoid conjugate vaccine PRP-tetanus toxoid conjugate vaccine
PRP antibody after a vaccination with H. influenzae type b PRP-protein conjugate vaccine, l 1, 12 A fourth, unlicensed H. influenzae type b conjugate vaccine consists of H. influenzae type b capsular polysaccha-
367
368
Kaplan et al.
The Journal of Pediatrics March 1992
T a b l e . Polyribosylribitol phosphate antibody titer after vaccination with polyribosylribitol phosphate-tetanus toxoid conjugate
Group
N
Mean a g e at first dose (too)
Normal (12-15 mo.) Systemic 14. influenzae type b infection* Malignancy Sickle cell anemia Normal (17-24 mo)
49 17 18 19 16
12.5 + 0.5 11.9 _+ 5.2 43.1 _+ 18.3 18.3 +_ 15.1 20.4 + 2.5
Geometric mean titer (pg/ml) Before
0.08 (2/49) 0.14 (3/17) 0.14 (2/18) 0.10 (1/19) 0.16 (1/15)
[4] [6]? [6] [3] [5]
After I dose
After 2 doses
3.1 (36/48) 5.6 (15/17) 1.4 (9/18) 4.8 (14/19) 6.9 (14/16)
12.0 (47/49) 12.6 (10/10) 0.4 (1/2) 14.2 (8/9) --
Proportionwith PRP antibodyconcentrations>~1~g/ml givenin parentheses.Numberwith PRP antibodyconcentrations>0. l 5 tLg/mlgivenin brackets. *SystemicH. influenzaetype b infectioninvolvedmeningitisin 16 and arthritis in 1. tFor normal 12- to 15-month-oldchildrenversusthose with previousH. influenzae type b infections,p = 0,008
ride linked to tetanus protein. This vaccine has proved highly immunogenic in young infants) 3' 14 In comparative trials in which different H. influenzae type b conjugate vaccines were evaluated within the same population and antibodies were determined by the same assay, PRP-T resulted in higher tevels of antibody to PRP than did other conjugate vaccines, ls17 Sarnaik et al) 8 immunized 25 children with sickle cell anemia between 2 and 5 years of age with PRP-T; 5 of 25 children before and all of 23 after a single dose of PRP-T had > 1.0 #g/ml of PRP antibody. In this study we evaluated the immunogenicity of PRP-T in children with sickle cell anemia or malignancies and after systemic H. influenzae type b infection. METHODS Vaccine. The H. influenzae type b PRP-T was provided by Pasteur Merieux Company (Connaught Laboratories Inc., Swiftwater, Pa.). Each dose contained 10 #g purified H. influenzae type b capsular polysaccharide and 20 #g purified tetanus protein derived from the detoxifled tetanus toxoid. Lyophilized conjugate vaccine was reconstituted with 0.4% saline solution and administered intramuscularly in the thigh. Five different lots of PRP-T were administered during the study. Subjects. Three patient groups were sought for enrollment in this study as follows: (1) children younger than 20 months of age after systemic 1t. influenzae type b infection who were hospitalized at Texas Children's Hospital (all had H. influenzae type b isolated from cultures of blood, cerebrospinal fluid, or both), (2) children with sickle cell anemia who were younger than 5 years of age and who were being followed in the pediatric hematology clinic at Baylor College of Medicine, and (3) children with malignancies who were receiving maintenance chemotherapy. Exclusions for enrollment in the study included (1) previous immunization with an H. influenzae type b vaccine, (2) history of severe reaction to diphtheria-pertussis-tetanus vaccine or diphtheria-tetanus toxoid, (3) receipt of immune globulin or whole blood within the previous 3 months, (4) platelet count
less than 50,000 cells/mm 3 in children with malignancies, and (5) major cardiac anomaly or epilepsy. Normal children in two different age groups (17 to 24 months and 12 to 15 months) who were followed in the private office of one of the investigators (D.M.S.) were enrolled in PRP-T studies being conducted concomitantIy with the PRP-T studies in the at-risk patient populations. Sera from 16 of 100 normal children, 17 to 24 months of age and immunized with a single dose of PRP-T, were available for analysis. Sera from 49 normal children, 12 to 15 months of age and immunized with two doses of PRP-T, also were available for analysis. The protocol was approved by the institutional review boards of Baylor College of Medicine and Texas Children's Hospital. Informed parental consent and consent of the patient's private physician were obtained before any child's enrollment in the study. Vaccine schedule. Children in the three patient groups who were younger than 18 months of age at initial immunization received two doses of PRP-T separated by 2 months. Children in the three patient groups who were l 8 months of age or older received one dose of PRP-T. Children with sickle cell anemia received three doses of PRP-T if immunized before 6 months of age. Serum was obtained before and after each dose and 1 to 2 months after the final dose. Children with a recent history of systemic H. influenzae type b infection were immunized at least 1 month after discharge and bad to have received at least two doses of diphtheria-pertussis-tetanus vaccine before PRP-T immunization. Antibody assay. Total serum PRP antibody concentrations for all sera were measured by a radioantigen binding assay performed by Connaught Laboratories. The reference serum for this assay is FDA Hib antibody (lot 1983). The lower limit of detection for the assay was 0.06 ~g/ml. Sera with nondeteetable levels of anti-PRP antibody were assigned a value of 0.06 ~zg/ml for analysis. Statistical analysis. Comparisons among groups were performed by means of analysis of variance and the Student
Volume 120 Number 3
Immunogenicity of Hib-tetanus vaccine in at-risk children
t test. The proportion of children with levels of antibody to PRP _>0.15 #g/ml or > 1 #g/ml was analyzed by the Fisher Exact Test. RESULTS The number of children in each category receiving PRP-T is shown in the Table. The mean ages of the normal children 17 to 24 months of age and the children with sickle cell anemia were not significantly different. Similarly, the mean ages of the normal 12- to 15-month-old children and the children immunized after systemic H. influenzae type b disease were not different. About half the children in the sickle cell and in the normal 17- to 24-month-old groups received the same lot of PRP-T. The same lot of PRP-T was given to 11 (65%) of the 17 children with a history ofH. influenzae type b infection and to 45 (92%) of the 49 normal 12- to 15-month-old children. The mean age of children with a history of systemic H. influenzae type b disease was 9.4 + 5.7 months (range 3 to 19 months) at the time of hospital admission. All but one child had meningitis. We did not attempt to match our patients with malignancies, who were generally older than children in the other groups, with normal children of the same age. Of the 18 Children in this group, 13 had leukemia. Of the 13 children with acute lymphocytic leukemia, 10 received therapy with methotrexate and VP-16. Eleven children overall and 7 of 13 with leukemia had begun receiving maintenance chemotherapy 12 months or less before PRP-T immunization. There were no differences in the geometric mean titer or in the proportion of children having >1 #g/ml anti-PRP antibody before immunization between the group of normal 12- to 15-month-old infants and the group with previous H. influenzae type b infection (Table). However, a higher proportion of preimmunization sera contained anti-PRP antibody levels >0.15 #g/ml in children who had had H. influenzae type b infection (p = 0.008). After one or two doses of PRP-T there were no differences in anti-PRP antibody responses between these two groups. In the group who had had H. influenzae type b disease, the two children with anti-PRP antibody concentrations 1 #g/ml after a single immunization. Five of six children with preimmunization anti-PRP antibody levels _>0.15 ~g/ml responded to PRP-T with a rise in antibody titer to > 1 /~g/ml (one child did not have an increase of preexisting titer) compared with only 4 of 12 children with prevaccination concentrations
The three licensed Haemophilus influenzae type b polyribosylribitol phosphate-protein conjugate vaccines (PRPdiphtheria toxoid, PRP-outer-membrane protein complex of Neisseria meningitidis, oligosaccharide-CRM197) are more immunogenic than PRP alone in children with sickle Supported by Pasteur Merieux Serum and Vaccines, Connaught Laboratories Inc., Swiftwater, Pa. Submitted for publication Sept. 9, 1991; accepted Nov. 4, 1991. Reprint requests: Sheldon L. Kaplan, MD, Infectious Disease Service, Texas Children's Hospital, Clinical Care Center, Mail Code 3-2371, 662l Fannin, Houston, TX 77030. 9/22/34793
cell anemia l4 or malignancies,5-7 or after systemic H. influenzae type b infection,s-l~ Furthermore, children who have had systemic H. influenzae type b infection despite PRP vaccination generally have protective levels of antiPRP PRP-D PRP-T
Polyribosylribitolphosphate PRP-diphtheria toxoid conjugate vaccine PRP-tetanus toxoid conjugate vaccine
PRP antibody after a vaccination with H. influenzae type b PRP-protein conjugate vaccine, l 1, 12 A fourth, unlicensed H. influenzae type b conjugate vaccine consists of H. influenzae type b capsular polysaccha-
367
368
Kaplan et al.
The Journal of Pediatrics March 1992
T a b l e . Polyribosylribitol phosphate antibody titer after vaccination with polyribosylribitol phosphate-tetanus toxoid conjugate
Group
N
Mean a g e at first dose (too)
Normal (12-15 mo.) Systemic 14. influenzae type b infection* Malignancy Sickle cell anemia Normal (17-24 mo)
49 17 18 19 16
12.5 + 0.5 11.9 _+ 5.2 43.1 _+ 18.3 18.3 +_ 15.1 20.4 + 2.5
Geometric mean titer (pg/ml) Before
0.08 (2/49) 0.14 (3/17) 0.14 (2/18) 0.10 (1/19) 0.16 (1/15)
[4] [6]? [6] [3] [5]
After I dose
After 2 doses
3.1 (36/48) 5.6 (15/17) 1.4 (9/18) 4.8 (14/19) 6.9 (14/16)
12.0 (47/49) 12.6 (10/10) 0.4 (1/2) 14.2 (8/9) --
Proportionwith PRP antibodyconcentrations>~1~g/ml givenin parentheses.Numberwith PRP antibodyconcentrations>0. l 5 tLg/mlgivenin brackets. *SystemicH. influenzaetype b infectioninvolvedmeningitisin 16 and arthritis in 1. tFor normal 12- to 15-month-oldchildrenversusthose with previousH. influenzae type b infections,p = 0,008
ride linked to tetanus protein. This vaccine has proved highly immunogenic in young infants) 3' 14 In comparative trials in which different H. influenzae type b conjugate vaccines were evaluated within the same population and antibodies were determined by the same assay, PRP-T resulted in higher tevels of antibody to PRP than did other conjugate vaccines, ls17 Sarnaik et al) 8 immunized 25 children with sickle cell anemia between 2 and 5 years of age with PRP-T; 5 of 25 children before and all of 23 after a single dose of PRP-T had > 1.0 #g/ml of PRP antibody. In this study we evaluated the immunogenicity of PRP-T in children with sickle cell anemia or malignancies and after systemic H. influenzae type b infection. METHODS Vaccine. The H. influenzae type b PRP-T was provided by Pasteur Merieux Company (Connaught Laboratories Inc., Swiftwater, Pa.). Each dose contained 10 #g purified H. influenzae type b capsular polysaccharide and 20 #g purified tetanus protein derived from the detoxifled tetanus toxoid. Lyophilized conjugate vaccine was reconstituted with 0.4% saline solution and administered intramuscularly in the thigh. Five different lots of PRP-T were administered during the study. Subjects. Three patient groups were sought for enrollment in this study as follows: (1) children younger than 20 months of age after systemic 1t. influenzae type b infection who were hospitalized at Texas Children's Hospital (all had H. influenzae type b isolated from cultures of blood, cerebrospinal fluid, or both), (2) children with sickle cell anemia who were younger than 5 years of age and who were being followed in the pediatric hematology clinic at Baylor College of Medicine, and (3) children with malignancies who were receiving maintenance chemotherapy. Exclusions for enrollment in the study included (1) previous immunization with an H. influenzae type b vaccine, (2) history of severe reaction to diphtheria-pertussis-tetanus vaccine or diphtheria-tetanus toxoid, (3) receipt of immune globulin or whole blood within the previous 3 months, (4) platelet count
less than 50,000 cells/mm 3 in children with malignancies, and (5) major cardiac anomaly or epilepsy. Normal children in two different age groups (17 to 24 months and 12 to 15 months) who were followed in the private office of one of the investigators (D.M.S.) were enrolled in PRP-T studies being conducted concomitantIy with the PRP-T studies in the at-risk patient populations. Sera from 16 of 100 normal children, 17 to 24 months of age and immunized with a single dose of PRP-T, were available for analysis. Sera from 49 normal children, 12 to 15 months of age and immunized with two doses of PRP-T, also were available for analysis. The protocol was approved by the institutional review boards of Baylor College of Medicine and Texas Children's Hospital. Informed parental consent and consent of the patient's private physician were obtained before any child's enrollment in the study. Vaccine schedule. Children in the three patient groups who were younger than 18 months of age at initial immunization received two doses of PRP-T separated by 2 months. Children in the three patient groups who were l 8 months of age or older received one dose of PRP-T. Children with sickle cell anemia received three doses of PRP-T if immunized before 6 months of age. Serum was obtained before and after each dose and 1 to 2 months after the final dose. Children with a recent history of systemic H. influenzae type b infection were immunized at least 1 month after discharge and bad to have received at least two doses of diphtheria-pertussis-tetanus vaccine before PRP-T immunization. Antibody assay. Total serum PRP antibody concentrations for all sera were measured by a radioantigen binding assay performed by Connaught Laboratories. The reference serum for this assay is FDA Hib antibody (lot 1983). The lower limit of detection for the assay was 0.06 ~g/ml. Sera with nondeteetable levels of anti-PRP antibody were assigned a value of 0.06 ~zg/ml for analysis. Statistical analysis. Comparisons among groups were performed by means of analysis of variance and the Student
Volume 120 Number 3
Immunogenicity of Hib-tetanus vaccine in at-risk children
t test. The proportion of children with levels of antibody to PRP _>0.15 #g/ml or > 1 #g/ml was analyzed by the Fisher Exact Test. RESULTS The number of children in each category receiving PRP-T is shown in the Table. The mean ages of the normal children 17 to 24 months of age and the children with sickle cell anemia were not significantly different. Similarly, the mean ages of the normal 12- to 15-month-old children and the children immunized after systemic H. influenzae type b disease were not different. About half the children in the sickle cell and in the normal 17- to 24-month-old groups received the same lot of PRP-T. The same lot of PRP-T was given to 11 (65%) of the 17 children with a history ofH. influenzae type b infection and to 45 (92%) of the 49 normal 12- to 15-month-old children. The mean age of children with a history of systemic H. influenzae type b disease was 9.4 + 5.7 months (range 3 to 19 months) at the time of hospital admission. All but one child had meningitis. We did not attempt to match our patients with malignancies, who were generally older than children in the other groups, with normal children of the same age. Of the 18 Children in this group, 13 had leukemia. Of the 13 children with acute lymphocytic leukemia, 10 received therapy with methotrexate and VP-16. Eleven children overall and 7 of 13 with leukemia had begun receiving maintenance chemotherapy 12 months or less before PRP-T immunization. There were no differences in the geometric mean titer or in the proportion of children having >1 #g/ml anti-PRP antibody before immunization between the group of normal 12- to 15-month-old infants and the group with previous H. influenzae type b infection (Table). However, a higher proportion of preimmunization sera contained anti-PRP antibody levels >0.15 #g/ml in children who had had H. influenzae type b infection (p = 0.008). After one or two doses of PRP-T there were no differences in anti-PRP antibody responses between these two groups. In the group who had had H. influenzae type b disease, the two children with anti-PRP antibody concentrations 1 #g/ml after a single immunization. Five of six children with preimmunization anti-PRP antibody levels _>0.15 ~g/ml responded to PRP-T with a rise in antibody titer to > 1 /~g/ml (one child did not have an increase of preexisting titer) compared with only 4 of 12 children with prevaccination concentrations
