Hib vaccine administered as a single injection vs DTPa–HBV and Hib vaccines administered simultaneously at separate sites, to infants at 2, 4 and 6 months of age

Vaccine 19 (2001) 4260– 4266 www.elsevier.com/locate/vaccine

Reactogenicity of DTPa–HBV/Hib vaccine administered as a single injection vs DTPa–HBV and Hib vaccines administered simultaneously at separate sites, to infants at 2, 4 and 6 months of age F. Omen˜aca a, R. Dal-Re´ b,*, V. D’Apuzzo c, C. Kattamis d, H.P. Gnehm e, J. Garcı´a-Sicilia a, P. Garcı´a-Corbeira b, for The European DTPa – HBV/Hib 041 Study Group 1 b

a Departments of Neonatology and Paediatrics, La Paz Hospital, Madrid, Spain Medical Department, SmithKline Beecham Pharmaceuticals, c/Dr Se6ero Ochoa 2, 28760 Tres Cantos, Madrid, Spain c Beata Vergine Regional Hospital, Mendrisio, Switzerland d First Department of Paediatrics, Athens Uni6ersity, St. Sophia Children’s Hospital, Athens, Greece e Paediatric Clinic, Cantonal Hospital, Aarau, Switzerland

Received 30 November 2000; received in revised form 9 April 2001; accepted 11 April 2001

Abstract An open, randomised, multicentre trial was performed to assess the reactogenicity and safety profile of the administration of a candidate Haemophilus influenzae type b (Hib) conjugate vaccine with a quadrivalent diphtheria– tetanus– acellular pertussis– hepatitis B (DTPa–HBV) vaccine as a single injection (Group 1) versus the simultaneous administration of the latter vaccine (DTPa–HBV) and an available Hib conjugate vaccine (Group 2) in opposite thighs, as a primary vaccination course to healthy infants at 2, 4 and 6 months of age. Eight hundred and eighty five infants (9.3 9 1.4 weeks old) were randomly allocated to Group 1 (n =665) and Group 2 (n=221). Oral polio vaccine was given concomitantly to all subjects. Blood samples (pre-vaccination and 1 month after the third dose) were obtained from a subset of infants (Group 1, 73; Group 2, 22) for serological determinations. Local and general symptoms were recorded by parents on diary cards. 2614 diary cards (Group 1, 1966; Group 2, 648) were collected. There were no statistically significant differences in the incidence of local and general symptoms between groups. Pain such that the infant cried when limb was moved was reported in 0.6 and 0.2% in groups 1 and 2, respectively. Redness and swelling ( \ 20 mm in diameter) were recorded between 2.1 and 3% in both groups. Fussiness preventing normal activities was the most frequently reported general symptom in both groups (1.6 and 1.9% in groups 1 and 2, respectively). Fever (rectal temperature \ 39.5°C) was reported in 0.4% (Group 1) and 0.3% (Group 2). All subjects included in the immunogenicity analysis had seroprotective or seropositive titres to the diphtheria, tetanus, hepatitis B and pertussis components of the vaccines. About 99 and 100% of infants had anti-PRP titres ]0.15 mcg/ml in groups 1 and 2, respectively. This study indicates that DTPa– HBV vaccine

Abbre6iations: DTPa, diphtheria–tetanus–acellular pertussis vaccine; ELISA, enzyme-linked immunosorbent assay; FHA, filamentous hemagglutinin; GMT, geometric mean titres; HBV, hepatitis B virus; Hib, Haemophilus influenzae type b conjugate vaccine; IPV, inactivated poliovirus; OPV, live attenuated poliovirus; PRN, pertactin; PRP, poliribosylribitol phosphate; PT, pertussis toxin. * Corresponding author. E-mail address: [email protected] (R. Dal-Re´). 1 Other members of The European DTPa-HBV/Hib 041 Study Group; Greece; Professor N. Beratis (University Hospital of Rion, Patras), Assoc. Professor E. Mantzourani (University Hospital of Iraklion, Iraklion), Assoc. Professor F. Kanakoudi-Tsakalidou (Aristotle University, Ippokration Hospital, Thessaloniki), Switzerland; Dr P. Birrer (Ittigen), Dr D. Desgrandchamps (Centre for Infectology and Vaccinology, Basel), Dr H. Oswald (Cantonal Hospital, Winterthur), Dr C.A. Siegrist (WHO Collaborating Centre for Vaccinology and Neonatal Immunology, University of Geneve, Geneve), Dr B. Vaudaux (Lausanne). Study supported by a grant from SmithKline Beecham Biologicals, Rixensart, Belgium. 0264-410X/01/$ - see front matter © 2001 Published by Elsevier Science Ltd. PII: S0264-410X(01)00149-9

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given in a single injection with a candidate Hib conjugate vaccine has a similar reactogenicity profile to that of two commercially available vaccines (DTPa –HBV, Hib) given in two simultaneous injections to infants 2, 4 and 6 months of age. © 2001 Published by Elsevier Science Ltd. Keywords: Reactogenicity; Infants; Primary course; Haemophilus influenzae type b conjugate vaccine; Quadrivalent (DTPa – HBV) vaccine; One injection

1. Introduction Delivering multiple vaccine antigens in a single injection is considered a priority for health care providers and parents [1]. In the last decade, a substantial effort has been made by manufacturers and investigators to develop new combined vaccines targeted to infants. The paediatric vaccination schedules recommended in an increasing number of developed countries include immunisation against diphtheria–tetanus – Bordetella pertussis (by means of acellular pertussis vaccines, DTPa), hepatitis B (HBV), Haemophilus influenzae conjugate type b (Hib) and poliovirus (inactivated, IPV, or live attenuated, OPV) vaccines [2,3]. Currently several combined vaccines are available which include some of the mentioned antigens, (e.g. DTPa– IPV, DTPa/Hib, DTPa – HBV, DTPa –IPV/Hib) [4,5]. After the inclusion of Hib conjugate vaccines into the infant immunisation schedules of several countries, it was shown to be highly effective in reducing the incidence of invasive Hib disease [6]. However, reduction in anti-PRP antibody titres was observed when Hib conjugate vaccine was administered in a single injection with DTPa, when compared with responses of infants who received both vaccines simultaneously but at separate sites [6,7]. However, the lower antibody responses have not been associated with functional impairment nor has there been a decrease in the induction of immune memory against Hib [8]. The present study was conducted to compare the safety and reactogenicity over the primary vaccination course to infants of the administration of a candidate Hib conjugate vaccine with DTPa– HBV in a single injection with that of an available Hib conjugate vaccine administered simultaneously with the same DTPa– HBV vaccine, in opposite limbs.

2. Materials and methods

2.1. Study population The study was conducted between August 1997 and February 1999, in healthy infants aged 8– 12 weeks at the time of first vaccination, who were recruited in 11 centres from Greece, Spain and Switzerland. Subjects were ineligible for study if they had earlier history of diphtheria, tetanus, pertussis, hepatitis B and/or Hib vaccination or disease. Infants were excluded from the study (at study

entry and at each following visit) if; (a) they had an allergic disease likely to be stimulated by the vaccination, or any suspected or confirmed immunosuppressive condition (including HIV infection); (b) intercurrent diphtheria, tetanus, pertussis, hepatitis B and/or Hib disease; (c) acute febrile illness at the time of planned vaccination (which warranted deferral of the vaccination pending recovery); (d) major congenital defects, or serious chronic illness or progressive neurological disease; (e) administration of immunosuppressive therapy (except for topical corticosteroids); (f) administration of immunoglobulin or any blood products within 2 months before enrolment or during the study period; and (g) administration of any vaccine (except for OPV) and of any experimental drug or vaccine within 30 days before entering the study or during the study period.

2.2. Study design and objecti6es This was an open, randomised, multicentre, comparative phase III clinical trial with two groups of healthy infants. The randomisation was made using an algorithm of pseudorandom numbers (given by RS/1 from BBN Inc.). Subjects were allocated to the two groups according to a 3:1 ratio. Group 1 received the candidate Hib conjugate vaccine mixed with DTPa–HBV combined vaccine in a single injection in the left thigh; Group 2 (control group) received an available Hib conjugate vaccine (right thigh) given simultaneously with DTPa– HBV vaccine (left thigh). All infants received OPV vaccine. The study protocol was approved by the Research Ethics Committees of the centres involved, and was conducted following the Good Clinical Practice guidelines. Written informed consent was obtained from the parents or guardians prior to enrolment. The primary objective was to assess the comparability of the two groups with respect to the frequency of solicited symptoms over the full vaccination course (three doses). In addition, the secondary endpoints were to evaluate the frequency of unsolicited general symptoms in the two groups, and to assess the immunogenicity in a subset of subjects (whose parents agreed to blood sampling) to each of the seven antigens, i.e. Hib polysaccharide polyribosylribitol phosphate (PRP), diphtheria toxoid, tetanus toxoid, three pertussis antigens (Pertussis toxin, PT; Filamentous Hemagglutinin, FHA; Pertactin, PRN) and HBV. Two blood samplings (before the first dose and 1 month after the third dose) were obtained from these infants, all of them recruited in Greece.

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All vaccines were administered intramuscularly at 2, 4, 6 months of age. All vaccines were closely monitored for at least 15 min after each dose. Solicited local reactions (pain, swelling and redness at the injection site) and general symptoms (fever, rectal temperature ]38°C; fussiness; vomiting; diarrhoea; loss of appetite; restlessness and sleepiness) were recorded on diary cards by the parents on the day of vaccination, and on each of the 3 subsequent days, and returned to the investigator at the next visit. General symptoms other than fever were assessed by the parents as grade 1 (easily tolerated), grade 2 (sufficient to interfere daily activities) or grade 3 (sufficient to prevent normal activity). Fever\ 39.5°C was considered as grade 3. Pain was rated by parents as grade 1 (minor reaction to touch), grade 2 (cries to touch) and grade 3 (cries when the limb is moved). Redness and swelling were measured and recorded (\ 20 mm in diameter were considered as grade 3). In group 2, a local reaction reported at both injection sites would be counted once. When reactions differed in intensity, the highest intensity was considered. Any symptoms not specifically solicited were classified as unsolicited symptoms; this included all solicited symptoms appearing after the 4-day follow-up period. All adverse experiences were recorded and assessed until the last visit, which was performed 30 to 35 days after the third vaccine dose. Causality assessment (‘not related’, ‘unlikely’, ‘suspected’ and ‘probable’) of solicited and unsolicited adverse experiences were made by the investigator; local solicited symptoms, however, were always considered as ‘related’ to vaccination. The following adverse experiences associated with pertussis immunisation would have constituted absolute contraindication or precautions to further administration of pertussis vaccine; contraindications: hypersensitivity reaction due to the vaccine and development of encephalopathy within 7 days of vaccination; precautions: rectal temperature] 40.5°C or collapse or shock-like state (hypotonic-hyporesponsive episode) within 48 h of vaccination, seizures within 3 days of vaccination, and persistent, inconsolable screaming or crying for more than 3 h within 48 h of vaccination.

2.3. Study 6accines All vaccines were manufactured by SmithKline Beecham Biologicals (Rixensart, Belgium). OPV vaccine was provided for all infants. Each 0.5 ml dose of DTPa –HBV vaccine (lot no. 16729A2) contained 25 mg PT, 25 mg FHA, 8 mg PRN, ]30 IU diphtheria toxoid, ] 40 IU tetanus toxoid and 10 mg HBV surface antigen. Each 0.5 ml dose of Hib vaccine (lot no. HIB029A44/M) contained 10 mg PRP conjugated to : 30 mg tetanus toxoid. The candidate Hib vaccine

(lot no. DHIB031A42) contained 10 mg PRP conjugated to : 30 mg tetanus toxoid adsorbed onto aluminium salts. Only one lot of each of these vaccines was used.

2.4. Serological analyses All blood samples were labelled and maintained at − 20°C until serological analyses were performed at SmithKline Beecham Biologicals (Rixensart, Belgium) in a blinded fashion. Antibodies against diphtheria and tetanus toxoids were measured by enzyme-linked immunosorbent assay (ELISA) techniques, with a cutoff level of 0.1 IU/ml [9,10]. Antibodies (IgG) against PT, FHA and PRN, were measured by ELISA with a cut-off of 5 ELISA units (EL.U)/ml [11]. The assay was calibrated using the pooled US FDA reference sera (lot 3 for PT and FHA; lot 4 for PRN). AntiHBs antibody titres were determined using a commercially available radioimmunoassay kit (AUSAB, Abbott Laboratories, Chicago, IL) with a cut-off of 10 mIU/ml. Titres]10 mIU/ml are considered as protective [12]. Total antibodies to Hib PRP were measured by radiolabelled antigen binding assay [13], with a cut-off of 0.15 mg/ml [14].

2.5. Sample size and statistical analysis The objective was to compare the frequency of solicited symptoms over a full vaccination course in 600 evaluable group 1 subjects and 200 evaluable group 2 subjects (control group). Assuming a drop-out rate of 10.5%, 896 infants (Group 1, 672; Group 2, 224) should be enrolled. A subset of subjects whose parents accepted blood sampling were evaluated for immunogenicity. All infants were evaluated for reactogenicity. For each solicited symptom the percentage of doses with symptom occurrence over a 4-day follow-up period was calculated by group and compared between groups using a two-sided Fisher’s exact text. Due to the small number of cases with blood sampling in group 2, no statistical analysis was performed with the immunogenicity data; however, seroconversion rates and Geometric Mean Titres (GMT) were calculated, with 95% confidence interval (CI) for all vaccine components. For the purposes of GMT calculation, when a serological result was below the antibody assay detection cut-off, half the cut-off was used to quantify antibody titre. Significance was assumed at PB 0.05. The Bonferroni method was used to adjust P-values on multiple comparisons [15]. All statistical analyses were carried out using EPIINFO 6.02 software (CDC, Atlanta, GA, USA).

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3. Results A total of 885 infants (Group 1, 664; Group 2, 221) were enrolled, of whom 855 (Group 1, 643; Group 2, 212) completed the full vaccination course at 2, 4 and 6 months of age. OPV vaccine was given simultaneously. Thirty infants did not complete the study due to migration from study area (n = 6), consent withdrawal (five cases), protocol violation (three cases), vaccination course not completed (three cases), or other reasons (ten cases). Three infants were lost to follow up; two (from group 1) were lost for post-vaccination blood sampling, and one (from group 2) due to a serious adverse event (obstructive bronchitis; the child recovered; event considered by the investigator as ‘not related’ to the study vaccines). The immunogenicity subset comprised 95 infants; 73 in group 1, and 22 in group 2. The mean age (9 S.D.) and the female/male ratio of the study population was 9.39 1.4 weeks old (range; 5– 16) and 1.06/1, respectively. For treatment of incidental illnesses a variety of concomitant medications (compatible with protocol criteria) were given to infants during this trial, such as antibiotics, bronchodilators, mucolytics and cough suppressants.

3.1. Reactogenicity and safety analysis Two thousand six hundred and fourteen diary cards were returned (Group 1, 1966; Group 2, 648). Only 34.6% (Group 1) and 35.2% (Group 2) of all doses were not associated with any local or general symptom along the study. In both groups the incidence of any local reaction and any general symptom decreased with each subsequent dose, in group 1, 70.6, 66.0 and 59.4% after the first, second and third dose, respectively, and in group 2, 71.2, 64.7 and 58.4% after the first, second and third dose, respectively. During the whole study, 38.1%

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(95% CI, 35.9–40.3) of diary cards in group 1 and 36.7% (95% CI, 33–40.6) in group 2, reported local (solicited and unsolicited) reactions at the injection site, whereas 55.3% (95% CI, 53.1–57.5) in group 1 and 53.9% (95% CI, 49.9– 57.7) in group 2, reported at least one general symptom. Table 1 shows the incidences of local solicited symptoms and those considered as grade 3 during the 4-day follow-up period after all doses by vaccine, (i.e. injection site). Local reaction reported at both injection sites was counted once. There were no statistically significant differences between groups in the incidence of local reactions. Table 2 shows the total incidence of all and grade 3 solicited general symptoms during the 4-day follow-up period after all doses by group. There were no statistically significant differences in the incidence of each of the solicited general symptoms between groups. The onset of almost all symptoms occurred within the first 48 h after vaccination. The vast majority were described as mild or moderate, and resolved within 48 h. Only 18 serious adverse events were reported during the course of the study, 17 of which were reported as ‘not related’/‘unlikely’ to be related to vaccination. The remaining one was assessed as ‘suspected’/‘possibly’ related. This was an infant (from group 1) who developed a generalised atopic eczema 3 days after receiving the second DTPa– HBV/Hib dose; the subject recovered and received the third dose with no problem. A total of 22 (Group 1, 13; Group 2, 9) unsolicited local and general symptoms were reported during the 30 days after vaccination in the diary cards collected (n= 2614). There were six cases of inflammation or mass at the injection site, eczema (two), fever (two), and one case of oedema, constipation, gastroenteritis, rhinitis, rash, urticaria and nervousness, among others. Paracetamol was prescribed for treatment of fever in

Table 1 Incidences of local solicited symptoms and those considered as grade 3 reported during the 4-day follow-up period after all doses by vaccine, from 2614 diary cards returned Symptom

Pain Redness Swelling

Grade

Total Grade 3 Total \20 mm Total

Group 2 (N= 648)a

Group 1 (N= 1966)

Group 2 (N =648)

DTPa-HBV/Hib

DTPa-HBV

n (%)

95% CI

n (%)

95% CI

n (%)

95% CI

n (%)

95% CI

358 11 533 41 374 59

16.5–20.0 0.3–1.0 25.2–29.1 1.5–2.8 17.3–20.8 2.3–3.9

78 0 157 14 123 19

9.6–14.8 0.0–0.6 21.0–27.7 1.2–3.6 16.0–22.2 1.8–4.5

55 (8.5) 0.0 (0) 98 (15.1) 10 (1.5) 58 (9) 7 (1.1)

6.5–10.9 0.0–0.6 12.5–18.1 0.7–2.8 6.9–11.4 0.4–2.2

92 1 178 18 137 23

11.6–17.1 0.0–0.9 24.1–31.1 1.7–4.4 18.1–24.5 2.3–5.3

(18.2) (0.6) (27.1) (2.1) (19) (3)

(12) (0) (24.2) (2.2) (19) (2.9)

Hib

DTPa-HBV+Hib

(14.2) (0.2) (27.5) (2.8) (21.1) (3.5)

Group 1; DTPa-HBV/Hib (single injection), Group 2; DTPa–HBV+Hib (two injections in opposite limbs), N; total number of diary cards returned following all doses, n; total number of a solicited local symptom following all doses, Total; all specified reactions reported during the follow-up period, Grade 3 pain; pain such that the infant cries when limb is moved. a Local reactions reported at both injections sites were counted once.

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Table 2 Incidences of all solicited general symptoms and those considered as grade 3 during the 4-day follow-up period after all doses by group, from 2614 diary cards returned Symptom

Diarrhoea Fever Fussiness Loss of appetite Restlessness Sleeping more than usual Vomiting

Intensity

Total Grade 3 Total \39.5°C Total Grade 3 Total Grade 3 Total Grade 3 Total Grade 3 Total Grade 3

Group 1 (N= 1966)

Group 2 (N= 648)

DTPa–HBV/Hib

DTPa–HBV+Hib

n

%

95% CI

n

%

95% CI

185 7 301 7 563 31 297 9 396 26 428 11 163 5

9.4 0.4 15.3 0.4 28.6 1.6 15.1 0.5 20.1 1.3 21.8 0.6 8.3 0.3

8.2–10.8 0.1–0.7 13.7–17.0 0.1–0.7 26.6–30.7 1.1–2.2 13.6–16.8 0.2–0.9 18.4–22.0 0.9–1.9 20.0–23.7 0.3–1.0 7.1–9.6 0.1–0.6

53 0 87 2 187 12 79 1 139 6 146 3 56 1

8.2 0 13.4 0.3 28.9 1.9 12.2 0.2 21.5 0.9 22.5 0.5 8.6 0.2

6.2–10.6 0.0–0.6 10.9–16.3 0.0–1.1 25.4–32.5 1.0–3.2 9.8–15.0 0.0–0.9 18.3–24.8 0.3–2.0 19.4–25.9 0.1–1.3 6.6–11.1 0.0–0.9

Group 1; DTPa–HBV/Hib (single injection), Group 2; DTPa–HBV+Hib (two injections in opposite limbs), N; total number of diary cards returned following all doses, n; total number of a solicited general symptom following all doses, Total; all reports of a solicited general symptom, irrespective of the relationship to vaccination, Grade 3; symptom sufficient to prevent normal activity.

153 subjects (Group 1, 115; Group 2, 38) after administering 197 vaccine doses (Group 1, 143; Group 2, 54). Treatment with paracetamol lasted548 h after 74 and 57% of doses administered in groups 1 (median; 24 h) and 2 (median; 48 h), respectively. Other antipyretics prescribed were ibuprofen (three cases), mefenamic acid (five cases) and dipyrone (one case). Paracetamol was prescribed as prophylactic treatment in 13 infants (20 doses) and two cases (two doses) in groups 1 and 2, respectively.

3.2. Immunogenicity analysis Tables 3– 5 show the immunogenicity results (seroprotective or seropositivity rates and GMTs) for antidiphtheria, anti-tetanus, anti-HBs, anti-PRP, anti-PT, anti-FHA and anti-PRN, both pre- and post-vaccination. Only descriptive data are shown. It should be mentioned, however, that 100% seroprotective rates (with similar GMTs) were obtained in both groups after vaccination for diphtheria, tetanus, and hepatitis B; this was also the case for the three B. pertussis antigens (100% seropositive rates). As far as Hib component is concerned, 1 month after vaccination all subjects (except one in group 1) had anti-PRP]0.15 mcg/ml, whereas 84% (95% CI, 73.3– 91.8) and 100% (95% CI, 80.5–100) had anti-PRP] 1.0 mcg/ml in group 1 and group 2, respectively; GMTs were much higher in group 2 (22.230 mcg/ml) than in group 1 (4.641 mcg/ml).

4. Discussion DTPa vaccines are increasingly recommended in developed countries as primary vaccination course for infants. Since HBV and Hib conjugate vaccines are also included in routine immunisation programmes in such Table 3 Seroprotective rates (%) and geometric mean titres (GMT) for antidiphtheria and anti-tetanus antibodies by group. ]0.1 IU/ml, n (%)

GMT (95% CI)

Anti-diphtheria Group 1 (59) Pre Group 2 (19)

10 (16.9)

Anti-diphtheria Group 1 (64) Post Group 2 (16)

64 (100)

0.065 (0.055–0.076) 0.072 (0.050–0.104) 2.615 (2.225–3.073) 2.440 (1.755–3.394) 0.101 (0.078–2.779) 0.114 (0.069–0.188) 3.279 (2.779–3.869) 3.873 (2.991–5.015)

Antibody Timing

Anti-tetanus Pre

Anti-tetanus Post

Group (N)

4 (21.1)

16 (100)

Group 1 (59)

24 (40.7)

Group 2 (19)

9 (47.4)

Group 1(64)

64 (100)

Group 2 (16)

16 (100)

Group 1; DTPa–HBV/Hib (single injection), Group 2; DTPa–HBV+ Hib (two injections in opposite limbs), N; total number of subjects tested, n; number of subjects with titres]cut-off value, Pre; pre-vaccination, Post; 1 month after administration of the third dose.

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Table 4 Seroprotective rates (%) and geometric mean titres (GMT) for anti-HBs and anti-PRP antibodies per group. Group (N)

]10 mIU/ml, n (%)

Anti-HBS Pre Group Group Post Group Group

1 2 1 2

(70) (21) (69) (17)

12 2 69 17

Anti-PRP Pre Group Group Post Group Group

1 2 1 2

(70) (21) (69) (17)

– – – –

(17.1) (9.5) (100) (100)

]0.15 mcg/ml, n (%)

– – – – 26 7 68 17

]0.5 mcg/ml, n (%)

– – – – (37.1) (33.3) (98.6) (100)

12 1 64 17

]1.0 mcg/ml, n (%)

– – – – (17.1) (4.8) (92.8) (100)

8 0 58 17

GMT (95% CI)

8.6 (6.3–11.7) 5.8 (4.7–7.3) 1177.9 (888.5–1561.4) 1406.2 (658.5–3002.8) (11.4) (0.0) (84.1) (100)

0.157 (0.120–0.206) 0.124 (0.087–0.177) 4.641 (3.204–6.724) 22.230 (14.464–34.165)

Group 1; DTPa–HBV/Hib (single injection), Group 2; DTPa–HBV+Hib (two injections in opposite limbs), N; total number of subjects tested, n; number of subjects with titres]cut-off value, Pre; pre-vaccination, Post; 1 month after administration of the third dose.

countries, the possibility of administering these vaccines in one injection would enhance parent acceptability thus helping to increase vaccine coverage among infants. Currently, a number of newly developed vaccines are available in a number of countries. This study shows that DTPa –HBV given in a single injection with a candidate Hib conjugate vaccine has a similar reactogenicity profile to that of two commercially available vaccines (DTPa–HBV, Hib) given in two simultaneous injections to infants at 2, 4 and 6 months of age. This was also shown in a earlier study [16]. This study comprised a large number of patients and doses; a total of 2614 diary cards were collected. Local or general symptoms were more frequently observed after the first doses than after subsequent ones, a finding also reported by other investigators when DTPa –HBV was given in one injection with the same available Hib conjugate vaccine used in group 2 [17]. Redness was the most commonly reported local symptom in both groups (:27%), but higher than that reported in another study (13%; DTPa– HBV/Hib in one injection) in which the Hib vaccine used was the one used in group 2 [17], and that shown after three doses of DTPa (20%) [18]. Pain at the injection site was reported in 18% (0.6% were grade 3) and 14% (0.2%, grade 3) of diary cards of groups 1 and 2, respectively. In the earlier mentioned study [17], pain was reported in 16% of cases (being 0.2% graded as ‘severe’). Fussiness was the most frequently general symptom recorded (c. 29%) in both groups. Fever (rectal; \ 38°C), considered to be the most clinically relevant general symptom, was reported in 15 and 13% of all diary cards in groups 1 and 2, respectively. Fever was\ 39.5°C after only seven (0.4%) and two (0.3%) of doses in groups 1 and 2, respectively, these figures being similar to that observed when DTPa is given as primary vaccination (0.5% on an 8-day post-vaccination follow-up) [18]. These incidences are similar (or lower) to those observed in other

studies with DTPa–HBV/Hib [17] and DTPa–IPV – Hib [19]. The similarity in incidence of clinical reactions observed between the two groups, strongly suggests that there is no cumulative increase in reactogenicity in combining DTPa–HBV/Hib in one injection, compared with simultaneous administration of DTPa–HBV and Hib at different sites. Table 5 Seropositivity rates (%) and geometric mean titres (GMT) for antiPT, anti-FHA and anti-PRN antibodies per group Antibody Timing

Group (N)

]5 EL.U/ml, n (%)

GMT (95% CI)

Anti-PT Pre

Group 1 (59)

26 (44.1)

Group 2 (19)

7 (36.8)

Group 1 (64)

64 (100)

Group 2 (16)

16 (100)

Group 1 (59)

53 (89.8)

Group 2 (19)

16 (84.2)

Group 1 (64)

64 (100)

Group 2 (16)

16 (100)

Group 1 (59)

22 (37.3)

Group 2(19)

5 (26.3)

4.2 (3.5–4.9) 4.4 (2.9–6.5) 40.0 (34.4–46.4) 46.2 (32.2–66.4) 13.4 (9.9–18.2) 13.8 (6.9–27.6) 256.0 (220.1–297.7) 329.5 (254.8–426.1) 4.3 (3.5–5.3) 3.8 (2.5–5.5) 152.9 (127.0–184.1) 172.2 (128.0–231.7)

Post

Anti-FHA Pre

Post

Anti-PRN Pre

Post

Group 1 (64)

64 (100)

Group 2(16)

16 (100)

Group 1; DTPa–HBV/Hib (single injection), Group 2; DTPa–HBV+ Hib (two injections in opposite limbs), PT; Pertussis toxin, FHA; Filamentous Hemagglutinin, PRN; Pertactin, N; total number of subjects tested, n; number of subjects with titres]cut-off value, Pre; pre-vaccination, Post; 1 month after administration of the third dose.

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The limited sample size of the immunogenicity results places a limitation on the conclusions that can be drawn. In a earlier study, 183 infants were randomised to receive the same vaccines as those used in this study at 1.5, 3 and 5 months of age [16]. Compared with GMTs obtained in this study, those observed in the earlier [16] were slightly lower except for anti-HBs; in both groups]95% of infants had anti-PRP levels] 0.15 mcg/ml, with GMTs of 1.27 and 2.27 mcg/ml when DTPa –HBV/Hib and DTPa – HBV +Hib were given, respectively. In any case, it should be mentioned that in this study and in both groups the seroprotection or seropositive rates and GMTs obtained were similar for diphtheria, tetanus, hepatitis B and pertussis, and comparable to those found in other studies with available vaccines (DTPa, DTPa– HBV, DTPa – IPV – Hib) [7,19 –21]. The anti-PRP antibody response observed in this study, in group 1 is very similar to that observed by Aristegui et al. [17]. These results are similar or higher than those found with three-dose primary course of four available PRP-conjugate vaccines [22]. Furthermore, recent data show that primary vaccination (3, 4, 5 months of age) with DTPa – HBV/Hib vaccines, given in one injection, induces immunological memory, relevant to protection against invasive Hib disease [23]. The results from this study suggest that the candidate Hib conjugate vaccine when given as a mixed administration with DTPa–HBV is adequately tolerated and has an acceptable immunogenicity profile when given to infants at 2, 4 and 6 months of age.

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