Safety and immunogenicity of an inactivated Vero cell_derived ...

Travel Medicine and Infectious Disease xxx (xxxx) xxx–xxx

Contents lists available at ScienceDirect

Travel Medicine and Infectious Disease journal homepage: www.elsevier.com/locate/tmaid

Safety and immunogenicity of an inactivated Vero cell_derived Japanese encephalitis vaccine (IXIARO®, JESPECT®) in a pediatric population in JE non-endemic countries: An uncontrolled, open-label phase 3 study Tomas Jelineka, Michael A. Cromerb, Jakob P. Cramerc, Deborah J. Millsd, Kenneth Lessanse, Anthony W. Gherardinf, Elizabeth D. Barnettg, Stefan H.F. Hagmannh, Helena H. Asklingi, Sigrid Kiermayrj, Vera Kadlecekj, Susanne Eder-Lingelbachj, Christian Taucherj,∗, Katrin L. Dubischarj a

Berlin Center for Travel & Tropical Diseases, Berlin and Institute of Medical Microbiology, Immunology and Hygiene, University of Cologne, Germany Tampa Clinical Research, Inc., Tampa, FL, USA c Takeda Pharmaceuticals International AG, Switzerland d Dr. Deb - The Travel Doctor, Brisbane, Queensland, Australia e Passport Health, Inc., Baltimore, MD, USA f The Travel Doctor – TMVC Pty Ltd, Melbourne Docklands, Victoria, Australia g Boston Medical Center, Section of Pediatric Infectious Diseases, Boston, MA, USA h Bronx - Lebanon Hospital Center, Division of Pediatric Infectious Diseases, New York, NY, USA i Karolinska Institutet, Dept. of Medicine, Unit for Infectious Diseases, Solna, Sweden j Valneva Austria GmbH, Campus Vienna Biocenter, Vienna, Austria b

A R T I C LE I N FO

A B S T R A C T

Keywords: Japanese encephalitis vaccine Immunogenicity Safety Children IXIARO

Background: Young travelers to South-East Asia may be at risk for Japanese encephalitis (JE). Methods: IXIARO® (0.25 ml or 0.5 ml, depending on age) were administrated to 100 travelers aged ≥ 2 months to < 18 years. Solicited AEs were collected for 7 days after each injection, unsolicited adverse events (AEs) for a total of 7 months. JE neutralizing antibodies were assessed in 64 subjects. Results: The most common solicited local AEs were redness (3/12 subjects), induration and tenderness (both 1/ 12) with 0.25 ml IXIARO®, and tenderness (44/88) and pain (22/88) with 0.5 ml IXIARO®. Common solicited systemic AEs were diarrhea (2/12) and loss of appetite (1/12) with 0.25 ml IXIARO® and muscle pain (27/88) and excessive fatigue (10/88) with 0.5 ml IXIARO®. In total, up to day 56, AEs were reported by 10/12 (83.3%) of subjects who received the 0.25 ml dose and 67/88 (76.1%) of those vaccinated with the 0.5 ml dose. All subjects (62/62; 100%) developed protective levels of JE neutralizing antibodies by Day 56 and 31/34 (91.2%) retained protective titers at Month 7. Conclusions: IXIARO® was generally well tolerated in children, with an overall AE profile similar to adults. IXIARO® was highly immunogenic in both dose groups.

1. Introduction Japanese encephalitis (JE) is the most common viral encephalitis in Asia and the Pacific Islands with about 68,000 cases estimated to occur per year by the World Health Organisation [1,2]. The JE virus (JEV) belongs to the family of Flaviviridae and is transmitted from viremic animals through infected Culicine mosquitos to humans. The clinical presentation of JE usually begins as a non-specific febrile illness including headache, sporadic coryza and gastrointestinal symptoms,

∗

which progresses to neurological symptoms including rigors, convulsions, meningitis/meningoencephalitis, or poliomyelitis-like illness. Only supportive care treatment is available [1,3]. While most infections are asymptomatic (< 1% of infections progress to clinical disease), clinical disease is very severe with a 30% case fatality rate, and 30%–50% of surviving patients suffering from neurologic or psychiatric sequelae [4,5]. In endemic regions JE is mainly a childhood disease. Most people in endemic regions are infected early in life, and in hyper-endemic areas the majority of disease burden affects

Corresponding author. Valneva Austria GmbH, Campus Vienna Biocenter 3, 1030 Vienna, Austria. E-mail address: [email protected] (C. Taucher).

https://doi.org/10.1016/j.tmaid.2018.03.003 Received 2 November 2017; Received in revised form 6 March 2018; Accepted 12 March 2018 1477-8939/ © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).

Please cite this article as: Jelinek, T., Travel Medicine and Infectious Disease (2018), https://doi.org/10.1016/j.tmaid.2018.03.003


T. Jelinek et al.

by local regulations. The Institutional Review Board (IRB) or the Independent Ethics Committee (IED) of each participating study site approved the study protocol and informed consent/assent form. The trial was registered on clinicaltrials.gov (NCT01047839). An independent Data Safety Monitoring Board (DSMB) was in place during the study and performed an interim safety review.

children below 10 years [6]. Vaccination has decreased the number of JE cases dramatically in several Asian countries [2], but because the virus is maintained in animal reservoirs, JE non-immune travelers remain at risk for infection in all endemic areas of South-East Asia [7]. Visiting rural and peri-urban areas, outdoor exposure, length of stay, and seasonal variation (i.e., mosquitoes becoming more active in the rainy season) are all risk factors for infection with JEV [8]. However, there are documented cases of JE that do not fulfil a typical at-risk profile, i.e. occurred outside the usual transmission months, during short trips, or in persons with limited backcountry/outdoor time. A careful review of itineraries and activities during travel is necessary to advise travelers appropriately about the risk for this disease [9]. Considering children are a prominent and vulnerable risk population, vaccination for children traveling from non-JEV endemic regions is recommended as an important preventive measure [7]. IXIARO® (IC51, Valneva Austria GmbH, Austria) is a purified, inactivated, Vero cell-derived JE vaccine first licensed in 2009 for adults. Pediatric licensure for use in travelers aged from 2 months upwards was granted in EU and US in 2013 [10,11]. This licensure was supported by a Phase 2 study [12], a large Phase 3 study conducted in a JE-endemic country that established a safety profile in children between 2 months and 17 years comparable to the control vaccines Prevnar® and HAVRIX® [13] as well as excellent immunogenicity with protective antibody titers in > 99% of subjects [14], and the present study. In this uncontrolled, open-label, Phase 3 study, safety and immunogenicity of IXIARO® were assessed in a ≥2 months to < 18 years old population consisting of previously JEV-unexposed travelers to JE endemic regions.

2.3. Vaccine IXIARO® (Valneva Austria, inactivated, alum-adjuvanted, Vero cellderived vaccine based on JEV strain SA14-14-2, lots JEV08K16, JEV09K35, JEV10H62, and JEV11H93, 0.25 ml for children < 3 years, 0.5 ml for children aged 3 years and above. The vaccine was provided as a pre-filled syringe attached without needle containing an 0.5 mL dose. For administration of the 0.25 mL dose, the syringe was inverted several times before being unscrewed and withdrawing 0.25 mL into a tuberculin syringe. 2.4. Safety assessments Subjects underwent a physical examination and had vital signs and body temperature evaluated at each visit. Hematology/clinical chemistry tests and urinalysis were conducted at Screening, Day 28, Day 56, and Month 7. Solicited adverse events (AEs) were recorded in subject diaries for 7 consecutive days after each vaccination, Day 0 being the day of first vaccination. Solicited AEs were: 1) Local: injection site swelling, itching, pain, induration redness, tenderness (i.e., pain upon touching) and 2) Systemic: irritability, nausea, vomiting, diarrhea, flu-like symptoms, excessive fatigue, muscle pain, rash, headache, fever, and loss of appetite. Solicited AEs were by definition considered to be related to the study vaccine. Severity was graded by the investigator using a modified version of the Division of AIDS (DAIDS) Table for Grading the Severity of Adult and Pediatric Adverse Events [15] as follows. Fever (tympanic): Grade 1 = 37.7–38.6 °C, Grade 2 = 38.7–39.3 °C, Grade 3 = 39.4–40.5 °C, Grade 4= > 40.5 °C. Measurable local reactions (redness, induration and swelling): Grade 1 = < 1 cm, Grade 2 = 1 to ≤3 cm, Grade 3 = > 3 cm and Grade 4 = necrosis. For other AEs, grading ranged from Grade 1 = generally describing non-limiting, minimal symptoms to Grade 4 = generally describing symptoms causing inability to perform usual activities or being life-threatening. Unsolicited AEs were recorded between Day 0 and Month 7 and severity assessments made using the DAIDS Table for Grading AEs.

2. Methods 2.1. Study population The study population included 100 healthy children and adolescents aged ≥2 months to < 18 years from non-endemic countries planning to travel to an area where JE was endemic and for whom JE vaccination was recommended. Subjects with a clinical history of any Flavivirus disease or vaccination against JE, yellow fever, West Nile virus or dengue were excluded. Exposure to JE was to be avoided until 1 week after the second dose of IXIARO®. Active or passive immunization within 1 week before and 1 week after each vaccination was not permissible. A history of tick-borne encephalitis (TBE) vaccination was allowed. 2.2. Study conduct

2.5. Immunogenicity assessment

The study was a single-arm, open-label Phase 3 study conducted in the United States of America (4 sites), Australia (2 sites), Denmark (1 site), Sweden (1 site) and Germany (3 sites). The study was conducted in two parts. All subjects were vaccinated i. m. on Days 0 and 28 (a 4-day time window was allowed for day 28 vaccination). For the first 64 enrolled subjects, referred to as ‘immunogenicity subgroup’, immunogenicity and safety were assessed at an in-person visit on Day 56; a final safety visit or phone call was performed at Month 7. To combat recruitment difficulties, the last 36 enrolled subjects were followed only for safety, while immunogenicity assessments on Day 56 were abandoned; that visit was then allowed to take place any time between 1 week and 2 months after the last vaccination, and the primary endpoint was changed from seroconversion rate to the rate of subjects with serious adverse events (SAEs) and medically-attended adverse events (AEs) up to Day 56 after the first vaccination. The study was conducted in accordance with the Declaration of Helsinki (2008). The subject's legal representative provided written informed consent. The subject's written assent was obtained if required

The immunogenicity endpoints were seroconversion rates (SCRs) and geometric mean titers (GMTs) for JEV neutralizing antibodies, assessed on Day 56 and Month 7. JEV neutralizing antibodies were measured using a validated plaque reduction neutralization test (PRNT) following the method described by Tauber et al. [16]. Seroconversion was defined as PRNT50 ≥ 10, i.e., a serum dilution of 1:10 or higher resulting in a 50% plaques number reduction. This is also the WHO accepted criterion for assuming seroprotection against JEV [17,18]. 2.6. Statistics As there was no hypothesis tested, no formal sample size calculation was performed. A convenience sample of 100 subjects was considered sufficient to bridge data from children in JEV-endemic countries to the population of traveling children from western countries, in light of a population that was very difficult to enrol for the study. Only descriptive statistics were performed. Analyses were stratified by age, which was derived as the number of years between the birth date and the date of first dose of vaccine administration. 2


T. Jelinek et al.

subject was calculated as 18 years at the time of first vaccination but in reality the subject was confirmed as less than 18 years old. The immunogenicity subgroup included 5 subjects aged ≥2 months to < 3 years, 15 subjects aged ≥3 years to < 12 years and 44 subjects aged ≥12 years to < 18 years.

2.7. Safety analyses Safety analyses included all subjects who received at least 1 vaccination. The number and percentage of subjects with any AE (solicited or unsolicited) up to Day 56 and up to Month 7 and exact 95% confidence intervals (CIs) for the rates were calculated. The primary endpoint was the rate of subjects with serious or medically attended AEs up to Day 56. For solicited AEs, percentages were based on subjects assessable for a given symptom. Fisher exact test was performed to compare the AE rates between groups. Medical Dictionary for Regulatory Activities was used for AE coding (version 13.0) and all analyses were run in SAS version 9.2 (SAS Institute Inc. Cary, NC, USA).

3.2. Overview of adverse events up to day 56 and month 7 Adverse events reported up to Day 56 and Month 7 are summarized by dose group in Table 2. In the 0.25 ml IXIARO® dose group, 83.3% of subjects (10/12) experienced at least one solicited or unsolicited AE up to Day 56 and 91.7% of subjects (11/12) experienced at least one solicited or unsolicited AE up to Month 7. For subjects who had received the 0.5 ml IXIARO® dose, 76.1% (67/88) and 80.7% (71/88) reported at least one AE up to Day 56 or Month 7, respectively.

2.8. Immunogenicity analyses Immunogenicity analyses were performed on the Intent-to-treat (ITT) population, defined as all subjects of the immunogenicity subgroup who received at least 1 vaccination. The number and percentage of subjects achieving seroconversion at Screening, Day 56, and Month 7 were calculated based on the number of subjects with immunogenicity data available, for each IXIARO® dose group, and for both dose groups combined, along with the 95% 2-sided CI for the percentages, calculated according to the methods of Altman [19]. GMTs were summarized at Screening, Day 56 and Month 7 by dose group. Geometric mean titers and 95% CIs were calculated by taking the anti-logs of the means and 95% CI of the log-transformed titers. Negative sera were assigned the value of 5 for calculation of GMT.

3.3. Solicited adverse events The overall percentage of subjects experiencing AEs within the first 7 days after the first or the second injection are depicted in Fig. 1A and B. The majority of solicited local and systemic AEs were mild (Grade 1), six Grade 2 and one Grade 3 reaction (headache) was observed. Serious and medically-attended adverse events (SAE and MAE). The rate of subjects experiencing any SAE or MAE up to Day 56 (primary endpoint) and Month 7 (secondary endpoint) after the first vaccination is presented in Table 2. Individual SAEs/MAEs are presented in Table 3. There were no SAEs in the 0.25 ml IXIARO® group. In the 0.5 ml IXIARO® group, no SAE occurred to Day 56 and 3.4% (3/88) subjects experienced an SAE between Day 56 and Month 7; these were type I diabetes mellitus, dizziness and intentional self-injury, in 1 out of 88 subjects (1.1%) each. Only dizziness reported at Month 4.5 after second vaccination was considered to be possibly related by the investigator, but due to the long interval between vaccination and event onset, it was considered unrelated by the sponsor. No deaths occurred in this study. Up to Day 56, 33.3% (4/12) of subjects from the 0.25 ml IXIARO® group and 9.1% (8/88) in the 0.5 ml dose group reported a MAE. The most common MAE in the 0.25 ml IXIARO® dose group was pyrexia, affecting 16.7% (2/12) of subjects. In the 0.5 ml group, nasopharyngitis affected two subjects (2/88, 2.3%) while all other MAEs were just reported once. For the 0.25 ml IXIARO® group no further MAEs were recorded until Month 7, while 8 additional subjects in the 0.5 ml IXIARO® dose group reported a MAE after Day 56. MAEs with an incidence of at least ≥2% are shown in Table 3.

3. Results 3.1. Subject disposition Between February 24th, 2010 and January 24th, 2013, 100 subjects were enrolled, 12 subjects in the 0.25 ml IXIARO® dose group, and 88 subjects in the 0.5 ml dose group. The immunogenicity subgroup comprised 64 (64.0%) subjects, 5/64 subjects (7.8%) in the 0.25 ml IXIARO® dose group and 59/64 (92.2%) subjects in the 0.5 ml dose group. All but 2 subjects (both in the 0.5 ml dose group) received their second IXIARO® injection. In total, 92 (92%) subjects completed the study up to Month 7. Eight subjects prematurely discontinued (withdrawal of consent, 1 subject/0.5 ml IXIARO®; lost to follow up, 2 subjects/0.25 ml IXIARO®; and 5 subjects/0.5 ml IXIARO®. Demographic data are summarized in Table 1. Gender distribution was balanced in treatment groups. 12 subjects were aged ≥2 months to < 3 years; 29 subjects were aged ≥3 years to < 12 years and 59 subjects were aged ≥12 years to < 18 years. In accordance with German law, birth dates were entered as 01/real month/real year. As a result, the age of 1

3.4. Unsolicited adverse events Unsolicited AEs recorded in at least 10% or more of the safety population are shown in Table 4. The proportion of subjects with unsolicited AEs was lower in the 0.5 ml IXIARO® dose groups compared to the 0.25 ml IXIARO® dose group at Day 56 (29.5% vs. 83.3%) and Month 7 (43.2% vs. 91.7%). As shown in Table 4, the only unsolicited AE with a frequency exceeding 10% up to Day 56 was pyrexia occurring in 25% of subjects (3/12) in the 0.25 ml dose group. In the 0.5 ml IXIARO® dose group, no unsolicited AEs had an incidence of ≥10%. Related unsolicited AEs are described in Table 4. All related unsolicited AEs were reported in no more than 1 subject per dose group.

Table 1 Demographic and baseline characteristics by dose group, safety population.

Age at Visit 1 (years) Mean (SD) Median (min, max) Sex Male Female Race Asian White Black of African heritage or African American Other

IXIARO 0.25 ml (N = 12) n (%)

IXIARO 0.5 ml (N = 88) n (%)

1.81 (0.811) 1.49 (0.9, 3.0)

12.96 (4.535) 15.19 (3.0, 18.0)

7 (58.3) 5 (41.7)

40 (45.5) 48 (54.5)

3 (25.0) 8 (66.7) 1 (8.3)

10 (11.4) 75 (85.2) 2 (2.3)

0

1 (1.1)

3.5. Immune response at day 56 and month 7 Secondary endpoints of this study were SCR and GMT at Day 56 and Month 7 after first IXIARO® injection. At Day 56, the SCR was 100% (data from 62 subjects at that visit) for the 0.25 ml IXIARO® and 0.5 ml IXIARO® dose groups, indicating protection against JEV in all subjects. At Month 7, the SCR was still at 91.2% (31/34) for both dose groups. Detailed immunogenicity assessments are summarized in Table 5. By

Abbreviations: SD, standard deviation. Note 1: Percentages are based on the number of subjects in the Safety Population.

3


T. Jelinek et al.

Table 2 Summary of all adverse events (solicited and unsolicited) up to day 56 and month 7 by dose group. IXIARO 0.25 ml

IXIARO 0.5 ml

IXIARO 0.25 ml

IXIARO 0.5 ml

n (%) [95% CI]

n (%) [95% CI]

n (%) [95% CI]

n (%) [95% CI]

Day 56 N Any AE Any related AE SAEs or MAEs Any SAE Any MAE Related SAEs

12 10 (83.3) [51.6, 97.9] 6 (50.0) [21.1, 78.9] 4 (33.3) [9.9, 65.1] 0 [0.0, 26.5] 4 (33.3) [9.9, 65.1] 0 [0.0, 26.5]

Month 7 88 67 (76.1) [65.9, 84.6] 62 (70.5) [59.8, 79.7] 8 (9.1) [4.0, 17.1] 0 [0.0, 4.1] 8 (9.1) [4.0, 17.1] 0 [0.0, 4.1]

12 11 (91.7) [61.5, 99.8] 6 (50.0) [21.1, 78.9] 4 (33.3) [9.9, 65.1] 0 [0.0, 26.5] 4 (33.3) [9.9, 65.1] 0 [0.0, 26.5]

88 71 (80.7) [70.9, 88.3] 63 (71.6) [61.0, 80.7] 16 (18.2) [10.8, 27.8] 3 (3.4) [0.7, 9.6] 16 (18.2) [10.8, 27.8] 1 (1.1) [0.0, 6.2]

Abbreviations: AE, adverse event; CI, confidence interval; n, number of subjects who experienced each event; N, number of subjects in the Safety Population in the indicated dose group; SAE, serious adverse event; MAE, medically–attended adverse event. Note 1: Percentages are based on the number of subjects in the treatment group in the safety population. The CI is an exact CI for a percentage. Note 2: Related AEs are those assessed as possibly or probably related to vaccination. Solicited AEs within 7 days after any injection were per definition considered related to the injection.

Fig. 1. Solicited local (A) and systemic (B) AEs Within 7 Days After Any Vaccination in Subjects Receiving IXIARO 0.25 ml or IXIARO 0.5 ml. The percentage of subjects who experienced a given symptom, all severity grades combined, is indicated above each bar. (A) No Grade 3 or Grade 4 events were reported for either dose group. For induration, swelling and redness, the severity grades were Grade 1 = < 1 cm, Grade 2 = 1 to ≤3 cm, Grade 3 = > 3 cm, Grade 4 = necrosis. For other symptoms gradings ranged from Grade 1 = generally describing non limiting, minimal symptoms to Grade 4 = generally describing symptoms causing inability to perform basic self-care or leading to hospitalisations. Severity was not assessable for all subjects. * indicates statistically significant difference (p < 0.05) between treatment groups (Fisher's exact test). (B) No Grade 2 or Grade 3 events were reported for the IC51 0.25 ml dose group. One Grade 3 headache was reported in the IC51 0.5 ml dose group. No Grade 4 events were reported for either dose group. Fever grading: Grade 1 = 37.7–38.6 °C, Grade 2 = 38.7–39.3 °C, Grade 3 = 39.4–40.5 °C, and Grade 4 = > 40.5 °C. For other AEs, gradings ranged from Grade 1 = generally describing non-limiting, minimal symptoms to Grade 4 = generally describing symptoms causing inability to perform usual activities, leading to hospitalisations or being life threatening. Severity was not assessable for all subjects. *indicates statistically significant difference (p < 0.05) between dose groups (Fisher's exact test).

4


T. Jelinek et al.

Table 3 Serious adverse events and medically-attended adverse events up to day 56 and month 7. MedDRA preferred term

IXIARO 0.25 ml

IXIARO 0.5 ml

IXIARO 0.25 ml

IXIARO 0.5 ml

n (%) [95% CI]

n (%) [95% CI]

n (%) [95% CI]

n (%) [95% CI]

Day 56 N 12 MAEs with an incidence of ≥ 2% in at least 1 group Nasopharyngitis 1 (8.3) [0.2, 38.5] Bronchitis 1 (8.3) [0.2, 38.5] Diarrhea 1 (8.3) [0.2, 38.5] Haematochezia 1 (8.3) [0.2, 38.5] Nausea 1 (8.3) [0.2, 38.5] Upper abdominal pain 0 Vomiting 0 [0.0, 26.5] Pyrexia 2 (16.7) [2.1, 48.4] Cough 1 (8.3) [0.2, 38.5]

Month 7 88

12

88

2 0 0 0 0 0 1 1 0

1 1 1 1 1 0 0 2 1

2 0 0 0 1 2 3 2 0

(2.3) [0.3, 8.0] [0.0, 4.1] [0.0, 4.1] [0.0, 4.1] [0.0, 4.1] (1.1) [0.0, 6.2] (1.1) [0.0, 6.2] [0.0, 4.1]

(8.3) [0.2, 38.5] (8.3) [0.2, 38.5] (8.3) [0.2, 38.5] (8.3) [0.2, 38.5] (8.3) [0.2, 38.5] [0.0, 26.5] [0.0, 26.5] (16.7) [2.1, 48.4] (8.3) [0.2, 38.5]

(2.3) [0.3, [0.0, 4.1] [0.0, 4.1] [0.0, 4.1] (1.1) [0.0, (2.3) [0.3, (3.4) [0.7, (2.3) [0.3, [0.0, 4.1]

8.0]

6.2] 8.0] 9.6] 8.0]

Abbreviations: AE, adverse event; CI, confidence interval; n, number of subjects who experienced each event; N, number of subjects in the Safety Population in the indicated dose group; SAE, serious adverse event; MAE, medically–attended adverse event. Note 1: Percentages are based on the number of subjects in the corresponding dose group. The CI is an exact CI for a percentage.

age group, GMTs in the 0.5 ml dose group were 508 in the ≥3 to < 12 years group and 295 in the ≥12 to < 18 years group at Day 56. Of note, 50 subjects out of 62 with baseline results traveled to a JE endemic area and 12 subjects did not. The SCR at month 7 was similar between subjects who had traveled (91.7% SCR) and those who had not (SCR 90%). In addition, the overall GMT at Month 7 for those who traveled was 51 and was similar to those who had not traveled, 74.

headache in 7.4% of subjects, again similar as seen with adults with headache (28%) and muscle pain (15.6%) being most common. The majority of solicited AEs were mild, which is in line with data from other studies with IXIARO® in both adults [20] and children [12]. Adverse events considered possibly or probably related to the vaccine by the investigator were noted in 69% of subjects, a rate that is higher compared to that reported in adults (approximately 40%) [21]. Notably, the assessments of safety in the pediatric trials for IXIARO® differed from the methods employed during the studies in adults in that solicited AEs were always considered to be causally associated with vaccination (i.e., related) in the pediatric trials. This difference in collecting safety data is considered to have affected the rate of subjects with related AEs. The proportion of subjects with unsolicited AEs considered related to vaccine by study investigators was low at just 6% of subjects and included one subject (0.25 ml group) with rash and pruritus eight days after the first dose, and one subject each with the following symptoms: cough and sore throat 2 days after the first vaccination, irritability 7 days after first vaccination, eczema and ear canal erythema 1 month after first vaccination, upper respiratory tract infection 2 months after vaccination, and dizziness 5 months after vaccination.

4. Discussion The present study was an uncontrolled, open‐label Phase 3 study to assess safety as well as immunogenicity (in a subgroup of subjects) of IXIARO® in children aged ≥ 2 months to < 18 years planning to travel to countries where JE is endemic. The overall AE profile in this primarily adolescent study population was comparable with that in adults for rates of solicited local and systemic AEs; lower rates were observed for unsolicited AEs. The most frequently reported local AEs were injection site tenderness in 45% of subjects and injection site pain in 23.7% of subjects. These reactions are also the ones most commonly seen in adults [20]. The most common systemic AEs were muscle pain in 29.3%, excessive fatigue in 10%, and

Table 4 Common unsolicited adverse events and related unsolicited adverse events up to day 56 and month 7. MedDRA preferred term

IXIARO 0.25 ml

IXIARO 0.5 ml

IXIARO 0.25 ml

IXIARO 0.5 ml

n (%) [95% CI]

n (%) [95% CI]

n (%) [95% CI]

n (%) [95% CI]

Day 56 N 12 Unsolicited AEs with an incidence of ≥ 10% in at least 1 group Nasopharyngitis 0 Cough 0 Pyrexia 3 (25.0) [5.5, 57.2] Lymphadenopathy 0 Related unsolicited AEs Upper respiratory tract infection 0 Dizziness 0 Cough 0 [0.0, 26.5] Oropharyngeal pain 0 [0.0, 26.5] Eczema 0 [0.0, 26.5] Pruritus 1 (8.3) [0.2, 38.5] Rash erythematous 1 (8.3) [0.2, 38.5] Ear canal erythema 0 [0.0, 26.5] Irritability 0 [0.0, 26.5]

Month 7 88

12

0 0 1 (1.1) [0.0, 6.2] 0

4 2 3 2

(33.3) (16.7) (25.0) (16.7)

0 0 1 1 1 0 0 1 1

0 0 0 0 0 1 1 0 0

[0.0, 26.5] [0.0, 26.5] [0.0, 26.5] [0.0, 26.5] [0.0, 26.5] (8.3) [0.2, 38.5] (8.3) [0.2, 38.5] [0.0, 26.5] [0.0, 26.5]

(1.1) [0.0, (1.1) [0.0, (1.1) [0.0, (0.0, 4.1) (0.0, 4.1) (1.1) [0.0, (1.1) [0.0,

6.2] 6.2] 6.2]

6.2] 6.2]

88 [9.9, [2.1, [5.5, [2.1,

65.1] 48.4] 57.2] 48.4]

4 4 3 3

(4.5) (4.5) (3.4) (3.4)

[1.3, [1.3, [0.7, [0.7,

1 1 1 1 1 0 0 1 1

(1.1) [0.0, (1.1) [0.0, (1.1) [0.0, (1.1) [0.0, (1.1) [0.0, (0.0, 4.1) (0.0, 4.1) (1.1) [0.0, (1.1) [0.0,

11.2] 11.2] 9.6] 9.6] 6.2] 6.2] 6.2] 6.2] 6.2]

6.2] 6.2]

Abbreviations: AE, adverse event; CI, confidence interval; n, number of subjects who experienced each event; N, number of subjects in the Safety Population in the indicated dose group. Note 1: Percentages are based on the number of subjects in the safety populations in a given dose group. The CI is an exact CI for a percentage.

5


T. Jelinek et al.

At Month 7, 91.2% of the subjects remained above the threshold of protection of 10. GMTs at Month 7 were 48 and 57 in the 0.25 ml and 0.5 ml groups, respectively. In conclusion, IXIARO® was highly immunogenic in both dose groups and while long-term data are limited, titers remained at protective levels in > 90% of subjects up to Month 7. In longer-term follow-up studies that have since been conducted, it became apparent that protective titers are maintained in around 80% of subjects for up to three years after the primary series. While most of these data were generated in JE endemic areas where natural boosting might influence the persistence of antibodies, a booster dose after 12 months generated a strong anamnestic response and elevated the protection rate to 100% for a further 24 months [25]. Based on those data, a booster in children is currently recommended to be administered after 12 months in the European label for IXIARO®, further regulatory filings are pending [10]. Several limitations may affect interpretation of the results. First, this was an open label and uncontrolled study design. The reason for choosing this methodologically limited design for a Phase 3 study was the expected (and observed) difficulty in recruiting subjects for this study – recruiting another 100 subjects into a control group would have substantially delayed time to pediatric licensure for the vaccine, at a time when no pediatric JE vaccine was available. Second, the number of subjects overall and in particular in the 0.25 ml group was low. Again, this is owed to practical considerations as the age group below 3 years was the most difficult to recruit. These limitations may weaken conclusions regarding the safety or immunogenicity. E.g., the sample size was too low to allow detection of rare adverse events in this study. In addition, a meaningful comparison between the two dose groups is impossible. However, another pediatric phase III study with IXIARO® was conducted in the Philippines and included a significantly higher number of children (N = 1869). In that study, subjects receiving JE vaccine had similar rates of unsolicited AEs within each age group compared to control vaccines (Prevnar® or Havrix®). Rates for unsolicited AEs were also clearly associated with age group rather than dose group, and were highest in subjects younger than 3 years [13]. Three subjects in the present study reported previous TBE vaccinations. Hence, even though prior immunization against the tick borne encephalitis (TBE) virus has been shown to be associated with a better immune response to IXIARO® [26], this was not considered a significant confounding factor in this study due to limited number. Similarly, natural exposure to JEV seems not to have occurred in this study. Although 50 subjects traveled to a JE endemic area, the overall GMT as well as SCR at month 7 were similar to those who had not traveled. In conclusion, IXIARO® was generally well tolerated in both dose groups, with an overall AE profile confirming the favorable safety profile seen in a larger study in an endemic country. IXIARO® was highly immunogenic in both dose groups. While long-term data are limited, titers remained at protective levels in > 90% of subjects up to month 7.

Table 5 Seroconversion rates and geometric mean titers by dose group, ITT population. IXIARO 0.25 ml Baseline (Visit 0) Seroconversion rate N 5 n (%) 0 95% CI 0.0; 43.4 Geometric mean titers, value Geometric mean 5.00 95% CI for geometric 5.00; 5.00 mean Median (min, max) 5.00 (5.0, 5.0) Day 56 (Visit 3) Seroconversion rate N 5 n (%) 5 (100.0) 95% CI 56.6; 100.0 Geometric mean titers, value Geometric mean 216.18 95% CI for geometric 105.97; 441.00 mean Median (min, max) 259.00 (102.0, 457.0) Month 7 (Visit 4) Seroconversion rate N 2 n (%) 2 (100.0) 95% CI 34.2; 100.0 Geometric mean titers, value Geometric mean 47.96 95% CI for geometric 0.00; 3214485.72 mean Median (min, max) 47.96 (20.0, 115.0)

IXIARO 0.5 ml

Total

59 0 0.0; 6.1

64 0 0.0; 5.7

5.00 5.00; 5.00

5.00 5.00; 5.00

5.00 (5.0, 5.0)

5.00 (5.0, 5.0)

57 57 (100.0) 93.7; 100.0

62 62 (100.0) 94.2; 100.0

340.74 269.83; 430.28

328.46 263.73; 409.09

313.00 (56.0, 7380.0)

309.99 (56.0, 7380.0)

32 29 (90.6) 75.8; 96.8

34 31 (91.2) 77.0; 97.0

57.12 38.41; 84.94

56.53 38.66; 82.67

90.95 (5.0, 275.0)

90.95 (5.0, 275.0)

Abbreviations: CI, confidence interval; ITT, Intent-to-treat; N, number of subjects with data at current visit; n, number of subjects achieving seroconversion; SD, standard deviation. Note 1: Seroconversion was defined as a PRNT50 titer ≥1:10. Note 2: Percentages are based on the number of subjects in the ITT population with nonmissing titers at Visit 0 and current visit.

The primary endpoint of this study was the rate of subjects who experienced SAEs or MAEs up to Day 56 after first IXIARO® injection. No SAEs occurred up to that day in either dose group. This is in line with results of IXIARO studies conducted both in adults (1% with SAEs) [20], and in children from endemic areas (approx. 0.5% with SAEs) [13], and not surprising given the limited sample size and general paucity of SAEs in healthy volunteer vaccine trials. Overall, the data support the excellent safety profile of the vaccine also in children who have not been pre-exposed to Japanese encephalitis virus (i.e. traveling children). Safety has historically been an important element for recommending vaccination against Japanese encephalitis in travelers, as recommendations aimed on minimizing exposure to a mouse-brain-derived vaccine with a worrisome safety profile, contrasted to a relatively low risk of acquiring Japanese encephalitis itself during travel [22]. With availability of encouraging safety data in children [13] and adults [20] for this modern Vero cell culture produced JE vaccine it may be appropriate to reconsider the benefit-risk considerations and incorporate a more liberal attitude towards JE vaccination in travelers. JE continues to be a changing and unpredictable threat for travelers while a safe vaccine is now available [23] for adults and children from 2 months old. In the assessment of immunogenicity, at Day 56 after either 0.25 ml or 0.5 ml IXIARO®, all subjects (SCR 100%) had antibody titers that met the criteria accepted as protective titer by WHO [17,18]. GMTs at Day 56 were 216 and 341 in the IXIARO® 0.25 ml and IXIARO® 0.5 ml groups, respectively, which were slightly higher compared to GMTs in adults ranging from 190 to 240 observed with the 2-dose regimen [16,21,24].

Sources of funding This work was supported by Valneva Austria GmbH. Declaration of interests SK, VK, SE-L, KD, CT are employees of Valneva SE or its affiliates, the manufacturer of IXIARO®. TJ received speaker fees from Valneva SE. Authors contribution VK, SE-L, KD, CT developed the study protocol. MAC, JPC, TJ, DJM, KL, AWG, EDB, SHFH, HHA accrued subjects and data. SK provided serological data. VK, SE-L, KD analyzed the statistical data. CT drafted the manuscript. All authors reviewed the manuscript. 6


T. Jelinek et al.

Acknowledgements

[12] Kaltenbock A, Dubischar-Kastner K, Schuller E, Datla M, Klade CS, Kishore TS. Immunogenicity and safety of IXIARO (IC51) in a Phase II study in healthy Indian children between 1 and 3 years of age. Vaccine 2010;28(3):834–9. [13] Dubischar KL, Kadlecek V, Sablan Jr. B, Borja-Tabora CF, Gatchalian S, EderLingelbach S, et al. Safety of the inactivated Japanese encephalitis virus vaccine IXIARO in children: an open-label, randomized, active-controlled, phase 3 study. Pediatr Infect Dis J 2017;36(9):889–97. [14] Dubischar KL, Kadlecek V, Sablan JB, Borja-Tabora CF, Gatchalian S, EderLingelbach S, et al. Immunogenicity of the inactivated Japanese encephalitis virus vaccine IXIARO in children from a Japanese encephalitis virus-endemic region. Pediatr Infect Dis J 2017;36(9):898–904. [15] National Institute of Allergy and Infectious Diseases. Division of AIDS, table for grading the severity of adult and pediatric adverse events. Version 1.0. 2004. [December]. [16] Tauber E, Kollaritsch H, Korinek M, Rendi-Wagner P, Jilma B, Firbas C, et al. Safety and immunogenicity of a Vero-cell-derived, inactivated Japanese encephalitis vaccine: a non-inferiority, phase III, randomised controlled trial. Lancet 2007;370(9602):1847–53. [17] Hombach J, Solomon T, Kurane I, Jacobson J, Wood D. Report on a WHO consultation on immunological endpoints for evaluation of new Japanese encephalitis vaccines, WHO, Geneva, 2-3 September, 2004. Vaccine 2005;23(45):5205–11. [18] Hombach J, Barrett AD, Cardosa MJ, Deubel V, Guzman M, Kurane I, et al. Review on flavivirus vaccine development. Proceedings of a meeting jointly organised by the World Health organization and the Thai ministry of public Health, 26-27 april 2004, Bangkok, Thailand. Vaccine, vol. 23. 2005. p. 2689–95. 21. [19] Altman DG, Machin D, Bryant TN, Gardner MJ. Statistics with confidence. BMJ. second ed.2000. [20] Dubischar-Kastner K, Kaltenboeck A, Klingler A, Jilma B, Schuller E. Safety analysis of a Vero-cell culture derived Japanese encephalitis vaccine, IXIARO (IC51), in 6 months of follow-up. Vaccine 2010;28(39):6463–9. [21] Tauber E, Kollaritsch H, von Sonnenburg F, Lademann M, Jilma B, Firbas C, et al. Randomized, double-blind, placebo-controlled phase 3 trial of the safety and tolerability of IC51, an inactivated Japanese encephalitis vaccine. J Infect Dis 2008;198(4):493–9. [22] Wilder-Smith A, Halstead SB. Japanese encephalitis: update on vaccines and vaccine recommendations. Curr Opin Infect Dis 2010;23(5):426–31. [23] Connor B, Bunn WB. The changing epidemiology of Japanese encephalitis and New data: the implications for New recommendations for Japanese encephalitis vaccine. Tropical diseases, travel medicine and vaccines 2017;3:14. [24] Kaltenbock A, Dubischar-Kastner K, Eder G, Jilg W, Klade C, Kollaritsch H, et al. Safety and immunogenicity of concomitant vaccination with the cell-culture based Japanese Encephalitis vaccine IC51 and the hepatitis A vaccine HAVRIX1440 in healthy subjects: a single-blind, randomized, controlled Phase 3 study. Vaccine 2009;27(33):4483–9. [25] Dubischar-Kastner K, Sablan BJ. Antibody persistence in children from JE non-endemic and JE endemic countries and after a booster dose of inactivated Japanese encephalitis vaccine. Abstract FC2.04. Conference of the international society of travel medicine. 2015. Quebec, Canada. [26] Cramer JP, Dubischar K, Eder S, Burchard GD, Jelinek T, Jilma B, et al. Immunogenicity and safety of the inactivated Japanese encephalitis vaccine IXIARO (R) in elderly subjects: open-label, uncontrolled, multi-center, phase 4 study. Vaccine 2016;34(38):4579–85.

We are grateful to the following individuals for their valuable contributions at various stages of this trial: All clinical study participants, Kerstin Westritschnig, Christoph Klade, Vera Buerger for contributions during the study planning phase, Evelyn Hatzenbichler, Astrid Kaltenboeck for contributions during study setup and conduct, Martin Spruth for development of the serological assay (all formerly Intercell AG, Vienna, Austria). Stefan Hagmann was affiliated with Bronx - Lebanon Hospital Center, Division of Pediatric Infectious Diseases, New York, NY, U.S. when this study was conducted and is currently affiliated with Division of Pediatric Infectious Disease, Steven and Alexandra Cohen Children's Medical Center of New York, New Hyde Park and Donald and Barbara Zucker School of Medicine at Hofstra/Northwell Health, Hempstead, NY, USA. References [1] Solomon T, Dung NM, Kneen R, Gainsborough M, Vaughn DW, Khanh VT. Japanese encephalitis. J Neurol Neurosurg Psychiatry 2000;68(4):405–15. [2] Campbell GL, Hills SL, Fischer M, Jacobson JA, Hoke CH, Hombach JM, et al. Estimated global incidence of Japanese encephalitis: a systematic review. Bull World Health Organ 2011;89(10):766–74. 74A-74E. [3] Solomon T, Kneen R, Dung NM, Khanh VC, Thuy TT, Ha DQ, et al. Poliomyelitis-like illness due to Japanese encephalitis virus. Lancet 1998;351(9109):1094–7. [4] Mathers CD, Ezzati M, Lopez AD. Measuring the burden of neglected tropical diseases: the global burden of disease framework. PLoS Neglected Trop Dis 2007;1(2). e114. [5] Update on Japanese encephalitis vaccine for children: United States, May 2011. MMWR Morbidity and mortality weekly report. 2011;60(20):664–5. [6] Haemophilus influenzae type b (Hib) Vaccination Position Paper - July 2013. Releve epidemiologique hebdomadaire. 2013;88(39):413–26. [7] Fischer M, Lindsey N, Staples JE, Hills S. Japanese encephalitis vaccines: recommendations of the advisory committee on immunization practices (ACIP). MMWR recommendations and reports. MMWR Recomm Rep (Morb Mortal Wkly Rep) 2010;59(RR-1):1–27. [8] Hills SL, Griggs AC, Fischer M. Japanese encephalitis in travelers from non-endemic countries, 1973-2008. Am J Trop Med Hyg 2010;82(5):930–6. [9] Halstead SB, Jacobson J, Dubischar-Kastner K. Japanese encephaltis vaccines. In: Plotkin S, OWOffit P, editors. Vaccines. sixth ed.Elsevier; 2012. p. 201–5. [10] European Medicines Agency IXIARO. Summary of Product Characterisctics. http:// www.ema.europa.eu/ema/index.jsp?curl=pages/medicines/human/medicines/ 000963/human_med_000862.jsp&mid=WC0b01ac058001d124; 2009, Accessed date: 14 February 2018. [11] U.S Food and Drug administration IXIARO. Prescribing Information. https://www. fda.gov/downloads/biologicsbloodvaccines/vaccines/approvedproducts/ ucm142569.pdf; 2015, Accessed date: 14 February 2018.

7