ABSTRACT
The Ad26.RSV.preF/RSV preF protein vaccine has previously demonstrated efficacyin protecting older adults against respiratory syncytial virus (RSV)–related lower respiratory tract disease in a phase 2b study. This study compared the immunogenicity of vaccine clinical trial material (CTM) representative of phase 2b clinical studies with CTM used in phase 3 clinical studies. A total of 248 adults aged 60–75 years, randomized in a 1:1 ratio, received one dose of either phase 3 CTM or phase 2b CTM. Solicited adverse events (AEs), unsolicited AEs, and serious AEs (SAEs) were assessed for 7-d, 28-d, and 6-month periods post-vaccination, respectively. RSV preF-ELISA antibody titers and RSV neutralizing titers were measured before and 14 d after vaccination. The phase 3 CTM-induced preF-ELISA response at Day 15, in terms of geometric mean titer, was shown to be non-inferior to that induced by phase 2b CTM. The RSV neutralizing antibody titers were also similar in the two groups at Day 15. The safety profile in terms of solicited AEs, unsolicited AEs, or SAEs was in general similar between the phase 3 CTM and phase 2b CTM groups, and solicited AEs were mostly mild to moderate in intensity. No related SAEs were reported, and no safety concerns were identified.
KEYWORDS: Respiratory syncytial virus; RSV; vaccine; Ad26, immunogenicity, Ad26.RSV.preF, RSV preF protein
Introduction
The respiratory syncytial virus (RSV) is an important cause of severe respiratory disease in adults aged 60 y and above, especially in people with underlying chronic comorbidities, such as respiratory or cardiac conditions1 or with immunosuppression.2 In these populations, RSV infection can lead to life-threatening complications such as pneumonia or exacerbation of underlying conditions.3 Two recent meta-analyses estimated that yearly, 6.7 per 1000 adults ≥65 y of age, worldwide, had RSV-related acute respiratory infection (ARI)4 and 16.2 per 1000 adults ≥60 y of age, in high-income countries, had RSV ARI,5 with hospitalization rates of 1 per 10003 and 1.5 per 1000,5 respectively. Two vaccines have recently become available for the prevention of lower respiratory tract disease (LRTD) caused by RSV in individuals 60 y of age and older,6,7 both based on the RSV preF protein, i.e., the RSV F protein stabilized in its pre-fusion conformation.
The Ad26.RSV.preF/RSV preF protein vaccine, an alternative approach composed of the adenovirus type 26 (Ad26) vector expressing the preF protein combined with the preF protein, was shown immunogenic in older adults8 and efficacious in protecting against LRTD caused by RSV in a phase 2b study.9
Changes in the manufacturing process of the vaccine had occurred between the conduct of phase 2 and the start of phase 3 evaluation. This study was therefore undertaken, in adults aged 60–75 y, to compare the immunogenicity of clinical trial material (CTM) of the Ad26.RSV.preF/RSV preF protein vaccine evaluated in phase 3 clinical trials and representative of the intended commercial process with CTM representative of that evaluated in a phase 2b efficacy study.
Participants and methods
Participants and study design
This randomized, double-blind phase 3 study was conducted from October 2021 to September 2022 at 9 sites in the United States. Adults 60–75 y of age, in stable health, were randomly assigned, in a 1:1 ratio, to 2 groups to receive phase 3 CTM or phase 2b CTM of the Ad26.RSV.preF/RSV preF vaccine.
Participants provided written informed consent before participation in the study and before any study procedure was performed. Clinical procedures were approved by the ethical committees of the study centers and complied with good clinical practice principles, in accordance with the Declaration of Helsinki.10 The trial was registered at ClinicalTrials.gov (NCT05083585).
The primary objective of the trial was to demonstrate the non-inferiority of the phase 3 CTM to the phase 2b CTM in terms of immune response, as measured by preF ELISA, 14 d after vaccination. RSV neutralizing antibody response and the reactogenicity and safety of vaccines were assessed as secondary objectives.
Study vaccine
The study vaccine was made of two components: Ad26.RSV.preF (a recombinant, replication-incompetent Ad26 vector encoding the RSV preF protein) and recombinant RSV preF protein. These were mixed prior to administration as a single injection (1.0 mL) in the deltoid muscle. The Ad26.RSV.preF content was 1.0 × 1011 viral particles, and the preF protein content was 150 μg.
The manufacturing process of the vaccine was modified during the development of the vaccine; changes for the two components involved the use of new manufacturing sites and an increase in scale for all production steps. The phase 2b vaccine was manufactured according to the previous process, and the phase 3 vaccine lot was manufactured according to the changed process. Phase 3 lots manufactured according to the changed process were administered and assessed in studies NCT03982199, NCT05101486, NCT05071313, and NCT05070546.
Safety assessment
Adverse events (AEs), vital signs, and any abnormal physical examination findings were documented. Solicited and unsolicited AEs were recorded for 7 and 28 d after vaccination, respectively. The use of analgesic/antipyretic medication was recorded for 7 d post-vaccination. Serious AEs (SAEs) and potential AEs of specific interest (AESIs) were collected for 6 months after study vaccination. AEs were graded using an adapted US Food and Drug Administration Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials.11
Thrombosis and thrombocytopenia syndrome (TTS), also known as vaccine-induced immune thrombotic thrombocytopenia (VITT), has been observed following vaccination with the Janssen COVID-19 vaccine (Ad26.COV2.S). Ad26.RSV.preF utilizes the same non-replicative Ad26 vector as the Ad26.COV2.S vaccine but with a different transgene insert encoding the RSV preF protein. To capture any potential safety signal with the Ad26.RSV.preF/RSV preF protein vaccine in this study and other phase 3 studies, any thrombotic event and/or thrombocytopenia were considered as potential AESIs. Cases with concurrent thrombocytopenia and thrombosis, and cases of thrombosis with special characteristics, were considered as “qualified for assessment” and were to be further classified by level of certainty for TTS by an adjudication committee, composed of internal and external experts, according to case definitions from the Brighton Collaboration,12 the Centers for Disease Control and Prevention13 and the Pharmacovigilance Risk Assessment Committee, which is based on the proposal from National Institute for Health and Care Excellence.14 The adjudication committee also assessed cases for relatedness to the vaccine.
Immunogenicity analyses
Venous blood samples were collected for assessment of humoral immune responses on Day 1 and Day 15. Vaccine-elicited RSV A preF–specific immunoglobulin G (IgG) titers were measured using a validated enzyme-linked immunosorbent assay (ELISA). The lower limit of quantification for this assay was 3.4 EU/L. Titers of RSV A2-specific neutralizing antibodies were analyzed as a secondary endpoint. These assays were performed as described earlier.9
Statistical analyses
The sample size was defined to have 90% power to demonstrate non-inferiority as per the primary objective, which required a total of 105 evaluable participants per group.
The primary population for immunogenicity analyses was the Per-Protocol Immunogenicity Set at final analysis, which consisted of all vaccinated participants with post-vaccination immunogenicity data available, excluding participants with major protocol deviations expected to impact immunogenicity outcomes and samples collected out of the window.
Geometric mean preF-ELISA antibody titers and RSV-specific neutralizing antibody titers were calculated per group with 95% confidence intervals (CIs). The primary immunogenicity objective was assessed by calculating the 2-sided 95% CIs for the difference in log2-transformed Day 15 RSV preF-ELISA concentrations. The CIs were calculated via an analysis of variance, including both groups with log2-transformed Day 15 RSV preF-ELISA antibody titers as dependent variables and group as independent variables. The CIs around the difference were back-transformed to CIs around a geometric mean ratio (GMR; geometric mean titer [GMT] phase 3 CTM/GMT phase 2b CTM). The significance level (α) was 5% (2-sided). Non-inferiority was demonstrated if the 2-sided 95% CI for the GMR was entirely above 0.67. Secondary immunogenicity endpoints were analyzed descriptively.
The primary population for safety analyses consisted of all vaccinated participants (Full Analysis Set) with safety data available after vaccine administration. Safety analyses were descriptive; the number and percentage of participants with at least one AE were tabulated.
Results
Demographics
A total of 248 adults 60–75 y of age were randomized and vaccinated: 123 received the phase 3 CTM and 125 received the phase 2b CTM (Figure 1). The demographic characteristics were generally well balanced across groups (Table 1). Most participants were White (88.7%), and 51.6% of the participants were female. The median age was 63.0 y (ranging from 60 to 75 y).
Figure 1.
Participants’ disposition in the trial.
Table 1.
Summary of demographic and baseline characteristics – Full Analysis Set.
| Phase 3 CTM | Phase 2b CTM | |
|---|---|---|
| N | 123 | 125 |
| Age (years), mean (SD) | 63.8 (3.85) | 64.2 (4.34) |
| Female (%) | 65 (52.8%) | 63 (50.4%) |
| Male (%) | 58 (47.2%) | 62 (49.6%) |
| Height (cm), mean (SD) | 168.3 (10.52) | 168.1 (10.15) |
| Weight (kg), mean (SD) | 87.03 (21.463) | 84.43 (18.976) |
| BMI (kg/m2), mean (SD) | 30.56 (6.429) | 29.84 (6.117) |
| Risk level | ||
| Increased risk | 30 (27.5%) | 25 (22.7%) |
| Non-increased risk | 79 (72.5%) | 85 (77.3%) |
| Race, n (%) | ||
| Asian | 1 (0.8%) | 0 |
| Black or African American | 13 (10.6%) | 13 (10.4%) |
| White | 109 (88.6%) | 111 (88.8%) |
| Multiple | 0 | 1 (0.8%) |
| Ethnicity, n (%) | ||
| Hispanic or Latino | 45 (36.6%) | 58 (46.4%) |
| Not Hispanic or Latino | 78 (63.4%) | 65 (52.0%) |
| Not reported | 0 | 1 (0.8%) |
| Unknown | 0 | 1 (0.8%) |
CTM, clinical trial material.
Immunogenicity results
Baseline preF-ELISA and RSV neutralizing antibody titers were similar in the two groups. On Day 15, the preF-ELISA antibody GMTs and fold increases from baseline were similar in the 2 groups (Figure 2). The phase 3 CTM was shown non-inferior to the phase 2b CTM since the GMR for preF-ELISA antibody titers (phase 3 CTM versus phase 2b CTM) was 1.05, with a corresponding lower limit of the 2-sided 95% CI of 0.87, which was above the predefined 0.67 non-inferiority limit (Figure 3).
Figure 2.
PreF A IgG serum antibody response (ELISA) and titers of neutralizing antibodies to RSV A2 strain – Per-Protocol Immunogenicity Set.
N = number of participants with data; GMI = geometric mean increase. GMTs with 95% CIs shown in the figure; geometric mean values are expressed in EU/L for preF A IgG and in IC50 titers for neutralizing antibodies to RSV A2 strain. Ab, antibody; CTM, clinical trial material; ELISA, enzyme-linked immunosorbent assay; GMT, geometric mean titer; IC50, half-maximal inhibitory concentration; IgG, immunoglobulin G; RSV, respiratory syncytial virus.
Figure 3.
RSV preF A IgG serum antibody response and assessment of non-inferiority – Per-Protocol Immunogenicity Set.
Least squares (LS) means and corresponding CIs of the log2-transformed titers, back-transformed (by exponentiation: 2^lsmean) to a GMT.
RSV neutralizing antibody GMTs and fold increases from baseline at Day 15 were also similar in the two groups (Figure 2). The GMR for neutralizing antibody titers (phase 3 CTM versus phase 2b CTM) was 1.06 (95% CI: 0.86; 1.32), which was similar to the GMR calculated for preF-ELISA antibodies.
Safety results
The most frequently reported solicited local AE was pain/tenderness, which was reported by 66.9% and 57.6% of participants in the phase 3 CTM and phase 2b CTM groups, respectively (Figure 4). There was only one report of a Grade 3 solicited local AE: Grade 3 pain/tenderness for one participant in the phase 3 CTM group. The most frequently reported solicited systemic AE was fatigue, followed by headache and myalgia (Figure 4). These were also the most frequently reported Grade 3 solicited systemic AEs: reported by 1.6% to 6.4% of the participants in any group. Most solicited local and systemic AEs were Grade 1 or 2 in severity, and all were transient in nature. The median time to onset of solicited local AEs ranged from 1 to 2 d in the phase 3 CTM group and was 1 d in the phase 2b CTM group. The median duration of solicited local AEs ranged from 2 to 3 d in the phase 3 CTM group and from 2 to 5 d in the phase 2b CTM group.
Figure 4.
Frequency of solicited local and systemic adverse events after vaccination – Full Analysis Set.
Unsolicited AEs were reported by 7.3% of the participants in the phase 3 CTM group and by 9.6% of the participants in the phase 2b CTM group. Unsolicited Grade 3 AEs were reported by 1.6% of the participants in each group. Unsolicited AEs considered related to study vaccine by the investigator were reported by 5 (4.1%) participants in the phase 3 CTM group and in 4 (3.2%) participants in the phase 2b CTM group. These were chills, swelling, swelling face, vomiting, swollen tongue, pain in extremity, cough, respiratory tract congestion, and hyperhidrosis. No participants discontinued the study due to an unsolicited AE.
Two deaths were reported during the study: one cardiac arrest in the phase 3 CTM group and one cardiorespiratory arrest in the phase 2b CTM group. These were not considered related to study vaccine by the investigator. SAEs were reported by two participants (1.6%) in the phase 3 CTM and by 3 participants (2.4%) in the phase 2b CTM group. None of the SAEs was considered related to the study vaccine by the investigator.
During the study, deep vein thrombosis, which qualified as a potential AESI, was reported in one participant in the phase 3 CTM group on Day 154. The event was reported as an SAE, was Grade 2 in severity, was not considered related to the study vaccine by the investigator, and was resolved within 11 d. Given the absence of concurrent thrombocytopenia, since the participant had a normal platelet count, the event did not qualify for further assessment by the TTS adjudication committee. There were no cases of vaccine-induced TTS in this study.
Discussion
The primary objective of the trial was met, demonstrating the noninferiority of the vaccine phase 3 CTM to the vaccine phase 2b CTM in terms of the induced preF-ELISA antibody response measured 14 d after vaccination. The analytical comparability of vaccine lots manufactured before process changes and after process changes that were implemented was assessed for the two vaccine components in a dedicated analytical study. The pre-change and post-change RSV preF protein drug substance and drug product were considered comparable based on assessments of the in-process, release, characterization, stability, and degradation rate results. The Ad26.RSV.preF lots manufactured according to the two manufacturing processes were also shown to be comparable. Of note, the virus particle titers and infectious unit titers at release were slightly higher for the post-change lots. The lots were considered comparable in terms of virus particle/infectivity ratio.
The two Ad26.RSV.preF/preF protein vaccine CTMs displayed a similar immunogenicity profile, both in terms of the vaccine-induced preF-ELISA IgG and RSV neutralizing antibody titers. Both the fold-increases from baseline and antibody levels at Day 15 were similar in the two groups.
The reactogenicity and safety profiles were in general similar in the two groups and in line with previous reports with the vaccine.8,9,15 None of the reported SAEs was considered related to study vaccination, and no cases of vaccine-induced TTS were identified or reported during this study. VITT/TTS was considered an AESI in this study since it has been very rarely observed among persons receiving Janssen’s Ad26.COV2.S COVID-19 vaccine (JCOVDEN®), the vaccine that shares the same platform technology with the Ad26.RSV.preF/RSV preF protein vaccine.8 None of the study participants developed VITT/TTS post-vaccination. To date, no cases of VITT have been identified in clinical trials using the Ad26.RSV.preF/RSV preF protein vaccine or any other Ad26-based vaccines besides JCOVDEN®. The data from this study reflect the overall good tolerability of the Ad26.RSV.preF/RSV preF protein vaccine. No safety concerns were reported.
This study had limitations; the durability of the immune response was not assessed, thus not providing comparative head-to-head data in that regard with the two lots; and the immune response induced against RSV B was not measured, although these data are available in other studies.9
Conclusions
The primary objective of the study was met, and the humoral immune response, in terms of preF-ELISA antibody GMT, induced by the phase 3 CTM was non-inferior to that induced by the phase 2b CTM at Day 15. Globally, the immune response in the two groups was similar, and neutralizing antibody titers at Day 15 were similar in the phase 3 CTM and phase 2b CTM groups. The safety profile in terms of solicited AEs, unsolicited AEs, or SAEs was generally similar in the phase 3 CTM group and the phase 2b CTM group. No related SAEs were reported, and no safety concerns were identified. This suggests that changes in the manufacturing process between the phase 2b and phase 3 CTM had impact on the safety, immunogenicity, or efficacy profile of the vaccine.
Acknowledgments
We thank all the study participants and their families, the study investigators, and site personnel. Thanks also go to the Janssen study team.
Biographies
Archana Jastorff obtained a PhD in proteomics and neurogenerative disease from the Max Planck Institute of Psychiatry and University of Tuebingen, Germany. She has 14 y of experience in clinical research and development of vaccines and was Study Responsible Scientist for RSV vaccine clinical studies at Janssen Vaccines & Prevention until recently. She is now Senior Clinical Science Lead at GSK.
Arangassery Rosemary Bastian obtained a PhD in Biomedical Engineering from Drexel University. She has been at Janssen Inc for 6 y, as Director, Biomarkers Viral Vaccines, leading in particular the clinical biomarker strategy and immune response assessments for the RSV vaccine. She is now Director, Translational Sciences, at BioNTech SE.
Nynke Ligtenberg obtained a Masters in Biomedical Sciences from Leiden University. She has 30 y of experience, including at Janssen Pharmaceuticals, where she had global operational oversight of the Janssen vaccines clinical research portfolio, and most recently acted as Clinical Development Leader of the RSV vaccine development program.
Vladislav Klyashtornyy is an experienced biostatistician with more than 11 y of experience in supporting clinical phase 1 to phase 4 clinical studies. A doctor in medical chemistry from Krasnoyarsk State University, Russian Federation, with a further degree in molecular biology and biochemistry from Universite Evry Val d’Essone, France, he then trained as a biostatistician at the Institute for Statistical lead at Statistics.com, in the United States. He is Principal Biostatistician at IQVIA and Statistician lead for clinical programs at Janssen.
Benoît Callendret is a Doctor in Veterinary Medicine (Ecole Nationale Vétérinaire de Toulouse) and has a PhD in Virology and Immunology (Institut Pasteur, Universite Paris VII). He has more than 10 y of experience as program development lead with vaccines, in particular as a Compound Development Team Leader at Janssen Vaccines & Prevention, where he led the RSV vaccine program. He is now Infectious Diseases & Vaccine Development Team Leader at Moderna.
Esther Heijnen is a Medical Doctor specializing in gynecology. She has 20 years of experience of clinical development including 15 with vaccines. She was Senior Director, Global Clinical Development for respiratory vaccines at Janssen Vaccines & Prevention for 5 y, and she had in particular oversight of the clinical development of RSV vaccines. She is now Vice President, Clinical Development and R&D Co-lead for the vaccine therapeutic area leadership team with CSL Seqirus.
Funding Statement
This work was supported by Janssen Infectious Diseases & Vaccine during all stages of the trial and its analysis and during the development and publishing of the manuscript, including scientific writing assistance and statistical analyses.
Disclosure statement
V.K. is a full-time employee of the study sponsor. A.J., A.R.B., B.C., E.H., and N.L. were employees of the sponsor at the time of the trial. P.H. reports no potential conflicts.
Data availability statement
The data sharing policy of Janssen Pharmaceutical Companies of Johnson & Johnson is available at https://www.janssen.com/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at http://yoda.yale.edu.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data sharing policy of Janssen Pharmaceutical Companies of Johnson & Johnson is available at https://www.janssen.com/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at http://yoda.yale.edu.