Safety and Immunogenicity of a Respiratory Syncytial Virus Prefusion F Vaccine When Coadministered With a Tetanus, Diphtheria, and Acellular Pertussis Vaccine

Biomarkers of vaccine safety and efficacy in vulnerable populations: Lessons from the fourth international precision vaccines conference

Vaccination has been a cornerstone of public health, substantially reducing the global burden of infectious diseases, notably evident during the COVID-19 pandemic caused by SARS-CoV-2. However, vulnerable populations (VPs), including those in extreme age groups and those with underlying health conditions, have borne a disproportionate burden of morbidity and mortality from infectious diseases. Understanding vaccine immunogenicity in these populations is crucial for developing effective vaccines. Characterizing vaccine responses in VPs presents unique challenges due to under-vaccination, sub-optimal vaccine responses, and distinct mechanisms of vaccine-induced protection. To address these challenges, experts convened at the 4th International Precision Vaccines Conference in Rome. Co-hosted by the Precision Vaccines Program of Boston Children's Hospital and Ospedale Pediatrico Bambino Gesù, the conference focused on biomarkers of vaccine safety and efficacy in vulnerable populations. Discussions at the conference emphasized the need for multidisciplinary strategies and international collaborations to optimize vaccine development. Key areas of focus included assessing vaccine safety, defining biomarkers for vaccine immunogenicity, developing human in vitro assay models, and accelerating the selection of novel vaccine formulations and adjuvants tailored for vulnerable populations. The conference provided a platform for experts from diverse fields, including immunology, paediatrics, and vaccinology, to exchange ideas and advance research in precision vaccines. This manuscript highlights key concepts discussed at the conference and underscores the importance of precision vaccines in addressing the unique needs of vulnerable populations.

Safety, Efficacy, and Effectiveness of Maternal Vaccination against Respiratory Infections in Young Infants

Lower respiratory tract infection (LRTI) is a major cause of neonatal morbidity and mortality worldwide. Maternal vaccination is an effective strategy in protecting young infants from LRTI, particularly in the first few months after birth when infant is most vulnerable, and most primary childhood vaccinations have not been administered. Additionally, maternal vaccination protects the mother from illness during pregnancy and the postnatal period, and the developing fetus from adverse outcomes such as stillbirth and prematurity. In this paper, we review the safety, efficacy, and effectiveness of maternal vaccines against LRTIs, such as pertussis, influenza, coronavirus disease 2019, and respiratory syncytial virus.

The respiratory syncytial virus vaccine and monoclonal antibody landscape: the road to global access

Respiratory syncytial virus (RSV) is the second most common pathogen causing infant mortality. Additionally, RSV is a major cause of morbidity and mortality in older adults (age ≥60 years) similar to influenza. A protein-based maternal vaccine and monoclonal antibody (mAb) are now market-approved to protect infants, while an mRNA and two protein-based vaccines are approved for older adults. First-year experience protecting infants with nirsevimab in high-income countries shows a major public health benefit. It is expected that the RSV vaccine landscape will continue to develop in the coming years to protect all people globally. The vaccine and mAb landscape remain active with 30 candidates in clinical development using four approaches: protein-based, live-attenuated and chimeric vector, mRNA, and mAbs. Candidates in late-phase trials aim to protect young infants using mAbs, older infants and toddlers with live-attenuated vaccines, and children and adults using protein-based and mRNA vaccines. This Review provides an overview of RSV vaccines highlighting different target populations, antigens, and trial results. As RSV vaccines have not yet reached low-income and middle-income countries, we outline urgent next steps to minimise the vaccine delay.

A Statistical Model to Predict Protection Against Infant Respiratory Syncytial Virus Disease Through Maternal Immunization

BACKGROUND/OBJECTIVES

Respiratory syncytial virus (RSV) is the leading cause of severe respiratory disease in infants worldwide. Maternal immunization to protect younger infants is supported by evidence that virus-neutralizing antibodies, which are efficiently transferred across the placenta from mother to fetus, are a primary immune mediator of protection. In maternal RSV vaccine studies, estimates of correlates of protection are elusive because many factors of maternal-fetal immunobiology and disease characteristics must be considered for the estimates.

METHODS

We developed statistical models that aims to predict vaccine efficacy (VE) in infants following maternal immunization by including quantifiable covariates of the antibody titer distribution of the mother (pre- and post-immunization), the transplacental transfer ratio of IgG antibodies, the rate of antibody decay, and RSV disease incidence rate, all of which are season- and time-dependent and vary by infant age.

RESULT

Our model shows that integrating the lower respiratory tract disease risk based on infant airway diameter and associated airway resistance is critical to appropriately model predicted infant VE. The VE predictions by our models, which preceded maternal RSV prefusion F vaccine efficacy trial primary readouts, closely align with the VE outcomes of these field studies.

CONCLUSION

Our models successfully predicted VE of the RSV maternal vaccines and have potential use in modeling the clinical trial out-comes of other respiratory disease vaccines where maternal antibodies play a role in the protection of newborns.

Respiratory Syncytial Virus Vaccination in the Adult Pulmonary Patient

TOPIC IMPORTANCE

Since its discovery in 1957, respiratory syncytial virus (RSV) has been widely recognized as a common and deadly pathogen. Although early studies focused on the impact of RSV on the health of children, more recent data show that RSV imposes a significant burden on individuals aged ≥ 70 years. RSV also substantially harms the health of individuals with cardiopulmonary diseases.

REVIEW FINDINGS

Early efforts to develop an RSV vaccine were hampered by toxicity due to antibody-enhanced viral pneumonia and a lack of efficacy in vaccines that targeted the postfusion configuration of the F fusion protein, which is crucial to the pathogenesis of RSV-mediated injury. A newer wave of vaccines has targeted a stabilized prefusion F protein, generating effective neutralizing antibodies and reducing the burden of mild and severe RSV lower respiratory tract injury. This review focuses on the burden of RSV in patients with pulmonary diseases, highlights the tumultuous path from the early days of RSV vaccine development to the modern era, and offers insights into key gaps in knowledge that must be addressed to adequately protect the vulnerable population of patients with severe pulmonary diseases.

SUMMARY

RSV vaccination with bivalent RSVPreF or RSVPreF3OA, which target the stabilized prefusion F protein, can be broadly recommended to adults aged ≥ 60 years with pulmonary diseases. However, more data are needed to understand how these vaccinations affect key clinical outcomes in individuals with pulmonary disease.

Maternal Vaccination for the Prevention of Infantile RSV Disease: An Overview of the Authorized, In-Progress, and Rejected Vaccine Candidates

Respiratory Syncytial Virus (RSV) continues to pose a significant challenge, contributing to elevated hospitalization rates among children up to 5 years old, with a disproportionate burden on newborns and infants under 6 months old. The unique characteristics of the young immune system make it prone to altered responses to infections and vaccinations, requiring a tailored approach to disease prevention. The recent approval of the maternal RSV vaccine (brand name ABRYSVO) represents a pivotal advancement in preventive strategies among newborns and infants, marking a milestone in RSV research as the first market-approved maternal vaccine. The present review examines clinical trial data on both recent and previous vaccine candidates, as well as the licensed vaccine, focusing on the prevention of RSV disease in newborns and young infants through the passive acquisition of antibodies following maternal immunization. Additionally, it evaluates the safety profile of these vaccines.

Safety and Immunogenicity of Respiratory Syncytial Virus Prefusion Maternal Vaccine Coadministered With Diphtheria-Tetanus-Pertussis Vaccine: A Phase 2 Study

BACKGROUND

Respiratory syncytial virus (RSV) fusion protein stabilized in the prefusion conformation (RSVPreF3) was under investigation as a maternal vaccine.

METHODS

This phase 2, randomized, placebo-controlled, single-dose, multicenter study enrolled healthy, nonpregnant women, randomized 1:1:1:1:1 to 5 parallel groups studying RSVPreF3 (60 or 120 µg) coadministered with diphtheria, tetanus, and acellular pertussis vaccine (dTpa) or placebo, and dTpa coadministered with placebo. Safety and humoral immune responses were assessed. An extension phase also assessed a RSVPreF3 120 μg vaccination 12-18 months after first vaccination.

RESULTS

The safety profile of RSVPreF3 was unaffected by dose or dTpa coadministration. Solicited and unsolicited adverse events (AEs) were evenly distributed across study groups. Injection-site pain was higher following the second vaccination versus the first vaccination. Medically attended AEs were rare (<5% overall). Both RSVPreF3 dose levels (alone and with dTpa) were immunogenic, increasing levels of RSV-A neutralizing antibody ≥8-fold and anti-RSVPreF3 IgG antibody ≥11-fold at 1 month postvaccination, which persisted at 12-18 months postvaccination; modest 2-fold increases were observed with a second RSVPreF3 vaccination.

CONCLUSIONS

This study indicates RSVPreF3 coadministration with dTpa induces robust immune responses and is well tolerated, regardless of the RSVPreF3 dose level used.

CLINICAL TRIALS REGISTRATION

NCT04138056.

Efficacy, immunogenicity and safety of respiratory syncytial virus prefusion F vaccine: systematic review and meta-analysis

OBJECTIVE

A notable research gap exists in the systematic review and meta-analysis concerning the efficacy, immunogenicity, and safety of the respiratory syncytial virus (RSV) prefusion F vaccine.

METHODS

We conducted a comprehensive search across PubMed, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov to retrieve articles related to the efficacy, immunogenicity, and safety of RSV prefusion F vaccines, published through September 8, 2023. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

A total of 22 randomized controlled trials involving 78,990 participants were included in this systematic review and meta-analysis. The RSV prefusion F vaccine exhibited a vaccine effectiveness of 68% (95% CI: 59-75%) against RSV-associated acute respiratory illness, 70% (95% CI: 60-77%) against medically attended RSV-associated lower respiratory tract illness, and 87% (95% CI: 71-94%) against medically attended severe RSV-associated lower respiratory tract illness. Common reported local adverse reactions following RSV prefusion F vaccination include pain, redness, and swelling at the injection site, and systemic reactions such as fatigue, headache, myalgia, arthralgia, nausea, and chills.

CONCLUSIONS

Our meta-analysis suggests that vaccines using the RSV prefusion F protein as antigen exhibit appears broadly acceptable efficacy, immunogenicity, and safety in the population. In particular, it provides high protective efficiency against severe RSV-associated lower respiratory tract disease.

Recent advances in the prevention of respiratory syncytial virus in pediatrics

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) is a ubiquitous virus and the leading cause of pediatric hospitalization in the United States. Prevention strategies are key for reducing the burden of RSV. Several new agents aimed at preventing RSV in infants and children were FDA-approved in 2023, and many more are in the development pipeline. This review highlights new developments in RSV prevention in pediatric patients and the important safety considerations for clinical trials.

RECENT FINDINGS

Two new preventive therapies were FDA approved in 2023; a maternal vaccine (Abrysvo) and a mAb (Beyfortus) have both demonstrated reduction in medically attended lower respiratory tract infections in infants and children. Evaluation of ongoing clinical trials demonstrates that the field is expanding further to include direct immunization of infants and children utilizing a variety of delivery modalities. While these developments present the optimistic prospect of RSV prevention in a range of ages, acute and long-term risks must be carefully evaluated.

SUMMARY

Prevention of RSV is more accessible than ever, but careful consideration must be given to risks associated with new and developing prevention strategies. Rigor of clinical trials including longitudinal outcomes of agents in development and postmarketing surveillance of newly approved therapies will be of paramount importance to ensure long-term safety of new RSV prevention strategies.

Understanding New Recommendations for Respiratory Syncytial Virus Prevention in Pregnancy

Respiratory syncytial virus (RSV) is a significant cause of infant morbidity and mortality worldwide with peak hospitalization rates for RSV-mediated illnesses between 2 and 3 months of life. Until very recently, prevention strategies for RSV involved primarily passive immunization of neonates at high risk with monoclonal antibodies and promotion of breastfeeding. The Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices now recommends passive immunization of all neonates with monoclonal antibodies during RSV season, and the American Association of Pediatrics has endorsed this practice. The U.S. Food and Drug Administration (FDA) recently approved a vaccination for RSV in pregnancy. The CDC's Advisory Committee on Immunization Practices has recently recommended RSV vaccination for all pregnant patients between 32 and 36 weeks of gestation who are anticipated to deliver during RSV season if they are not planning nirsevimab for their infants. This recommendation has been endorsed by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine. In this clinical perspective, we review the scientific evidence, potential concerns, challenges, and future considerations for RSV vaccination in pregnancy.

Co-administration of the adjuvanted recombinant zoster vaccine with other adult vaccines: An overview

BACKGROUND

The adjuvanted recombinant zoster vaccine (RZV; Shingrix®, GSK) is a subunit vaccine that has been approved for the prevention of herpes zoster in adults. Co-administration of two vaccines in a single visit is a strategy to improve overall vaccine coverage.

OBJECTIVES

This review aims to consolidate available clinical data on RZV co-administration, providing an overview of safety, reactogenicity and immunogenicity.

METHODS

RZV co-administration data were obtained from five randomised, open-label, phase III clinical trials with similar study designs. The co-administered vaccines included: quadrivalent seasonal inactivated influenza vaccine (IIV4; NCT01954251), 23-valent pneumococcal polysaccharide vaccine (PPSV23; NCT02045836), reduced-antigen-content diphtheria-tetanus-acellular pertussis vaccine (Tdap; NCT02052596), 13-valent pneumococcal conjugate vaccine (PCV13; NCT03439657) and COVID-19 mRNA-1273 booster (NCT05047770). Eligible participants were healthy adults aged ≥50 years.

RESULTS

A total of 3,974 participants were vaccinated (co-administration: 1,973; sequential: 2,001) across the five trials. Vaccine response rates to RZV were similar for co-administration (range: 95.8-99.1 %) and sequential groups (range: 95.1-99.1 %). Immune responses to RZV and the other vaccines (with the exception of pertactin) were non-inferior when the vaccines were co-administered compared with sequentially administered. Overall incidences of solicited local and general adverse events (AEs), unsolicited AEs, serious AEs or potential immune-mediated diseases were similar after co-administration or sequential administration. Myalgia was the most common solicited systemic AE (co-administration: 38-64 %; sequential: 30-59 %). Shivering and fever were more common after co-administration (16 % and 21 %, respectively) than after sequential administration (both 7 %) of RZV and PPSV23.

CONCLUSIONS

Co-administration of RZV with routine vaccines does not significantly alter the reactogenicity, immunogenicity or safety of RZV or the co-administered vaccine. Healthcare practitioners should consider routine co-administration of RZV with other adult vaccines to improve vaccination coverage.

Protecting infants against RSV disease: an impact and cost-effectiveness comparison of long-acting monoclonal antibodies and maternal vaccination

Background

Two new products for preventing Respiratory Syncytial Virus (RSV) in young children have been licensed: a single-dose long-acting monoclonal antibody (la-mAB) and a maternal vaccine (MV). To facilitate the selection of new RSV intervention programmes for large-scale implementation, this study provides an assessment to compare the costs of potential programmes with the health benefits accrued.

Methods

Using an existing dynamic transmission model, we compared maternal vaccination to la-mAB therapy against RSV in England and Wales by calculating the impact and cost-effectiveness. We calibrated a statistical model to the efficacy trial data to accurately capture their immune waning and estimated the impact of seasonal and year-round programmes for la-mAB and MV programmes. Using these impact estimates, we identified the most cost-effective programme across pricing and delivery cost assumptions.

Findings

For infants under six months old in England and Wales, a year-round MV programme with 60% coverage would avert 32% (95% CrI 22-41%) of RSV hospital admissions and a year-round la-mAB programme with 90% coverage would avert 57% (95% CrI 41-69%). The MV programme has additional health benefits for pregnant women, which account for 20% of the population-level health burden averted. A seasonal la-mAB programme could be cost-effective for up to £84 for purchasing and administration (CCPA) and a seasonal MV could be cost-effective for up to £80 CCPA.

Interpretation

This modelling and cost-effectiveness analysis has shown that both the long-acting monoclonal antibodies and the maternal vaccine could substantially reduce the burden of RSV disease in the infant population. Our analysis has informed JCVI's recommendations for an RSV immunisation programme to protect newborns and infants.

Funding

National Institute for Health Research.

Prenatal Maternal Immunization for Infant Protection: A Review of the Vaccines Recommended, Infant Immunity and Future Research Directions

Prenatal maternal immunization is an effective tool to protect mothers and infants from poor health outcomes due to infectious diseases. We provide an overview of the rationale for the use of prenatal vaccines, discuss the immunologic environment of the maternal-fetal interface including the impact of maternal vaccines prenatally and subsequently on the infant's immune response, and review vaccines currently recommended in pregnancy and landscape for the future of maternal vaccination. This review aims to provide an understanding of the recent history and progress made in the field and highlight the importance of continued research and development into new vaccines for pregnant populations.

Society for Maternal-Fetal Medicine Statement: Clinical considerations for the prevention of respiratory syncytial virus disease in infants

Respiratory syncytial virus is a leading cause of lower respiratory tract illness globally in children aged <5 years. Each year, approximately 58,000 hospitalizations in the United States are attributed to respiratory syncytial virus. Infants aged ≤6 months experience the most severe morbidity and mortality. Until recently, prevention with the monoclonal antibody, palivizumab, was only offered to infants with high-risk conditions, and treatment primarily consisted of supportive care. Currently, 2 products are approved for the prevention of respiratory syncytial virus in infants. These include the Pfizer bivalent recombinant respiratory syncytial virus prefusion F protein subunit vaccine, administered seasonally to the pregnant person between 32 0/7 and 36 6/7 weeks of gestation, and the monoclonal antibody, nirsevimab, administered to infants aged up to 8 months entering their first respiratory syncytial virus season. With few exceptions, administering both the vaccine to the pregnant person and the monoclonal antibody to the infant is not recommended. All infants should be protected against respiratory syncytial virus using one of these strategies. Key considerations for pregnant individuals include examining available safety and efficacy data, weighing accessibility and availability, and patient preferences for maternal vaccination vs infant monoclonal antibody treatment. It will be critical for maternal-fetal medicine physicians to provide effective and balanced counseling to aid patients in deciding on a personalized approach to the prevention of respiratory syncytial virus in their infants.

Clinical research on RSV prevention in children and pregnant women: progress and perspectives

Respiratory syncytial virus (RSV) is a significant causative agent of bronchitis and pneumonia in infants and children. The identification and structural analysis of the surface fusion glycoprotein of RSV represents a pivotal advancement in the development of RSV prevention. This review provides a comprehensive summary of RSV monoclonal antibody (mAb) and vaccine clinical trials registered on ClinicalTrials.gov, emphasizing on the classification, name, target, phase, clinical outcomes, and safety data of RSV vaccination in newborns, infants and children. We also discuss the characteristics of the types of RSV vaccines for maternal immunity and summarize the current clinical research progress of RSV vaccination in pregnant women and their protective efficacy in infants. This review will provide new ideas for the development of RSV prevention for children in the future.

Vaccination for Respiratory Syncytial Virus: A Narrative Review and Primer for Clinicians

Respiratory syncytial virus (RSV) poses a significant burden on public health, causing lower respiratory tract infections in infants, young children, older adults, and immunocompromised individuals. Recent development and licensure of effective RSV vaccines provide a promising approach to lessening the associated morbidity and mortality of severe infections. This narrative review aims to empower clinicians with the necessary knowledge to make informed decisions regarding RSV vaccination, focusing on the prevention and control of RSV infections, especially among vulnerable populations. The paper explores the available RSV vaccines and existing evidence regarding their efficacy and safety in diverse populations. Synthesizing this information for clinicians can help the latter understand the benefits and considerations associated with RSV vaccination, contributing to improved patient care and public health outcomes.

Respiratory Syncytial Virus Prefusion F Subunit Vaccine: First Approval of a Maternal Vaccine to Protect Infants

Pfizer is developing a bivalent respiratory syncytial virus (RSV) prefusion F subunit vaccine (RSVpreF; ABRYSVO™) for preventing RSV illness in infants and individuals aged ≥ 60 years. RSVpreF received approval for vaccination of pregnant individuals to help protect infants against RSV illness on 21 August 2023 in the USA. RSVpreF is also approved in the USA (31 May 2023) for active immunization of individuals aged ≥ 60 years for the prevention of lower respiratory tract disease (LRTD) caused by RSV. In the EU, RSVpreF has received approval for both indications, and it has been submitted for regulatory approval in Canada (both indications) and in Japan (maternal immunization to protect infants). This article summarizes the milestones in the development of RSVpreF leading to the approval for use in pregnant individuals to prevent LRTD in infants.

Respiratory Syncytial Virus Vaccines: A Review of the Candidates and the Approved Vaccines

Respiratory syncytial virus (RSV) is responsible for a significant proportion of global morbidity and mortality affecting young children and older adults. In the aftermath of formalin-inactivated RSV vaccine development, the effort to develop an immunizing agent was carefully guided by epidemiologic and pathophysiological evidence of the virus, including various vaccine technologies. The pipeline of RSV vaccine development includes messenger ribonucleic acid (mRNA), live-attenuated (LAV), subunit, and recombinant vector-based vaccine candidates targeting different virus proteins. The availability of vaccine candidates of various technologies enables adjustment to the individualized needs of each vulnerable age group. Arexvy® (GSK), followed by Abrysvo® (Pfizer), is the first vaccine available for market use as an immunizing agent to prevent lower respiratory tract disease in older adults. Abrysvo is additionally indicated for the passive immunization of infants by maternal administration during pregnancy. This review presents the RSV vaccine pipeline, analyzing the results of clinical trials. The key features of each vaccine technology are also mentioned. Currently, 24 vaccines are in the clinical stage of development, including the 2 licensed vaccines. Research in the field of RSV vaccination, including the pharmacovigilance methods of already approved vaccines, promotes the achievement of successful prevention.

Current strategies and perspectives for active and passive immunization against Respiratory Syncytial Virus in childhood

OBJECTIVES

Despite the global impact of the Respiratory Syncytial Virus (RSV) infection in children, only one monoclonal antibody (Palivizumab) has been approved for clinical use. However, advances in the knowledge of RSV immunology may enable the development of safe and effective new vaccines and monoclonal antibodies in a few years. The purpose of this review is to summarize available data on approved and developing passive and active immunizations against RSV in childhood and pregnancy.

DATA SOURCE

A non-systematic review of RSV immunoprophylaxis in childhood and pregnancy was carried out in PubMed, path.org and clinical trial registries, without language restrictions, up to September 2022.

DATA SYNTHESIS

Three monoclonal antibodies and 17 active immunization candidates are under development in phase 1 to 3 clinical studies. Regarding the first group, Nirsevimab is a monoclonal antibody with a prolonged half-life whose approval for clinical use is expected in the next months. Among the vaccines under development, six techniques are being used: protein subunit, viral particles, live attenuated virus, recombinant viral vector, chimeric, and mRNA. The first two approaches are being tested primarily in pregnancy, while the others are being developed for the pediatric population.

CONCLUSIONS

The approval of extended half-life monoclonal antibodies is the next expected advance in RSV prevention, although the costs may be a barrier to the implementation. Regarding active immunizations, maternal and infant vaccination are complementary strategies and there are many promising candidates in clinical studies using different platforms.