Enabling the evaluation of COVID-19 vaccines with correlates of protection.

In February 2023, a meeting about correlates of protection (CoPs) against COVID-19 was organized by the International Alliance for Biological Standardization, the European Plotkin Institute for Vaccinology, and Vaccinopolis. The meeting aimed at reviewing the evidence, drawing conclusions, and identifying knowledge gaps. Collection of evidence is not straightforward. Neutralizing antibodies correlate with protection and are used for immunobridging studies within and between vaccine platforms for approval of new COVID-19 vaccines. In preparation for the next pandemic, it is vital that rapidly authorized initial vaccines are available to perform immunobridging studies very early. Additional components of the immune response likely contribute to protection against symptomatic infection. Current evidence is strongest for T lymphocytes and binding antibodies. Further studies are needed to consolidate this evidence and define their potential role in the evaluation of vaccines. For evaluation of mucosal vaccines, identifying CoPs against infection and transmission is key; further research is needed to identify and standardize methods suitable for clinical studies. CoPs for broadly protective beta-coronavirus vaccines remain a critical area of research. The knowledge, expertise, and capacity exist to conduct clinical studies using different designs in different populations to discover and validate CoPs, facilitating and accelerating evaluation of novel vaccines/vaccination platforms.

Approaches to demonstrating the effectiveness of filovirus vaccines: Lessons from Ebola and COVID-19.

Zaire ebolavirus (EBOV), Sudan ebolavirus (SUDV) and Marburg virus (MARV), are members of the Filoviridae family that can cause severe disease and death in humans and animals. The reemergence of Ebola, Sudan and Marburg virus disease highlight the need for continued availability of safe and effectives vaccines as well as development of new vaccines. While randomized controlled trials using disease endpoints provide the most robust assessment of vaccine effectiveness, challenges to this approach include the unpredictable size, location, occurrence and duration of filovirus disease outbreaks. Thus, other approaches to demonstrating vaccine effectiveness have been considered. These approaches are discussed using examples of preventive vaccines against other infectious diseases. In addition, this article proposes a clinical immunobridging strategy using licensed EBOV vaccines as comparators for demonstrating the effectiveness of filovirus vaccine candidates that are based on the same licensed vaccine platform technology.

Report of the second international conference on next generation sequencing for adventitious virus detection in biologics for humans and animals.

The IABS-EU, in association with PROVAXS and Ghent University, hosted the "2nd Conference on Next Generation Sequencing (NGS) for Adventitious Virus Detection in Human and Veterinary Biologics" held on November 13th and 14th 2019, in Ghent, Belgium. The meeting brought together international experts from regulatory agencies, the biotherapeutics and biologics industries, contract research organizations, and academia, with the goal to develop a scientific consensus on the readiness of NGS for detecting adventitious viruses, and on the use of this technology to supplement or replace/substitute the currently used assays. Participants discussed the progress on the standardization and validation of the technical and bioinformatics steps in NGS for characterization and safety evaluation of biologics, including human and animal vaccines. It was concluded that NGS can be used for the detection of a broad range of viruses, including novel viruses, and therefore can complement, supplement or even replace some of the conventional adventitious virus detection assays. Furthermore, the development of reference viral standards, complete and correctly annotated viral databases, and protocols for the validation and follow-up investigations of NGS signals is necessary to enable broader use of NGS. An international collaborative effort, involving regulatory authorities, industry, academia, and other stakeholders is ongoing toward this goal.

Clinical Development Strategies and Considerations for Zika Vaccine Licensure.

The Zika outbreak that began in 2015 has spread from Brazil to countries across the Western Hemisphere including the United States, presenting global public health challenges that call for the expedited development and availability of preventive vaccines to protect against Zika virus disease. While the general principles guiding the nonclinical and clinical development for Zika vaccines are the same as those of other preventive vaccines, unique considerations apply, in particular if development occurs during a public health emergency. Furthermore, incomplete information about the pathogenesis of Zika virus disease and the mechanism by which candidate preventive vaccines potentially may confer protection presents additional challenges to their clinical development. Nevertheless, definition of clinical development strategies to enable sound regulatory assessment, with a goal toward licensure is critical for these products. This article will provide an overview of the regulatory considerations for the clinical development and licensure of Zika vaccine candidates including a discussion of clinical study designs, approaches to demonstrate vaccine effectiveness, and regulatory pathways to licensure.

An overview of the regulation of influenza vaccines in the United States.

Influenza virus vaccines are unique among currently licensed viral vaccines. The vaccines designed to protect against seasonal influenza illness must be updated periodically in an effort to match the vaccine strain with currently circulating viruses, and the vaccine manufacturing timeline includes multiple, overlapping processes with a very limited amount of flexibility. In the United States (U.S.), over 150 million doses of seasonal trivalent and quadrivalent vaccine are produced annually, a mammoth effort, particularly in the context of a vaccine with components that usually change on a yearly basis. In addition, emergence of an influenza virus containing an HA subtype that has not recently circulated in humans is an ever present possibility. Recently, pandemic influenza vaccines have been licensed, and the pathways for licensure of pandemic vaccines and subsequent strain updating have been defined. Thus, there are formidable challenges for the regulation of currently licensed influenza vaccines, as well as for the regulation of influenza vaccines under development. This review describes the process of licensing influenza vaccines in the U.S., the process and steps involved in the annual updating of seasonal influenza vaccines, and some recent experiences and regulatory challenges faced in development and evaluation of novel influenza vaccines.

The US FDA pregnancy lactation and labeling rule - Implications for maternal immunization.

The FDA has responsibility for ensuring that prescription drug and biological products including vaccines are accompanied by labeling that summarizes scientific information concerning their safe and effective use. As part of a broader effort to improve the content and format of prescription drug labeling FDA published a final rule, the Content and Format of Labeling for Human Prescription Drug and Biological Products; Requirements for Pregnancy and Lactation Labeling, referred to as the "Pregnancy and Lactation Labeling Rule (PLLR)." The most significant change to be implemented by this Rule is the removal of the letter risk categories A, B, C, D and X from all labeling, replacing them with a narrative summary of the risks of using a drug or biological product including vaccines during pregnancy. The PLLR requires an evaluation of available information about a product's use in pregnancy and provides an opportunity to update labeling when new information about use of a vaccine in pregnancy becomes available. Implementation of the provisions articulated in the PLLR, as they apply to vaccine product labeling, will require close collaboration between FDA and the vaccine manufacturer for both currently licensed vaccines and those in development.

Immunology of protection from Ebola virus infection.

A December 2014 meeting reviewed Ebola virus immunology relevant to vaccine development, including Ebola prevention, immunity, assay standardization, and regulatory considerations. Vaccinated humans appear to achieve immune responses comparable in magnitude with those associated with protection in nonhuman primates, suggesting that immunological data could be used to demonstrate vaccine efficacy.

Regulatory considerations in the clinical development of vaccines indicated for use during pregnancy.

Despite supportive public health policies (e.g., ACIP recommendations), the potential for providing clinical benefit through maternal immunization has yet to be fully realized. For vaccines already licensed and approved for use in adults, specific FDA approval for use during pregnancy to prevent disease in the mother and/or infant may have a significant impact on uptake and usage in pregnant women. In addition, for either a licensed vaccine or a novel vaccine, FDA approval for use during pregnancy would result in labeling that would serve as a resource for practitioners and would facilitate the safe and effective use of the vaccine during pregnancy. In the U.S., while many vaccines are approved for use in adults and most are not contraindicated for use in pregnant women, no vaccine is licensed for use specifically during pregnancy. Among the perceived obstacles hindering the clinical development of vaccines for use in pregnancy, regulatory issues are frequently cited. One aim of this article is to address the perceived regulatory obstacles. General concepts and regulatory considerations for clinical safety and effectiveness evaluations for vaccines indicated for use during pregnancy will be discussed. This discussion is not intended to establish data requirements or to articulate agency policy or guidance regarding specific vaccine products.

Clinical evaluation of pertussis vaccines: US Food and Drug Administration regulatory considerations.

The resurgence of pertussis in the United States has stimulated considerable public health interest in developing new vaccination strategies to improve control of pertussis. The purpose of this article is to review the US Food and Drug Administration's regulatory framework for the prelicensure clinical evaluation of preventive vaccines and the clinical approaches that have been used to demonstrate effectiveness of US-licensed vaccines containing an acellular pertussis component.

US FDA review and regulation of preventive vaccines for infectious disease indications: impact of the FDA Amendments Act 2007.

Vaccines for prevention or treatment of infectious diseases are biological products that are regulated by the Office of Vaccines Research and Review in the Center for Biologics Evaluation and Research of the US FDA. The legal framework for the regulation of vaccines derives primarily from Section 351 of the Public Health Service Act and from certain sections of the Federal Food, Drug and Cosmetic Act (FFD & C Act). The FDA Amendments Act of 2007 (FDAAA 2007) includes extensive modifications to the FFD & C Act. This article provides an overview of the review process for preventive vaccines and highlights applicable statutory provisions. In addition, this article will discuss changes in the pre-and post-licensure evaluation process for preventive and therapeutic infectious disease vaccines since implementation of the FDAAA 2007.

Maternal immunization: US FDA regulatory considerations.

Vaccination of pregnant women provides important health benefits to both, mother and infant, and has been an important disease prevention strategy in these two groups. While most vaccines currently licensed in the US are not indicated for use during pregnancy, depending on the vaccine, vaccination programs do frequently include pregnant women. In addition, recent emphasis has been placed on maternal immunization strategies to protect young infants from severe infections. Currently, unless the vaccine is specifically indicated four maternal immunization, no data are collected regarding the vaccine's safety in pregnant women prior to licensure. However, more females of childbearing age participate in clinical trials and a broad range of novel vaccine products are in development indicated for adolescents and adults. Thus, there is increasing concern for the unintentional exposure of an embryo/fetus before information is available regarding the potential risk versus benefit of the vaccine. Since pregnant women are usually excluded from participation in clinical trials, conclusions regarding developmental risk at the time of licensure are frequently based solely on data derived from developmental toxicity studies in animal models. This paper will review regulatory, preclinical and clinical issues as they pertain to development programs for vaccines intended for vaccination during pregnancy.