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Panelists at the meeting will focus on clinical trial design, immunogenicity, and enhancing implementation plans for administering already-licensed vaccines to this patient population.
The FDA's Vaccines and Related Biological Products Advisory Committee will hold a meeting on Nov. 13, 2015 to discuss the benefits and risks associated with the use of maternal immunizations to protect infant health.
Vaccines that are already licensed and recommended for pregnant women include those for respiratory syncytial virus (RSV), the inactivated flu vaccine, and the combination vaccine for tetanus, diphtheria, and pertussis (Tdap). According to the FDA briefing document, there has been a surge in interest by vaccine developers in this patient population, and many investigational vaccines geared towards this population are already in early stages of development.
Expectant mothers already face numerous health risks simply as a result of being pregnant, argues an FDA briefing document released prior to the meeting, and investigational vaccines for use during pregnancy can be especially risky. Thus, the potential for clinical benefit has to significantly outweigh the various risks involved, which could include potentially life-threatening adverse inflammatory reactions. Specifically, the vaccine-associated inflammatory reaction that is necessary to generate an immune response in the mother “could disturb maternal mechanisms that maintain tolerance of foreign fetal antigens, potentially leading to adverse pregnancy outcomes, such as spontaneous abortion, intrauterine growth restriction, or preterm birth.”
Specifically, the documents raised questions about the ethical implications of trials with pregnant women for licensed products, saying that the placebo arms of these trials “may be considered unethical or present logistical challenges.” Similarly, measuring efficacy by clinical endpoints may also present ethical challenges, the document authors argue, and the measurement of immune markers to predict protection may be more feasible. Alternative study designs may be acceptable if there is compelling evidence that a randomized, controlled, blinded study is deemed unethical or not possible. In addition, meeting attendees will discuss best practices for post-marketing safety surveillance in both the mother and child.
Pursuing pregnancy-specific indications
Indications that target pregnant women should consider safety to both the baby and the mother throughout each stage of clinical development, and more serious reactions, such as hypertension and deep vein thrombosis, are more likely to occur in pregnant women. A framework for defining adverse events (i.e., whether they are more salient for the mother or the baby) may be required by sponsors. The Center for Biologics Evaluation and Research (CBER) wrote in the document that it is prepared to discuss the use of clinical data from a third party (the data that are typically used to support an efficacy supplement in a product’s biologics license application [BLA]) to support a licensure application seeking an indication for maternal vaccination.