Keys to Success in Vaccine Development for Special Populations

Vaccines are an incredible public health achievement, but developing them for pediatric and elderly populations can be complicated.

The global COVID-19 pandemic increased awareness of the importance of vaccine development — both for drug developers and the public. The speed at which COVID-19 vaccines were developed was remarkable, but like most newly developed vaccines, there was variation among who could receive the shots and when.

To effectively implement vaccine clinical trials for special populations, it is critical for vaccine developers to partner with a contract research organization (CRO) that has demonstrated experience recruiting and retaining pediatric and elderly study participants — and managing the nuances these patients and their caregivers require.

Because the immune system functions differently at various stages of life, vaccine developers have to take into account the traits of the immune system at each stage. Children and the elderly are among the most vulnerable populations and must be given special consideration in vaccine clinical trials to ensure their protection against vaccine-treatable diseases.

The many considerations of pediatric vaccine clinical trials

Childhood vaccines are highly effective in the prevention of many diseases. But enrolling and retaining pediatric patients in vaccine clinical trials is complex. From study participants’ consent, to minimizing the patient and caregiver burden, to planning for different needs at different stages of the pediatric immune system, there are many factors to consider when conducting clinical research with this specific population.

Emphasizing safety and ethics, reducing patient burden

Since 2001, the European Directive 2001/20/EC has provided foundational guidance for research involving children to ensure the highest level of safety and ethics. Some of the considerations include:

• Obtaining informed consent of parents or legal guardians and patient assent, when appropriate.
• Sharing information about the research, including risk and benefits, tailored to the patient’s level of understanding.
• Designing the clinical trials to minimize pain, discomfort, fear and any other foreseeable risk in relation to the disease and developmental stage.
• Having the protocol endorsed by an ethics committee with pediatric expertise or ensuring it takes advice in clinical, ethical and psychosocial problems in pediatrics.
• Placing the interests of the patient over those of science and society.
• Prohibiting any additional incentives or financial inducements beyond compensation.

Additionally, the European Medicines Agency offers guidance specific to the clinical investigation of medicinal products in pediatric populations. This guidance includes:

• Age classification and pediatric subgroups, including neonates
• Approaches to optimize pediatric drug development
• Commonality of scientific approach for pediatric drug development programs
• Ethical considerations
• Pediatric formulations
• Practicalities in the design and execution of pediatric clinical trials

Beyond ethical and safety considerations, vaccine developers must have a plan for pediatric populations early in their new candidate vaccine clinical development — whether the population is in infancy, childhood or adolescence. Pediatric patients will have a different response to vaccines than adults and their response will depend on their age and developmental stage.

Parents of pediatric clinical trial study participants must give informed consent, but, at a certain age, the patients themselves are required to assent after study risks and benefits are explained to them in developmentally appropriate language. The minimum age standards vary by country, and drug developers must be knowledgeable of the expectations in countries in which they conduct trials.

Ensuring that participation in the clinical trial does not place a burden on the children and their caregivers is key to pediatric vaccine clinical trial success. Site visits should be kept as short as possible, with the patient’s school and holiday schedule accommodated.

The importance of pediatric vaccine research

Although there is a recommended childhood vaccine schedule, ongoing research and development of preventative and therapeutic vaccines is important. The maturation of the immune system puts the pediatric population at increased risk for infectious disease.

To achieve success in pediatric clinical trials, you must be able to:

• Enroll and retain pediatric patients
• Understand and minimize the patient and caregiver burden
• Possess the scientific knowledge necessary to navigate the differences in the pediatric population

The team of pediatric vaccine experts at the PPD™ clinical research business of Thermo Fisher Scientific has supported more than 20 pediatric vaccine clinical trials and successfully enrolled 48,000 children into studies. Our recent partnership with a COVID-19 vaccine developer saw a 95% retention rate — one of the highest retention rates recorded in a clinical trial including children between the ages of 2-6 years old. The vaccine was deemed safe and highly immunogenic in the pediatric population between 2-17 years old.

The many considerations of elderly vaccine clinical trials

Vaccine development is just as important at the other end of the age spectrum. According to a report from the World Health Organization the global population of those age 60 and older reached 1 billion in 2020. By 2050, that number is expected to more than double to 2.1 billion.

With such a steep increase in the aging population, vaccine developers must anticipate and implement strategies for incorporating the needs of this group into study designs.

Historically, the elderly have been under-represented in clinical trials that include study participants 18 years of age and older. Data generated by these studies was generally extrapolated to the elderly general population. However, due to the pharmacokinetic and pharmacodynamic physiological changes that come with age and the presence of multi-morbidity, this type of extrapolation is not entirely appropriate.

As individuals age, their immune systems becomes weaker, and vaccines that lower the risk of contracting certain diseases in general adult populations may not have the same response in elderly populations. It is imperative for drug developers to understand how to develop effective vaccines for older patients.

New tactics for an aging population

In addition to weakening immune systems, older and geriatric populations present vaccine developers with several complex challenges. Aging patients may live on their own in a community dwelling or in a setting where assistance is provided. These settings range from senior villages, where the elderly live independently, to long-term care facilities, where the elderly rely on assistance for daily living.

Major factors that influence the willingness of the elderly to participate in clinical research include the presence of multiple co-morbidities, cognitive decline that comes with age, increased frailty and dependence on caregivers. Understanding these common factors — and the many other individual factors — allows successful implementation of clinical trials involving an elderly population.

Despite these challenges, there have been successes in vaccine development for older populations, including the flu, COVID-19 and shingles vaccines. Continued advancement in vaccine development for aging populations requires drug developers to be proactive in finding new ways to bring the trial to the patient. The patient experience can be simplified with digital and decentralized trial technologies including:

• eCOA
• eConsent
• Home health care
• Telehealth
• Wearables

A CRO that understands the barriers to access that elderly patients face and the burdens that they and their caregivers shoulder — and incorporates that knowledge into study designs — enables your geriatric vaccine clinical trials to function more seamlessly.

Choose a CRO partner with special populations vaccine development expertise

Advancing from a clinical trial to an authorization to a vaccine for special populations can be seamless with the right CRO partner. With more than 30 years of experience supporting more than 220 vaccine studies across 90 countries, the PPD clinical research business of Thermo Fisher Scientific has the expertise to drive your vaccine program forward.