Vaccines are among the most cost-effective health interventions against pathogens and other infectious diseases, saving millions of lives annually while improving quality of life for countless others. Growing global demand, however, poses severe challenges for vaccine manufacturers. Each new pathogen or outbreak adds to the variety of vaccine types and manufacturing methods needed, preventing establishment of robust processing templates that could improve overall effectiveness, safety, and affordability. Manufacturers must instead develop customized approaches that extend the boundaries of life science, while at the same time accelerating production of desperately needed vaccines with efficiency and cost-effectiveness.
From a manufacturing perspective, many factors are critical to accelerating vaccine production and meeting performance goals. These include predictable scale-up, optimal upstream productivity, robust impurity removal, maximized downstream recovery, speed to clinic, patient safety, and regulatory compliance. Achieving process improvements can drive success for all of the vaccine development platforms described below, but innovative technologies and a high level of application expertise are required.
By attenuating viruses to render them harmless while retaining their immunogenic profile, viral vaccines offer quick immunity, activate all phases of the immune system, and provide durable long-term immunity. The manufacturing process for each viral-based vaccine (VBV) is different, dictated by virus shape, size, nature, physico-chemical behavior, stability, and host specificity. An important challenge is to keep the attenuated virus live while maintaining the infective potential of the viral vaccine throughout downstream processing and formulation, until it is administered to healthy individuals.
A virus-like particle is a biological nanoparticle consisting of the protective protein shell of a virus without its genome. Mimicking the overall structure of virus particles but lacking infectious genetic material, they represent an appealing model for vaccine development. VLPs can be produced by methods such as mammalian cell culture, insect cell culture, and bacterial and yeast-based systems. While these systems can result in good production yields, purification requires particular attention. The challenge is to develop a scalable upstream process, together with clarification steps and effective purification, while ensuring product quality and reproducibility.
Viral vectors are a promising platform for vaccine development, inducing cell-mediated immunity against complex diseases such as Ebola, RSV, COVID-19, and other emerging threats. They also offer quick-response potential to repurpose a single virus production template for multiple diseases. However, viral vector processes can pose challenges: improving yield to meet patient demand, maintaining biosafety testing standards for product characterization, potency and safety, as well as streamlining time-consuming production to enhance commercial readiness and accelerate therapy to-market. Manufacturers that overcome these challenges can capitalize on viral vector platform opportunities, while improving the response to global health challenges.
mRNA/DNA vaccines are an emerging but rapidly developing vaccine type. Nucleic acids are based either on messenger RNA (mRNA), which are synthesized in in vitro systems, or on DNA formed from a fermentation process. They induce or promote an immune response against a large number of potential pathogens. These DNA/RNA vaccines are growing in popularity because of their quick turnaround time and cost-effective production of large quantities in the event of an outbreak or pandemic. They are also resilient and offer long shelf life under a variety of storage conditions.
Conjugated polysaccharide (CPS) vaccines are used globally, particularly in children and the developing world. They offer lifesaving protection against a variety of bacterial infections, including pneumonia, Haemophilus influenzae type b (Hib), and meningitis. Because polysaccharide antigens are not very immunogenic in their native state, chemical conjugation with an immunogenic carrier protein is a critical step. CPS vaccine production requires a complex, multi-step downstream purification process that can pose severe challenges for manufacturers under pressure to maximize yield and reduce costs. To keep CPS vaccines affordable for developing countries, state-of-the-art technologies and process design are essential for fast, cost-effective production that also meets specifications.
Toxoid and whole bacteria vaccines induce immunity in a similar manner as CPS vaccines, which also utilize inactivated toxoids or bacteria via chemical conjugation. While these platforms are generally regarded as safe, there are process-related challenges with endotoxin removal and, as with any process, the goal of optimizing recovery and yield. Such challenges must be overcome during process development and implementation in order to assure high-quality product.