Key Facts about Vaccines
Vaccines are biological preparations that train the immune system to recognize and fight pathogens, and they remain one of the most cost-effective tools in public health. Modern vaccine production relies on cell culture-based platforms, where well-characterized animal cell lines or microbial hosts replicate the antigen of interest under tightly controlled conditions in a bioreactor.
There are several vaccine modalities relevant for cell culture–based vaccine manufacturing: live-attenuated and inactivated viral vaccines, recombinant subunit vaccines, virus-like particles (VLPs), viral vector vaccines, and DNA/mRNA vaccines. Each modality has distinct upstream process requirements, but they share a common need for sterility, scalability, and reproducibility — properties that single-use bioreactors and stainless-steel systems are specifically designed to deliver.
Because most viral vaccines depend on a productive host cell, virus yield is shaped by the cell line, the medium, the bioreactor design, and the physicochemical environment (pH, dissolved oxygen, temperature, shear). Adherent cell lines such as Vero are typically grown on microcarriers, while suspension-adapted lines (e.g., suspension MDCK, PER.C6, suspension Vero, CHO) enable higher densities and easier scale-up. The choice between these strategies directly impacts process intensification, single-use bioreactor selection, and the achievable viral titer.
These properties define the design space for vaccine bioreactors and explain why precise control of pH, dissolved oxygen, temperature, and shear, combined with flexible single-use technology, is essential for both clinical and large-scale GMP vaccine manufacturing.
Typical Cell Types Used for Vaccines
Vaccine production relies on a small number of well-characterized, regulator-accepted host cell lines. The choice of host depends on the virus to be propagated, the desired modality (live-attenuated, inactivated, recombinant, viral vector), and the targeted scale. Each cell line has specific cultivation requirements that drive bioreactor selection and process design.
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Vero cells
African green monkey kidney
Continuous adherent line; the most widely used substrate for viral vaccine production for over 25 years (polio, rabies, rotavirus, SARS-CoV-2). Traditionally grown on microcarriers; suspension-adapted Vero is gaining traction for scalable manufacturing.
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MDCK cells
Madin-Darby canine kidney
The leading platform for cell culture–derived influenza vaccines. Suspension-adapted MDCK is commonly cultivated in single-use bioreactors with ATF perfusion to reach high cell densities.
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CHO cells
Chinese hamster ovary
Primarily used for recombinant subunit vaccines and viral protein expression (e.g., SARS-CoV-2 spike protein). Robust, suspension-capable, and a workhorse for biotherapeutics manufacturing.
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HEK293 cells
Human embryonic kidney
Widely used for viral vector–based vaccines (e.g., adenovirus vectors) and transient expression of recombinant antigens.
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PER.C6 and AGE1.CR
Designer human / avian lines
Grow in suspension at high densities (>10⁷ cells/mL) in serum-free medium and support a broad range of viruses, including influenza.
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BHK-21 cells
Baby hamster kidney
Predominantly used in veterinary vaccine production (e.g., FMD virus) on microcarriers.
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Microbial hosts
E. coli, yeast
Used for recombinant subunit antigens (e.g., HBV surface antigen in yeast, plasmid DNA in E. coli for DNA/mRNA vaccine starting materials).
Standard Process Workflow for Vaccines
Cell culture–based vaccine production follows a sequential workflow from working cell bank thaw through virus harvest. The workflow is adaptable to batch, fed-batch, and perfusion modes, and supports both adherent (microcarrier) and suspension processes.
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Seed train and cell expansion
Working cell bank vials are thawed and expanded in shake flasks or small-scale bioreactors (e.g., MiniBio) to generate sufficient inoculum for the production bioreactor; perfusion in N-1 supports high seeding densities.
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Inoculation of the production bioreactor
Cells are transferred at a defined density into the production vessel; for adherent processes, microcarriers are equilibrated and inoculated to ensure uniform attachment.
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Cell growth phase
Cascade control of pH, DO, and temperature, combined with feeds, drives cells to the target density required for productive infection or recombinant expression.
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Virus infection / induction
For viral vaccines, cells are infected at a defined MOI; medium exchange or temperature shifts may be applied. For recombinant subunit vaccines, expression is induced according to the host system.
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Virus production phase
Tight control of pH, DO, temperature, and shear maintains productive cells and protects fragile virus particles or antigens until peak titer.
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Process monitoring
Viable cell density (VCD), metabolites, and virus titer (TCID50, HA, qPCR) are tracked using off-line, at-line, and in-line PAT tools.
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Harvest
Single batch harvest, multiple harvests, or continuous harvest with cell retention; clarification removes microcarriers and cellular debris before downstream purification, inactivation, and formulation with adjuvants.
Key Process Parameters for Vaccines
Viral and recombinant vaccine processes are highly sensitive to the cultivation environment. Tight control of physicochemical parameters in the bioreactor directly affects host cell growth, virus replication kinetics, antigen quality, and final viral titer.
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pH Control
6.8–7.3
Maintained via CO2 sparging and base addition. Tight pH control protects shear-sensitive vaccine cell lines and stabilizes viral envelope and surface antigens.
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Dissolved Oxygen
DO 30–50 %
Regulated through air/O2 mixing and agitation. Adequate DO supports cell expansion; in many viral processes DO is held ≥50 % saturation throughout growth and infection.
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Temperature
37 °C + shifts
Standard at 37 °C for mammalian cell expansion, with virus-specific temperature shifts to 32–34 °C post-infection to optimize virus replication and antigen stability.
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Shear Minimization
Poloxamer -188
Low impeller speeds and adapted impeller geometries (marine, pitched-blade) protect adherent cells on microcarriers and shear-sensitive viral envelopes. Poloxamer-188 is commonly added to limit bubble-induced damage.
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Multiplicity of Infection
MOI 10⁻⁴–10⁻¹
Defines the virus-to-cell ratio at infection and is a key driver of virus yield, infection synchronicity, and downstream antigen quality.
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Microcarriers
2 g/L Cytodex-1
For adherent cell lines (Vero, MDCK, BHK-21), microcarrier loading and minimum suspension speed are tuned to ensure homogeneous cell attachment and growth.
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Nutrients & Metabolites
Glc / Gln / Lactate
Glucose / glutamine feeding, lactate and ammonia control are essential for sustaining viability through both the cell expansion and virus production phases — especially in perfusion and intensified processes.
The Role of Applikon Single-Use Bioreactors in Vaccine Production
Through its precision, versatility, safety, and scalability, the AppliFlex ST single-use bioreactor exemplifies the cutting-edge technology that will continue to drive innovations in vaccine development and manufacturing — enabling fast responses to emerging health threats. For large-scale production, it pairs with stainless-steel bioreactors covering the full commercial range up to 5000 L.
Applikon Bioreactor Types for Vaccine Production
Across all stages of vaccine research and manufacturing — from media screening and process development to clinical and commercial GMP production — Applikon bioreactors offer a scalable platform that supports adherent, microcarrier, and suspension-based vaccine processes.
| Type | Scale | Key Use Cases | Vaccine-Specific Features |
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| Applikon MiniBio glass small-scale bioreactor |
250 mL – 1 L | Vaccine process development, cell line and media screening, MOI screening, scale-down models | Low working volume reduces costly serum-free media spend; parallel multi-vessel setups; fine pH/DO/T control for sensitive Vero, MDCK, HEK293; perfusion-ready |
| Applikon glass autoclavable bioreactors for vaccine cell culture |
2–20 L | Microcarrier process optimization, virus seed train, scale-up/scale-down studies for viral vaccine production | Multi-gas sparging; multiple sensor ports for VCD, glucose, off-gas; flexible impeller configuration for shear-sensitive cells; perfusion-ready |
| AppliFlex ST single-use bioreactor for vaccines |
0.5–15 L | Clinical (cGMP) vaccine production, viral seed expansion, fast turnaround in multi-product facilities | Gamma-sterilized, fully closed disposable vessel; Click-n-Go bag loading; minimizes cross-contamination between vaccine campaigns; perfusion-ready |
| Stainless-steel bioreactors for large-scale vaccine manufacturing |
20–5000 L | Repeated commercial-scale vaccine antigen production, established viral processes, high-volume seasonal vaccines | CIP/SIP for sterile multi-batch operation; robust shear control on microcarriers; scalable design from pilot to full production; perfusion-compatible |
Detailed Process Guide for Vaccine Manufacturing
The manufacturing of vaccines is a complex, multi-step process that can vary significantly depending on the type of vaccine. Explore how the Applikon AppliFlex ST single-use bioreactor and Applikon stainless-steel bioreactors play a pivotal role in each phase.
Vaccine research and development is the initial phase where antigens that elicit an immune response are identified. This stage involves extensive laboratory research to understand the pathogen’s biology and how the immune system responds to it. The Applikon AppliFlex ST bioreactor aids in this phase by allowing for the cultivation of pathogens or cells under controlled and contained conditions, enabling the study and selection of effective antigens for the vaccine.
Once the antigens have been identified, a seed stock of the virus or bacteria is prepared. This involves growing the pathogen in controlled conditions to produce a pure and stable culture that can be used for vaccine production. The Applikon AppliFlex ST bioreactor’s precision ensures the seed stock’s optimal growth environment, maintaining the culture’s viability and purity. Thanks to the single-use approach, sterility, prevention of cross-contamination, and safety for the user are guaranteed.
The core of the vaccine manufacturing process is antigen production. This step may involve growing the pathogen for live attenuated or inactivated vaccines, or expressing the antigen in a recombinant system for subunit vaccines. The Applikon SUPR single-use production bioreactor provides a controlled environment for growing these cultures. Gamma-sterilised and easy to use thanks to the Click-n-Go bag loading, it reduces the risk of cross-contamination, protects the user from contact with the culture, and enables fast production with reduced turnaround times.
After antigen production, the next step is the isolation and purification of the antigen from the culture medium. This is crucial for ensuring the vaccine’s safety and efficacy. The Applikon SUPR bioreactor facilitates the controlled environment necessary for the growth of the culture, which is then subjected to various purification methods to isolate the antigen.
The purified antigen is then mixed with adjuvants, stabilizers, and preservatives to form the final vaccine. This formulation process is essential for enhancing the vaccine’s effectiveness and longevity. Although the Applikon bioreactors are primarily involved in earlier stages of vaccine production, the data and insights gained from their use are critical in determining the optimal conditions for vaccine formulation.
Before vaccines can be made available to the public, they must undergo rigorous clinical trials to test their safety, efficacy, and potential side effects across different population groups.
Once approved, vaccines enter large-scale production where large-scale bioreactors like the Applikon SUPR 1000 are used to meet global demands. The flexibility and scalability of these bioreactors make them ideal for adjusting production volumes based on demand. The AppliFlex ST and SUPR offer a scalable platform from 500 mL to 1000 L (from 2025), designed for both research and production, enabling a seamless transition to larger manufacturing processes and facilitating a fast response to emerging health threats.
