Host cell protein risks, detection, and control in vaccine manufacturing

Host cell proteins (HCPs) are critical process-related impurities in vaccine manufacturing that can affect product safety, efficacy, and regulatory compliance. Challenges persist in detecting and controlling HCPs due to their diverse properties and interactions with vaccine components across viral vector, recombinant protein, and nucleotide vaccine platforms. This review provides a comprehensive analysis of HCP risks, detection technologies, including ELISA and advanced mass spectrometry, and control strategies encompassing upstream cell line engineering and downstream purification processes. Regulatory expectations from global authorities are discussed, emphasizing risk-based, case-by-case specification setting rather than universal numeric limits. The review further explores the operational and analytical challenges faced by manufacturers, particularly in low- and middle-income countries, and advocates for harmonized guidelines and decentralized analytical capacity to support rapid, equitable vaccine deployment. By integrating risk-informed control strategies, advanced analytics, and lifecycle monitoring, the field can ensure robust vaccine production and global access, supporting both pandemic preparedness and long-term public health.

Host cell proteins (HCPs) are critical process-related impurities in vaccine manufacturing that vary by platform, persist despite purification, and carry product-specific safety and regulatory implications – yet no universal numeric limit exists, requiring risk-based, case-by-case control strategies aligned with ICH principles.

What you will learn

01

How HCP risk profiles differ across viral vector, recombinant protein, and RNA vaccine platforms

02

How ELISA, mass spectrometry, and orthogonal methods detect and characterise HCPs throughout manufacturing

03

How upstream cell line engineering, downstream purification, and lifecycle monitoring form a complete HCP control strategy

HCP risk-to-control pathway

1

Risk characterisation by platform & HCP class

2

Detection via ELISA & orthogonal analytics (LC-MS/MS)

3

Upstream & downstream clearance strategies

4

Lifecycle trending & risk-based specification setting

Key findings

HCP risk is highly platform-specific – proteases, chaperones, and cytokine-like proteins are among the highest-risk species, while some residual HCPs may provide adjuvant-like benefits; risk must be evaluated per product, dose, and route of administration

ELISA remains the release workhorse but cannot identify individual HCP species; LC-MS/MS and antibody affinity extraction (AAE) provide deeper characterisation and are increasingly expected by regulators as orthogonal evidence, particularly for persistent or product-interacting HCPs

No universal HCP limit applies across vaccine modalities – licensed products range from ≤40 ng/dose (insect cell-derived) to ≤400 ng/dose (adenoviral vector), with RNA vaccines typically requiring HCPs below the limit of quantification; specifications must be justified case-by-case

LMIC manufacturers face disproportionate analytical barriers – harmonised, risk-based guidelines and decentralised analytical capacity are essential for equitable vaccine production and rapid pandemic response, consistent with CEPI's 100 Days Mission

Key interests

Host Cell Proteins

Vaccine Manufacturing

Process Impurities

Mass Spectrometry

ELISA

QC & CMC

Regulatory Compliance

Global Health Equity