History of squalene use in vaccines
This fact-check may be outdated. Consider refreshing it to get the most current information.
Executive summary
Squalene has been used as the oil phase in emulsion vaccine adjuvants (not as a stand‑alone ingredient) in licensed influenza vaccines since the late 1990s in many countries and in at least one U.S. flu product for older adults (Fluad) [1] [2]. Squalene-containing emulsions such as MF59, AS03 and AF03 are widely studied and used in influenza vaccines globally and are under active research and market expansion, including shifts from shark to yeast/plant or synthetic sources [3] [4] [5].
1. What squalene is and why vaccine makers use it
Squalene is a naturally occurring lipid found in humans and many plants and animals; formulated into oil‑in‑water emulsions it acts as the oil phase that helps adjuvants boost immune responses, increasing antibody magnitude and breadth for vaccines such as seasonal and pandemic influenza [1] [3]. Scientific reviews and experimental studies describe squalene‑based emulsions—MF59, AS03, AF03—as adjuvants that amplify innate and adaptive responses and improve hemagglutinin‑specific B cell and memory responses in influenza vaccination [3].
2. Timeline and regulatory reality: When it entered vaccine practice
Squalene‑containing adjuvants were introduced into human influenza vaccines in the late 1990s in Europe; WHO notes millions of squalene‑adjuvanted flu doses administered there since 1997 with no signal of widespread serious harms [1]. In the United States, MF59‑adjuvanted Fluad was approved for people 65 and older beginning with the 2016–2017 season [2] [1]. Global use expanded again around 2009 H1N1 and in COVID era planning, where companies considered squalene adjuvants to extend antigen supply [6] [4].
3. Safety record and controversies
Public concern and activist claims have linked squalene to conditions such as Gulf War illness and alleged autoimmune harms; those claims appear in alternative‑media and advocacy pieces but are not corroborated here by the larger regulatory and scientific literature cited in these sources [7] [8] [9]. By contrast, meta‑analyses and reviews found MF59‑adjuvanted influenza vaccines had acceptable safety profiles and in some analyses showed equal or modestly better clinical outcomes than non‑adjuvanted vaccines [1] [3]. Official agencies stress that adjuvanted vaccines undergo clinical testing and post‑licensure monitoring [10].
4. Where squalene comes from — supply, ethics and market dynamics
Historically most squalene for pharmaceuticals came from shark liver oil; conservation and supply concerns have driven industry and academic efforts to replace shark‑derived squalene with plant, yeast or synthetic alternatives [11] [4]. Market reports and research show rising pharmaceutical demand and investment in non‑animal squalene (yeast‑derived, biosynthetic) and note the growing market value and forecasts into the 2020s [12] [4] [5].
5. New science and product developments
Recent peer‑reviewed and preclinical work continues to refine squalene‑emulsion mechanisms and to validate alternatives: reviews describe mechanisms for MF59/AS03, while 2023–2025 studies report yeast‑derived or semi‑synthetic terpenoids with adjuvant activity comparable to shark squalene and experimental adjuvants or formulations being evaluated [3] [13] [5]. Industry and academic teams explicitly aim to match efficacy while reducing ecological and supply risks [14] [5].
6. What reporting and advocacy get right — and where they diverge
Advocacy pieces and some online reports emphasize past military vaccine debates and allege widespread covert use or long‑term harms from squalene in anthrax or flu vaccines; such accounts appear in the provided results but are contradicted or qualified by public‑health reviews and regulatory records that document licensed uses, clinical testing and large‑scale post‑marketing surveillance without clear causal signals of mass adverse outcomes [8] [7] [1] [10]. The divergence reflects differing agendas: conservation/consumer activism focuses on source and consent; scientific and regulatory sources focus on controlled trials, epidemiology and risk–benefit balance [11] [10] [1].
7. Bottom line for readers
Squalene is an established component of several licensed influenza adjuvants used worldwide to enhance vaccine immune responses; regulatory agencies and meta‑analyses cited here report acceptable safety profiles for those formulations, while supply and ethical concerns have driven rapid development of non‑shark squalene sources and new adjuvant research [1] [3] [5] [4]. Available sources do not mention a confirmed causal link between licensed squalene‑adjuvanted vaccines and large‑scale chronic autoimmune disease outbreaks; conversely, they do document ongoing research, market growth and persistent activist scrutiny [1] [12] [8].
Limitations: this review quotes only the sources you provided and does not attempt to adjudicate clinical causation beyond what those sources report.