Also known as: hydrolyzed gelatin, porcine gelatin, bovine gelatin
Gelatin (Hydrolyzed)
Sourced from FDA-approved package inserts (DailyMed). Last verified: 2026-07-07.
What It Is & Why It's in Vaccines
Pharmaceutical-grade hydrolyzed gelatin is a protein derived from animal collagen (typically porcine or bovine), partially broken down into smaller peptides. It is used as a stabilizer in some live attenuated viral vaccines to protect the virus during freeze-drying (lyophilization) and storage.
Stabilizer — gelatin maintains the viability and potency of live attenuated viruses during lyophilization and reconstitution. Without a stabilizer like gelatin, freeze-dried live-virus vaccines would lose potency during storage.
Dose-in-Context
Per-Dose Quantity
14.5 mg per dose (M-M-R II), varies by product. Some products contain bovine gelatin, others porcine.
Reference Comparison
Gelatin is a food-grade protein consumed in gram quantities daily in products like Jell-O, marshmallows, gummy candies, and capsules. 14.5 mg in a vaccine represents ~0.1% of the gelatin content of a typical serving of gelatin dessert.
Source: DailyMed package insert: M-M-R II.
Route-of-Administration Note
Injected route. The principal safety consideration is not gelatin toxicity (gelatin is a food protein with negligible inherent toxicity) but potential IgE-mediated hypersensitivity in individuals with pre-existing gelatin allergy — this is a labeled contraindication.
Documented Adverse Effects
IgE-mediated anaphylaxis in individuals with gelatin allergy — this is a labeled contraindication for gelatin-containing vaccines. The estimated incidence of gelatin allergy in the general population is low (~0.01–0.1%), but individuals with known gelatin allergy (including food allergy to gelatin-containing products) should not receive gelatin-containing vaccines without specialist evaluation.
Gelatin-containing vaccines (particularly MMR, varicella, and yellow fever) have been associated with a small increased risk of allergic reactions in the immediate post-vaccination period. The absolute risk is very low (estimated ~1–3 per million doses for severe reactions in studies that have traced the reaction to gelatin specifically).
Vaccines Containing Gelatin (Hydrolyzed)
MMR — M-M-R II (Merck Sharp & Dohme LLC)
Live attenuated; no adjuvant. Product contains no preservative.
Varicella — Varivax (Merck Sharp & Dohme LLC)
Yellow Fever — YF-VAX (Sanofi Pasteur)
ⓘ Methodology Disclaimer: Ingredient lists are sourced from official FDA-approved package inserts for the specific branded products named on each vaccine page. Formulations can change between manufacturing lots and over time — always verify against the current package insert before making a clinical decision. The presence of a substance in a vaccine does not by itself indicate harm; toxicology is dose-, route-, and context-dependent. Comparisons to reference exposure levels are provided with their sources where available, and are approximate — see the cited source for full methodology.