Avian Influenza Vaccine Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions is issued as a clarified, inactivated, concentrated whole-virus antigen fraction for downstream formulation into multiple veterinary vaccine presentations. The bulk antigen code is structured as AIV-VG-[subtype]-API-[concentration factor]; a representative release specification is AIV-VG-H5/H7-API-50. The liquid bulk is standardised to 512–1024 HAU per 0.1 mL in isotonic phosphate-buffered saline at pH 7.2 ± 0.2, with total protein controlled at ≤0.35 mg/mL after 100 kDa tangential-flow ultrafiltration. Sterility is evaluated by membrane filtration according to USP <71> and Ph. Eur. 2.6.1. Endotoxin is limited to ≤0.25 EU per dose-equivalent by Ph. Eur. 2.6.14. Residual moisture in the lyophilised cake does not exceed 2.0 % w/w by USP <921> Method Ic. The API is preserved in a 0.22 µm filtered, preservative-free state; it is suitable for inclusion in oil-adjuvanted injectable emulsions, delayed-release oral capsules, direct-compression tablets, freeze-dried powders, fluid-bed granules, and drinking-water solutions. The multi-format processing route distinguishes this product from monovalent liquid-only vaccines because the same antigen batch can be split into injectable and oral presentations after concentration without re-inactivation or re-purification.

On a 500 L egg-fluid harvest line, continuous-flow disc-stack centrifugation at 11,500×g equivalent and 120 L/h throughput removes most of the allantoic debris and host-cell material before inactivation. The clarified fraction is inactivated with binary ethylenimine at 37 °C for 24 h under pH-stat control at pH 7.4. This inactivation route is preferred over formaldehyde-only treatment because it produces less cross-linking of haemagglutinin spikes, preserving haemagglutination titre after freeze-drying and wet granulation. Inactivation is stopped with 0.1 M sodium thiosulfate, and the bulk is then concentrated on regenerated cellulose cassettes with a 100 kDa molecular-weight cut-off and a shear rate of 3,500–4,500 s⁻¹. The concentrated retentate is diafiltered against 10 volumes of isotonic phosphate buffer to remove low-molecular-weight residuals and to improve osmolality control for subsequent formulation. Published data for this specific antigen configuration are limited; the stated process ranges reflect comparable egg-derived influenza virus clarification and ultrafiltration operations.

What release tests keep the solid oral formats from losing seroconversion activity?

Release of tablet-grade and capsule-grade API includes a panel of tests that extend beyond injectable-grade specifications. The lyophilised powder is compacted on a rotary tablet press operating at ≤8 kN compression force and 5–15 rpm turret speed; post-compression haemagglutination titre is compared with the pre-compression titre to verify ≤0.5 log2 loss. Disintegration is assessed according to USP <701> with 0.1 M hydrochloric acid for the acid-protection stage and phosphate buffer at pH 6.8 for the intestinal-release stage. Delayed-release dissolution uses USP <711> Apparatus II with 50 rpm paddle speed. The protective matrix contains 5 % w/w trehalose dihydrate, 1 % w/w sodium glutamate, and 0.5 % w/w polyvinylpyrrolidone K30 as a low-moisture binder. This matrix has demonstrated ≥95 % haemagglutination unit recovery after lyophilisation in pilot batches; however, published data for the identical formulation are limited, and batch-specific confirmation is required.

When a lyophilised premix requires cold-chain deviation tolerances

Powder and granule premix formats are dried to ≤2.5 % w/w residual moisture and packaged in double-layer aluminium foil with a moisture vapour transmission rate of ≤0.1 g/m²/day. Storage instructions require 2–8 °C; short-term sealed-pouch exposure can be tolerated up to 25 °C for 30 days based on VICH GL18 stability protocols. Open-container handling at ambient humidity is limited to 4 h at 25 °C / 60 % RH. The granulated form is produced by low-shear wet granulation in a fluid-bed dryer with inlet air at 45–55 °C and exhaust relative humidity ≤30 %. The primary incompatibility is with amine-based enteric polymers in aqueous granulation fluids; free amino groups accelerate destabilisation of haemagglutinin spikes at pH >8.0. Poly(methacrylic acid-co-ethyl acrylate) dispersions are therefore used in preference to aminoalkyl methacrylate copolymers when delayed-release granules are manufactured.

Drinking-water solutions are prepared by diluting the injectable-grade liquid API into a separate pre-mix tank before in-line proportioner delivery. The diluted vaccine remains stable for 6 h at 25 °C when protected with 0.2 % w/v skimmed-milk powder and held at pH 6.8–7.4. Chlorine-based disinfectants at free residual chlorine concentrations above 1 ppm reduce haemagglutination titre; chlorinated water must be neutralised with 0.1 % w/v sodium thiosulfate before vaccine addition. Hard water above 300 mg/L calcium carbonate can alter emulsion stability in adjuvant-containing solutions; therefore, premix preparation should avoid simultaneous addition of oil-based injectable adjuvants to drinking water. Final formulated vaccine potency in chickens is verified by haemagglutination inhibition serology and by challenge with a homologous H5/H7 virus according to WOAH Terrestrial Manual Chapter 3.3.4; a positive serological response is recorded when geometric mean HI titre reaches at least 4 log2 in vaccinated groups.

Differences in residual moisture and particle-size distribution distinguish tablet-grade from injectable-grade API

Tablet-grade and injectable-grade API are differentiated by residual moisture, particle-size distribution, and bioburden control. The injectable liquid is not spray-dried and therefore has no measurable dry particle-size specification; the lyophilised tablet-grade API is milled and sieved through a 150 µm screen, while the premix granule is retained between 150 µm and 710 µm. Bulk density of the granule fraction is adjusted to 0.48–0.60 g/mL by controlling moisture and binder addition; angle of repose remains below 35°, permitting uniform metering in auger-type premix blenders.

A further operational difference in the oral solid formats is the control of electrostatic charge. Fine vaccine powders with particle sizes below 50 µm tend to adhere to mixing equipment and segregate during feed-mill blending; therefore, the granule fraction is deliberately shifted above 150 µm while retaining a D90 ≤710 µm cut. The injectable-grade liquid avoids these dry-powder handling constraints but requires cold-chain storage and aseptic filling. The same antigen batch can be allocated to both formats after concentration, but the lyophilised and granulated portions must be separately dried under lyoprotectant or granulating excipient control to prevent haemagglutinin collapse.

Solvent-free granulation for flock-level premix administration

Fluid-bed agglomeration is used to convert the lyophilised powder into a dust-controlled premix granule. The powder is charged into a fluid-bed processor with a 0.4 m² bottom-spray insert; a binder solution of 2 % w/w hydroxypropyl methylcellulose in water is sprayed at 10 g/min per kg of solids, with inlet air at 50 °C and exhaust relative humidity ≤30 %. The process is stopped when granule moisture reaches 2.0–2.5 % w/w, and the dry granules are passed through a 710 µm sieve. This low-temperature drying avoids the destructive outlet temperatures above 80 °C that can occur in direct spray drying of antigen-containing solutions. In final feed premixes, the granule is diluted into a corn-matrix carrier with 0.5 % w/w colloidal silicon dioxide as a flow aid; quantitative metering trials in auger-type blenders show ≤5 % coefficient of variation at 1 kg/tonne inclusion rate. Published data for this specific configuration are limited, so the metering tolerance should be confirmed in the target feed-mill geometry.

Oil-adjuvanted emulsion formulation is constrained by droplet size and antigen contact time

For injectable presentations, the liquid API is combined with a mineral-oil-based adjuvant or a ready-to-use oil-in-water emulsion using a high-shear mixer at 3,000–6,000 rpm for 5–15 min. The final emulsion is targeted to a mean droplet size of 1–3 µm by laser diffraction according to ISO 13320; droplets below 0.5 µm can increase local reactogenicity in birds, while droplets above 10 µm reduce antigen release. Emulsification time beyond 20 min at 6,000 rpm is avoided because prolonged high shear at the aqueous-oil interface denatures haemagglutinin; post-emulsification HAU recovery is tested to remain ≥90 % of the pre-emulsion value. Injection volume is typically 0.2–0.5 mL depending on bird age and breed; the final formulated product is administered intramuscularly or subcutaneously. The API itself does not contain preservative or adjuvant; these are added by the downstream manufacturer because preservative selection depends on the target bird species and withdrawal-period requirements.

Compared with subunit haemagglutinin APIs produced in insect-cell or mammalian-expression systems, this egg-derived whole-virus antigen retains native surface glycoprotein density and is standardised by haemagglutination titre rather than antigen mass alone. Subunit products may have lower endotoxin risk and simpler sterility validation but generally require stronger adjuvants and may not be adapted to acid-sensitive oral delivery without encapsulation. Recombinant haemagglutinin APIs also lack neuraminidase and internal viral proteins; these internal components can contribute to cellular immune responses and may support broader protection in challenge models, although published data for this specific multi-format avian influenza vaccine API are limited. The whole-virus preparation is more sensitive to high pH and amine-containing excipients than subunit antigens, so enteric coatings and low-amine binders are mandatory for oral tablets and capsules. In contrast, the multivalent H5/H7/H9 antigen pool can be used in emergency vaccination programs where subtype coverage is required across multiple poultry compartments.

For hatchery spray and direct oral drench applications, the solution-grade API is diluted in cold sterile diluent and used within 2 h when spray equipment generates droplets 80–120 µm; smaller droplets can be inhaled rather than ingested and may reduce oral exposure. The liquid solution is not recommended for combination with chlorine-based drinking-water sanitisers or with highly buffered acidifiers that push final pH below 5.5. These operational boundaries apply specifically to the whole-virus antigen because the haemagglutinin trimer dissociates under acidic conditions and cannot be reassembled without loss of potency. No additional downstream processing steps are required beyond the target dosage-form preparation.