Status: "mock-up approval" in European Union in 2008; being distributed for the 2009/10 flu season by various European and other countries

Organizations involved:

Baxter AG – Manuf.; R&D; Tech.

GlaxoSmithKline plc – Parent

Baxter Healthcare Corp. – Parent; World mark. [sales to governments]

Cross ref.: See the Influenza H1N1 Vaccine Products and Influenza Vaccine Products entries. Note, there is also an analogous H5N1 (bird, not swine, flu) vaccine, called Celvapan H5N1 (see related entry).

Description: Celvapan is a monovalent whole virion H1N1 influenza vaccine containing inactivated wild-type influenza A/California/07/2009 (H1N1) virus cultured in Vero cells, a continuous African green monkey kidney cell line. The vaccine contains 7.5 µg/dose of Hemagglutinin (HA) per dose. The whole virions of Influenza type A, the active ingredient, are inactivated both by formaldehyde and UV-irradiation and purified on a sucrose density gradient.

Excipients in Celvapan are polysorbate 80 (Tween 80), 0.10-0.15 % (target 0.125 % i.e. 0.63 mg/dose); Tris-buffered Saline with sodium content of 4.0 mg and tris (Trometamol) content of 1.2 mg; and Water for Injection (filled to 0.5 mL). Tween 80 prevents re-aggregation of the virions. Trypsin (presumably to dissociate Vero cells for culture) and Cytodex (microcarrier beads for the adherent Vero cells) are also used in the manufacturing process, and both are from animal sources. These were evaluated and found to present no risk of TSE transmission. Benzonase, as nuclease (breaks down nucleic acids) is also used in manufacture. Biological reagents involved in routine manufacture of the active substance do not contain components of bovine origin. No materials of animal origin are added to the Active Substance in the manufacture of the finished product.

Celvapan is packaged in 10-dose glass vials containing 7.5 microgram hemagglutin/0.5 ml dose with no preservatives. Due to the general growth characteristics of the A/California/07/2009 (H1N1)v virus strain, i.e., difficulties in its culture, the specification for HA content of the drug substance has been adjusted to be not less than 40 µg/mL. Overfilling of the vials by 0.85 mL minimum ensures that the 10 doses/vial can be drawn from the vial, with the 10 dose vials containing at least 5.85 mL of inactivated influenza virus in solution.

Companies.: Baxter produces bulk H1N1 vaccine at its large-scale facility in Bohumil, Czech Republic (also reported as Baxter BioScience s.r.o. in Kostelec nad Cernymi lesy, Czech Republic), and ships the vaccine to Vienna, Austria for final formulation, fill and finish before distribution.

Manufacture: The manufacturing process using the Vero cell technology can be divided into four main stages: Vero Cell Propagation; Virus Propagation and Harvesting; Inactivation and; Purification and sterile Filtration. In the upstream processing, cells are produced and then infected with the respective influenza virus. Then the virus is harvested and inactivated by sequential formaldehyde and Ultraviolet Irradiation (UV) inactivation steps. These two steps were designed for two separate targets i.e. primarily protein for formaldehyde and nucleic acid as a target for UV irradiation. In Purification I, the product is concentrated and purified using ultracentrifugation with a sucrose gradient. During Purification II, the product is homogenized and sucrose and further impurities are removed by ultrafiltration. The final stage of Active Substance manufacture is the sterile filtration of the Monovalent Bulk.

Quality control testing is performed on intermediate products at the following steps: Vero cell culture in Fermenter prior to infection; Fermentation Broth; Formaldehyde Treated Virus Harvest; and Purified Monovalent Virus Harvest (PMVH) as the result of Purification I.

Process validation studies for Celvapan were based on the H5N1 Influenza strains A/Vietnam/1203/2004 and A/Indonesia/05/2005. The validation of Active Substance manufacture was carried out with the Vietnam/1203/2004 strain. The occurrence of human infections with Clade 2 H5N1 influenza strains in Indonesia, and the high mortality rate (56%) associated with these infections, prompted Baxter to also produce a whole virus H5N1 influenza candidate vaccine based on the Clade 2 A/Indonesia/05/2005 strain for a clinical Phase 1 study, which was used to validate the formulation and filling process steps.

Process validation of the Vero Cell Inoculum in Bohumil included 12 consecutive lots. The conformity of the cell propagation from 120 L up to 6,000 L bioreactors was tested on 3 consecutive lots for the purpose of the Process Validation of the Cell Propagation at different stages of Fermentation. These results showed that different lots used for both the Vero cell inoculation and fermentation process were found to be comparable. The strain used for process validation covering virus propagation, harvest and inactivation was A/Vietnam/1203/2004 (Clade 1). Three conformance lots were produced in the Bohumil facility and the results confirmed the consistency of the manufacturing process. During the process validation for Celvapan production, it was verified that the manufacturing process of the virus propagation, harvest and inactivation, purification and transport conformed to the process validation protocols.

Product- and process-related impurities identified during the Active Substance manufacturing process and routinely tested during manufacture are Vero Cell DNA during Manufacturing of Monovalent Bulk (MVB); Residual Vero Cell DNA in the Monovalent Bulk; Vero Host Cell Protein; residuals of formaldehyde, sucrose, trypsin and B senzonase.

The genetic stability of the influenza virus grown in Vero cells versus egg-derived virus was evaluated by comparing the genetic sequence of the hemagglutinin gene sequence of an egg-derived Seed Virus Bank to that of a Post Production Virus developed in Vero cells. The two were identical on the DNA and on the amino acid level, demonstrating that once a recommended vaccine strain had been adapted to sufficient growth in eggs, no re-adaptation during the passages in serum-free Vero cells occurs.

The specifications for the monovalent bulk include a test for Vero cell protein via ELISA, Hemagglutinin assay and single radial immunodiffusion (SRD) test for HA protein, the Bradford Method for total protein, the Hemagglutination Inhibition (HI) test, H1N1 identity test using RT PCR, a safety test for preparative influenza virus on Vero cells, a test for Tween 80 concentration via photometric detection, the LAL test for bacterial endotoxin and a sterility test.

Sterile Monovalent Bulks (MVB) are transported at 2-8 °C from the Bohumil facility in the Czech Republic to Vienna/Austria for formulation. Tris-buffer and Tween 80 solution are delivered from the company's Orth, Austria, facility. The calculated amount of Tween 80 solution and Tris-Buffer are sterile filtered into the formulation tank. No preservatives are added. The mobile tank is stored at 2-8 °C until filling. The Bulk Medicinal product is filled under clean room Class A conditions (EU cGMP Guide) in multi dose vials and the vials are stoppered and crimped under class A conditions to give the Final Container Product.

To overcome possible limitations of availability of a single radial immunodiffusion (SRD) test for HA protein reagents during a pandemic situation, Baxter developed an alternative hemagglutinin (HA) quantification method based on HPLC determination of the HA-1 subunit of the HA protein.

Baxter received the 2009 H1N1 strain for testing and evaluation from the Centers for Disease Control and Prevention (a WHO Collaborating Center) in early May 2008. Baxter then undertook pre-production testing and evaluation of the virus strain to assess its growth characteristics in the company's proprietary Vero cell culture technology. Baxter initiated commercial production in early June, and made its first commercial product within 12 weeks of receipt of the virus. Baxter completed production of the first batches of vaccine in late July and initiated its first delivery within two weeks. Subsequently, Baxter continued to deliver vaccine on an ongoing basis to national public health authorities having ordered the vaccine.

Status: Various governments, particularly in Europe, have ordered and will distribute this vaccine.

On Jan. 30, 2009, Baxter submitted a MAA seeking full approval of Celvapan containing A/Vietnam/1203/2004 (H5N1) under exceptional circumstances as an H5N1 mock-up pandemic influenza virus vaccine, through the centralised procedure under Article 3 (2) (a) of Regulation (EC) No 726/2004.

On Sept. 22, 2009, Baxter applied for a variation to change the strain used for manufacture to A/California/07/2009 (H1N1)v.      

On Oct. 9, 2008, the EMEA/EU granted mock-up licensure for Celvaplan (approved the variation), based on clinical and other studies with a different strain with pandemic potential. This approval was for 7.5µg of HA antigen of strain A/Vietnam/1203/2004 (or A/Indonesia/05/2005) per 0.5 ml dose presented in a 10-dose vial with no preservative added. The vaccine had been tested in five completed clinical trials worldwide in more than 1,300 people. In addition, more than 3,500 people had been vaccinated using the same strain during a then ongoing Phase III study.

Mock-up licensure is a regulatory pathway for pandemic vaccines that was created by the EMEA/EU in 2004. Such EU mock approvals allow for the development, evaluation and licensure of a company's pandemic candidate vaccine using an available influenza strain that has the potential to cause a pandemic. Once a pandemic is declared and the influenza virus strain causing the pandemic is identified, the mock-up licensure allows for fast track approval of a pandemic vaccine containing the actual pandemic strain. The mock-up/core dossier approach allows for insertion of the pandemic strain into a vaccine construct based on all the data obtained with the corresponding mock-up vaccine together with specific data relating to the pandemic strain. This is based on the premise that the final pandemic vaccine is produced in the same way (i.e., with regards to the formulation, manufacturing process and control methods) as approved for the mock-up vaccine. Therefore, the strain change variation application (MAA) contains mainly the quality data that are new and relevant for the pandemic influenza vaccine virus.

Celvaplan was the first cell culture-based and non-adjuvanted pandemic influenza vaccine to receive marketing authorization in the European Union.

Celvapan is based on a new strain, A/California/7/2009 (H1N1)v, and complies with the WHO3 and CHMP4 recommendations for the emergent novel H1N1 influenza vaccine composition. In support of the strain change to A/California/07/2009 (H1N1)v, Baxter submitted quality data in accordance with the quality requirements for a novel influenza H1N1 vaccine, the Guideline On Dossier Structure And Content For Pandemic Influenza Vaccine Marketing Authorisation (CPMP/VEG/4717/03 Rev. 1) and EMEA fast track procedure for community human influenza inactivated vaccines annual strain(s) (CHMP/BWP/99698/07). The same manufacturing process, with the exception of strain-dependent parameter, and safety precautions were applied to production, including the release and shelf-life specifications.

Baxter will supplement its licensure post-approval with data from its ongoing clinical trial program.

Trials: In fall 2009, Baxter was conducting two randomized trials in 400 healthy adults age 18 and over and in 400 children and adolescents to supplement the licensure post-approval with appropriate clinical data. These trials were evaluating the safety and immunogenicity of the vaccine at dose levels of 7.5µg and 3.75µg. Once countries initiate national vaccination programs using CELVAPAN H1N1, Baxter will also conduct a large-scale observational study with CELVAPAN in 9,000 people of different age groups, including children.

Preliminary safety data in adults age 18 and older indicate the vaccine is well tolerated. The observed systemic and local reactions are similar to those generally experienced after vaccination with licensed seasonal influenza vaccines.

Medical: The mock-up EU licensure calls for two 7.5 µg doses of vaccine to be given 21 days apart. Baxter expects the data from the trial of healthy adults to indicate whether a single dose may be possible. This study will also determine whether a lower dose, 3.75µg, is sufficient to induce the necessary immune response.

Once countries initiate national vaccination programs using Celvaplan, Baxter will also conduct a large-scale observational study in 9,000 people of different age groups, including children.

Trials: Clinical trials began in the U.S. on August 6, 2009 (with approval about 5 weeks later).

Market: 2009 sales will primarily from sales to governments.