Production Process of Influenza A (H1N1) Vaccine

The production of a single batch of vaccine needs to go through the steps of virus inoculation, virus culture, virus inactivation, purification, lysis, proportioning, packaging and batch issuance before it can finally be put into use.

With the strong support of the National Influenza A (H1N1) Prevention and Control Protection Group, the General Administration of Customs and the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China (AQSIQ), the influenza A (H1N1) vaccine strain NYMCX-179A from the U.S. CDC was sent to Beijing Coxin in the evening of June 8, 2012, which was the first batch of influenza A vaccine in the world. After getting the strain, Beijing Kexing quickly started the preparation of the seed batch of the strain.

①Pre-production Preparation

A. Strictly selecting specific chicken embryos for influenza vaccine production requires the preparation of a large number of 9-11 days old chicken embryos. Chicken embryos come from Hyland's white chickens and are supplied by a specialized company. The first step is to screen the chicken embryo suppliers and conduct a quality audit. Chicken embryos have low or no resistance, and the injected influenza virus is not killed by the embryo's own resistance. Chicken embryos have white shells with good light transmission, and under the illumination of a darkroom light source, you can clearly see the blood vessels, etc. in the chicken embryos, which makes it easy to weed out weak and dead embryos.

Each batch of chicken embryo sent over to the strict screening. External inspection***4 items: white shell, size, broken and dirty embryo, internal inspection***9 items: remove sandy shell, deviated gas chamber, free gas chamber, inverted embryo, spermless egg, terminated embryo, weak embryo, contaminated embryo, cracked embryo.

B. Virus strains need to be amplified to meet production needs

The virus seed sent by WHO is the original seed of recombinant virus strains, which retains the antigenicity and replication ability of the virus, and reduces the viral pathogenicity. However, the amount is relatively small, not enough for mass production of vaccines, which must be diluted, amplified and cultured to prepare virus seed batches, and to verify the amplification data, such as the dilution to what concentration of culture is better.

After the virus seed is diluted, it is planted into the allantoic cavity of the chicken embryo (equivalent to the amniotic fluid of a human embryo), which is then placed in an airtight, aseptic, constant-temperature incubator to allow the virus to multiply rapidly. After the chicken embryos have been cultured for a certain period of time, the fluid in the allantoic cavity is extracted, and then the culture is repeated to obtain a suitable generation of viral seed, which is retained to become the seed lot for vaccine production.

②Mass production

The production process is not exactly the same in each company but the general route is similar.

A, large-scale culture to obtain a large number of viruses

The production of vaccines can reach tens of thousands of chicken embryos at a time, the process of large-scale cultivation and harvesting of viruses is the same as obtaining viruses for the seed batch, except that it is a purely mechanized operation, which reduces the manual contamination and improves the efficiency of production.

B, virus inactivation, to remove the pathogenicity

WHO provided to the vaccine manufacturers of the virus, although the infectivity is very low, but because it is still a live virus, so it is also necessary to produce the virus inactivation treatment to remove the pathogenicity of the virus. This involves adding an inactivating agent to the virus harvesting solution and treating it for a certain period of time to obtain a virus inactivation solution. The virus inactivation solution is also subjected to an inactivation test to ensure that the vaccine has been inactivated. In addition to this, the inactivated virus is also tested for protein content, hemagglutination potency, sterility, and many other tests.

C, vaccine purification, lysis, to get high-purity liquid

Virus inactivation fluid has a lot of impurities, such as chicken embryo inside the protein, inactivation of chemical reagents, and so on, and therefore also to carry out the purification, in order to retain the virus as a vaccine as the active ingredient-antigen, and to remove the inactivation of virus in the liquid of the other impurities, in order to avoid the impurities of these adverse reactions to the human body. Adverse reactions to the human body. After the inactivation solution is concentrated by ultrafiltration, it is then purified several times by physical methods such as chromatography, filtration, centrifugation, etc. After that, lysate is added to make the virus lysed, and the vaccine purified solution is obtained by further purification to remove the lysate and the heterogeneous proteins, and then sterilized and filtered to obtain a high-purity vaccine stock solution finally.

After the inactivation and lysis steps, the influenza A virus is no longer a live virus, but an incomplete virus that does not cause infection. So the rumor that the outbreak of influenza A in Beijing's primary and secondary schools was due to the vaccination before the National Day is unscientific.

D, proportioning and filling to obtain the finished vaccine

After the antigen is purified, it needs to be diluted to the right concentration by adding buffer to the vaccine stock solution. Sometimes, in order to reduce the amount of antigen and relatively expand the yield of vaccine, it is also necessary to add appropriate adjuvant for proportioning. Vaccines with added adjuvants help stimulate the body to produce an immune response more than unadjuvanted vaccines, so the amount of antigen needed per vaccine is much less. This is followed by filling into the finished vaccine.

③Vaccine testing to determine effectiveness and safety

After the vaccine is produced, the company has to sample the finished product to determine its effectiveness and safety, and then send it to the China National Institute of Pharmaceutical and Biological Products (CNIPBP) for testing, and it can be put into use only if it receives a certificate of conformity for the batch issuance of the vaccine. In order to shorten the time as much as possible, the China National Institute for the Control of Pharmaceutical and Biological Products has decided to launch a synchronized batch issuance. The two sides will be inspected at the same time, mainly for sterility, pH value, inactivator residue, abnormal toxicity, bacterial endotoxin content, adjuvant content and vaccine efficacy.