The H7N9 Cipher

In April, egg trucks started heading for Ad­im­mune Corporation’s vaccine plant in ­Tanzi, Tai­chung, delivering a batch every other day, each batch containing 260,000–290,000 specially produced eggs. In the normal run of things, these eggs should all be used to make 10 million doses of seasonal human flu vaccine this year.

But their actual fate depends on the development of the H7N9 avian flu.

The first H7N9 avian flu infection was detected in mainland China in February. In late April, Taiwan saw its first case, which originated from the mainland. Though the outbreak on the mainland is currently on the decline, Taiwan is ready to launch a vaccination program if human-to-human transmission of the virus should begin. And Adimmune states that the eggs are ready and production of H7N9 vaccine can begin immediately upon delivery of the vaccine strain.

After solutions of cultured virus are collected, they undergo purification and viral inactivation processes.

Adimmune, its NT$3-billion plant designed and built to PIC/S GMP standards, boasts Taiwan’s only human vaccine production facility. Its first task after it opened in 2009 was to manufacture vaccine for the Type A (H1N1) novel flu, competing with international pharmaceutical giants Novartis and CSL in research, development and production.

This campaign against H1N1 was Adimmune’s first independently completed, start-to-finish flu vaccine manufacturing task after being retooled and upgraded from being a contract packager of flu vaccine solution. Since then, Adimmune has been producing seasonal flu vaccines yearly according to the WHO’s recommendations for virus strain selection, making it a major source for purchases by the Centers for Disease Control. It is also taking part in a joint vaccine solution manufacturing program with the world’s sixth-largest flu vaccine company, the Dutch firm Crucell.

So the outbreak of H7N9 is not first time that Adimmune has battled a flu virus with the potential to spread worldwide. But what makes it different from H1N1 is that H7N9 is currently still an avian flu virus.

Liu Chung-cheng, president of Adimmune and former head of the Industrial Technology Research Institute’s Institute of Biomedical Sciences, says the company is already preparing for the possibility of H7N9 becoming a human-to-human transmitted virus. To this end, Adimmune requested vaccine strains from the International Federation of Pharmaceutical Manufacturers & Associations (IFPMA), which has a cooperative relationship with the WHO, ordering not just H7N9, but also H7N7 for use in “mock-up” vaccine studies.

The key to the flu virus’s ability to invade living cells lies in the antigenic hemagglutinin (HA) on the surface of the virus; the H7 of H7N9 is an example of this. There have been three H7 viruses on record that have infected humans: H7N2, H7N3 and H7N7. To get a handle on the habits of this all-new H7N9 virus, the world’s virologists and drug manufacturers first need to understand the other H7 flu viruses.

According to an article in The Economist, studies by American researchers indicate that the antigens of the other H7 viruses are unable to trigger sufficient immunoreactions. Addressing this, Academia Sinica Institute of Biomedical Sciences research fellow Ho Mei-shang says this doesn’t mean other H7 viruses are useless. Liu Chung-cheng notes that when using H7N7 to test what conditions can induce better immunoreactions, even if it’s impossible to apply it fully to H7N9, “It’s best to rehearse so we can take the stage when the ‘real actor’ shows up.”

The attenuated H7N7 vaccine strain was sent to Adimmune’s vaccine lab in early May. The pre-battle maneuvers have begun.

To prepare a vaccine, the flu virus is first attenuated to create a vaccine strain; then an automated technique is applied to inoculate fertilized eggs.

The “real actor” Liu is talking about is the H7N9 vaccine strain. Liu says that the company will receive the vaccine strain from the US Centers for Disease Control in early June, and production will begin July at the soonest.

The production method for H7N9 vaccine “is no different from that of other flu vaccines,” says Liu. Ad­im­mune cultures the flu virus in chicken embryos: one egg can produce around 1 billion individual viruses, and from an average batch of 260,000 eggs, 200,000 doses of vaccine can be made.

The eggs Adimmune is using to produce seasonal flu vaccines were in fact ordered last summer. Liu says he certainly doesn’t want for H7N9 to be transmitted person to person, but if that were to happen, “We’re ready. The eggs used for making other vaccines can be switched over to make H7N9 vaccine at any time.”

Beyond Adimmune’s production readiness, an article in The Economist states that the WHO has supplied grant funding to flu vaccine production facilities in 14 countries for research, development and production. Work is underway in four of them, including Novartis, which has informed the media about its progress.

In fact, whether the WHO and pharmaceutical companies worldwide can immediately start H7N9 vaccine production hinges not only on whether the disease attains the capacity for human-to-human transmission, but also on concerns of viral mutation. In early April, David Heymann, American epidemiologist and former official of the WHO, stated in an interview with international media that it would have been inadvisable to begin vaccine production too early, given the progress of the outbreak at the time.

The epidemic quickly stabilized in May following the closing of live poultry markets in the Shang­hai region and the warming of the weather. Ho Mei-­shang predicts that there won’t be another wave of this flu before the fall and winter seasons.

As Taiwan’s sole human vaccine producer, Ad­im­mune has a designated production schedule for seasonal flu vaccine. At this point, even after the company receives the vaccine strain for the H7N9 virus, it won’t begin mass production of H7N9 vaccine without a procurement contract from the CDC, given the limited number of eggs it has.

Taiwan now depends on Ad­im­mune’s vaccine production capacity of 10 million doses a year to react to any possible flu outbreak. The DOH is concerned about egg sourcing in the event of mass bird deaths caused by a repeat of the H5N1 avian flu scenario. So the company decided to start researching the cell culture method as an alternative to egg-based vaccine production.

The National Health Research Institutes (NHRI) is Taiwan’s sole organization with the technology to produce flu vaccines using the cell culture method, culturing antigens with Madin-Darby Canine Kidney (MDCK) cells. The NHRI has requested H7N9 vaccine strains from the US Centers for Disease Control and Japan’s National Institute of Infectious Disease, and expects to receive them in June.

Su Ih-jen, director of the NHRI’s National Institute of Infectious Diseases and Vaccinology, notes that cell culture is a more advanced approach: “During avian flu epidemics, there are often mass slaughters of chickens. Without chickens, there are no eggs, so how can we make vaccines?”

Says Huang Li-min, director of National Taiwan University Hospital’s Division of Infectious Disease and convener of the DOH’s Advisory Committee for Immunization Practices, “The flu virus is quite special: it grows well in chicken embryos, but this is an old technology; vaccines for numerous diseases like rubella and mumps are produced by the cell culture method.” He believes that with the advancement of cell culture technology, there are bright prospects in applying it to flu vaccines.

But Ho Mei-shang worries that given Taiwan’s limited clinical vaccine testing resources, if a flu epidemic breaks out and vaccine needs to be produced quickly, it may be very difficult to integrate resources effectively if vaccines are being made in two different ways.

Moreover, the US government has previously provided funding to a number of international pharmaceutical companies to develop flu vaccine with the cell culture method. However, some of the companies have decided to give up. In light of this, Ho says that we should keep in mind the failures of these overseas pharma giants. In the face of a global epidemic, Taiwan shouldn’t be setting off down this pointless path.

Though Ad­im­mune develops other vaccines using the cell culture technique, it still produces flu vaccine via the embryo method. Company president Liu Chung-cheng says that with 260,000 eggs producing 200,000 vaccine doses, Ad­im­mune would need at least 2,000 liters of cell culture solution to attain an equivalent production capacity; such a production rate is less efficient the embryo technique.

In addition, the embryo method is more scalable, able to be adapted to changes in the size of the epidemic. The cell culture production technique, on the other hand, is somewhat inflexible. “Ninety percent of the world’s flu vaccine is still made using the traditional egg embryo method,” says Liu.

Vincent Racaniello, professor of microbiology and immunology at Columbia University, has repeatedly appealed to the US government to support the development of a totally new flu vaccine production method besides the chicken embryo and cell culture techniques. Ho Mei-shang suggests that making subunit vaccines (using selected viral proteins rather than the whole virus) is a possible future course that Taiwan’s government can consider developing toward.

Once the flu breaks out, the availability of vaccine is a matter of national security. Companies are happy to work with the government as long as the government guarantees purchases.

On the other hand, if the government is concerned about waste stemming from advance purchase and stockpiling of vaccine, and doesn’t have the resolve to treat the expenses of vaccine purchase as a sunk cost, then companies won’t be willing to take the risk of going into mass production.

In sum, when to start making H7N9 vaccines and how much to make are questions of timing as well as issues that challenge decision making.

“The flu virus is really tricky,” says Liu. In dealing with this virus, both vaccine manufacturers and government disease control decision-makers face a dilemma.