Apr 3, 2008 (CIDRAP News) – China's State Food and Drug Administration (SFDA) yesterday approved the country's first prepandemic H5N1 influenza vaccine, an inactivated whole-virus product made by Sinovac, a Beijing-based biotechnology company.
China's approval of Sinovac's Panflu vaccine marks the third H5N1 vaccine to win approval from national or international regulatory bodies. In April 2007, the US Food and Drug Administration approved a Sanofi Pasteur H5N1 vaccine. A month later, the European Union approved a mock-up pandemic flu vaccine made by Novartis (it is designed to speed vaccine production when a pandemic emerges and will not be manufactured until then).
Sinovac said its vaccine is approved only to supply China's national vaccine stockpile and will not be available for commercial sale, according to a company press release yesterday. In 2006 the company said it planned to produce 20 million doses of the vaccine over the next few years, according to a previous report. The latest information gave no production estimate.
"This vaccine is reserved for emergencies in the country and we have to get instructions on how much to produce," Liu Peicheng, Sinovac's publicity supervisor, told Reuters today.
Vaccine experts say there is no guarantee that vaccines based on current H5N1 strains will be effective if a pandemic H5N1 virus emerges, but they hope such vaccines will provide some protection and buy time while a vaccine specifically matched to the pandemic strain is developed.
The Sinovac vaccine contains an inactivated Vietnam strain of H5N1 virus and an aluminum hydroxide (alum) adjuvant. A phase 1 study of the vaccine, published in a 2006 issue of The Lancet, induced potentially protective immune responses in 78% of volunteers after two 10-microgram (mcg) doses.
In late December 2007, Sinovac in a press release reported preliminary phase 2 results for the vaccine. The trial included 402 adults (aged 18 to 60). Groups received two doses of 5, 10, or 15 mcg of the vaccine.
Each dosage induced varying degrees of immune response, but the 10- and 15-mcg dosages reached standards set by the EMEA to indicate good results for seasonal flu vaccines. Sinovac said the trial did not show any serious adverse reactions among the volunteers.
The researchers who conducted the phase 1 trial said a whole-virus vaccine offers a dose-sparing advantage, because 20% to 23% of the vaccine antigen is lost during the preparation of split-virus vaccines. However, Iain Stephenson, MD, of the Infectious Disease Unit at Leicester Royal Infirmary in Leicester, England, had said in a Lancet editorial that though whole-virus vaccines usually produce a better response than split or subunit counterparts, it is difficult for manufacturers to switch production methods. Also, he said whole-virus vaccines are linked to febrile reactions in children.
Sinovac has also completed a phase 1 trial of a split-virus H5N1 vaccine, which was found to be safe for children, adults, and elderly people, according to its December 2007 press release.
Peicheng said Sinovac is also conducting trials to see if its H5N1 vaccine yields cross-protection against other strains, including those from Indonesia, Turkey, and Anhui province in China, Reuters reported.
China has reported three H5N1 cases so far this year, all of them fatal.
Vietnam starts H5N1 vaccine trial
In other vaccine developments, Vietnamese researchers said today that clinical trials have begun for an H5N1 vaccine that the country is developing, according to a report from Reuters. The vaccine is based on a Vietnam strain of H5N1 virus.
The vaccine is being tested in 11 volunteers, all of whom are researchers, the report said. They received their second dose of the vaccine today at the National Institute of Hygiene and Epidemiology in Hanoi.
Nguyen Tuyet Nga, an epidemiologist and virologist who is leading the trial, told Reuters that the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have helped with the project, though no foreign pharmaceutical firms are involved in the study.
Subjects in the trial are receiving two injections 28 days apart, with doses ranging from 3.75 to 45 mcg, Nga said. She also told Reuters that researchers would test the vaccine at a later date to see if it offers cross-protection against other H5N1 strains. The report did not say if the Vietnamese vaccine is a split- or whole-virus product or if it contains an adjuvant.
Vietnam has reported five H5N1 cases this year, all of them fatal.
Sep 7, 2006, CIDRAP News story "Chinese report results for whole-virus H5N1 vaccine"
Apr 2 Sinovac press release
Dec 24, 2007, Sinovac press release
Oct25 to Nov 2, 2007, CIDRAP News report "The pandemic vaccine puzzle: A seven-part series on the chances for immunizing the world against pandemic flu"