The CDC is preparing a new avian influenza vaccine candidate after an analysis found that a mutated strain from the ongoing outbreak in China isn't vulnerable to existing vaccines.
Through a globally shared database, the CDC found that viruses in the most recent H7N9 epidemic in China have split into two genetic lineages, the Yangtze River Delta and the Pearl River Delta, the agency reports in its Morbidity and Mortality Weekly Report. The National Health and Family Planning Commission of China (NHFPC) reported to the World Health Organization a record-high 304 cases of human H7N9 infection between Jan. 19 and Feb. 14.
Based on these new findings, experts from the WHO have recommended (PDF) that two additional H7N9 candidates be developed: one derived from a highly pathogenic virus discovered in China’s Guangdong Province and another one from a low pathogenic A/Hunan/2650/2016 virus, both within the Yangtze River Delta lineage. The CDC is currently developing a candidate based on the latter strain.
The CDC has previously worked with the WHO to develop three vaccine candidate viruses that could be used to make vaccines against the avian influenza A virus. But a preliminary antigenetic analysis found that those vaccines might not work effectively on the Yangtze lineage. What's more, about 93% of all 74 virus samples the CDC examined from this outbreak in China were from that strain.
In an interview with Infectious Disease News, Timothy M. Uyeki, M.D., a medical epidemiologist in the CDC’s Influenza Division and one of the authors of the new report, said that the bird flu viruses have a tendency to evolve.
“For pandemic planning purposes, we need to keep up with these antigenic changes and develop candidate vaccine viruses to match them,” he said, according to the publication.
This marks the fifth outbreak of the virus in China since it emerged in the country in 2013.
No H7N9 vaccine is currently available on the market, but since China has been the main battlefield against the bird flu, it is also playing a big role in the vaccine development effort. China’s FDA just approved for clinical testing four candidates developed by Beijing Tiantan Biological. The company’s biggest shareholder is state-owned Sinopharm.
In November 2015, China’s Hualan Bio became the first to start testing H7N9 vaccines on humans, and the company has already moved (Chinese) its two candidates—a split virion one and an inactivated one—into phase 2. The company was the first influenza vaccine manufacturer in China to get onto the WHO prequalification approval list.
Even though China is the most affected by the virus, the U.S. is also under threat. On Sunday, federal officials identified this year’s first outbreak of the avian flu in the U.S. among a chicken flock at a Tyson Foods-contracted farm in southern Tennessee. The Department of Agriculture has yet to determine the strain found at that farm.
Infection of the virus could trigger serious illness, including severe pneumonia. In January alone, the virus has caused 79 deaths in China, and the CDC estimated that about 40% of reported human cases so far have resulted in death.