China's drug regulator has approved the country's first vaccine1 that can protect people from four influenza2 virus strains. 中国药品监管机构批准上市国内首支可保护人们免受四种流感病毒侵扰的疫苗。 The four-strain vaccine adds protection against the Yamagata lineage of Influenza B, which was the main virus strain during the last flu season, according to the National Drug Administration of China. Two domestic companies -- Hualan and Changsheng -- are the approved vaccine producers. The vaccine may be used on adults and children aged3 three years and above. H1N1 and H3N2 of Influenza A, and Victoria and Yamagata lineages of Influenza B are the common strains of human flu viruses. Until now, China had only three-strain vaccines4 on the market. The seasonal5 flu is an acute respiratory infection caused by influenza viruses, affecting seniors, infants, and people with cardiopulmonary diseases in particular. Vaccination6 is considered the most effective way to prevent infection and guard against an epidemic7. Last winter, north China regions battled a surge of flu infections. Child cases reportedly rose sharply, leading to crowded hospitals.