BEIJING -- A vaccine to protect people against four subtypes of seasonal influenza viruses is expected to be available on the Chinese market in the second half of 2018, a health official said.

Gao Fu, director of the Chinese Center for Disease Control and Prevention (China CDC), said the upcoming vaccine would be made in China, though other four-strain vaccines have been made available on the European and American markets.

There are four common subtypes of seasonal flu viruses: H1N1 and H3N2 of Influenza A, and Victoria and Yamagata lineages of Influenza B. A four-strain vaccine protects against all four and is more effective.

But no vaccine can provide a full guarantee, Gao was quoted as saying by the Health News, a newspaper of the National Health and Family Planning Commission.

However, taking a shot, which costs a few dozen yuan, makes more economic senses than getting sick. The medical bill of a hospitalized elderly flu patient fluctuates around 14,000 yuan (about $2,187) on average, the paper said.

It quoted China CDC sources as saying that less than 2 percent of the population is vaccinated against the seasonal flu.

The World Health Organization says seasonal flu is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. Annual epidemics of influenza are estimated to result in 3 to 5 million cases of severe illness and 290,000 to 650,000 deaths worldwide.

This winter, north China regions have been battling a surge of flu infections. Child cases reportedly rose sharply, leading to crowded hospitals and limited supplies of medicine.