BEIJING, Sept. 23 (Kyodo) — Fourteen people who this week received H1N1 flu vaccinations in Beijing in China's first mass inoculations against the virus have displayed "adverse effects," state media reported Wednesday. The 14 were among 39,000 residents of the city who received the vaccines produced by Chinese pharmaceutical company Sinovec by Tuesday afternoon, Xinhua News Agency said. State broadcaster CCTV reported that the "adverse effects" included fever, headache and nausea, and developed within 24 hours of receiving the vaccinations. Some 10,000 performers and students involved in the Oct. 1 National Day parade were in the first batch on the mainland to receive the vaccinations Monday, and no side effects were reported from among them. A total of 100,000 students from schools and universities who are participating in the parade will receive the vaccines this week, state media earlier reported. Prior to the first mass inoculations this week, the country had carried out small-scale vaccinations on test groups. The vaccination program is targeted at youths and vulnerable groups in the population and was announced by the Chinese government earlier this month after it approved the vaccine produced by Sinovec. Liang Xiaofeng, director of the immunization program, was quoted by Xinhua as saying that investigations were being carried out, adding that four of the 14 cases could be "related to the vaccines." China, one of the first countries in the world to carry out large-scale vaccinations, has reported a rapid spread of H1N1 infections over recent weeks. By Monday, over 13,000 cases of H1N1 flu had been confirmed in the mainland, more than double the figure given by health authorities just two weeks earlier. The first case of the flu was reported in early May and, like the majority of the early flu cases, was "imported" from flu-hit countries. Earlier this month, Chinese Health Minister Chen Zhu warned that the country was entering a "severe phase" in the fight against the flu, with increasing incidences of mass domestic infections. The weeklong National Day holidays in a week's time present an added risk for infection, as 200 million Chinese are expected to be on the move during the holidays.