Another seven pupils from a primary school in Guangdong province were diagnosed with A/H1N1 influenza, according to a report from the provincial health department released on June 22.

As of June 22, the number of students from Shipai Township's central primary school in Dongguan city confirmed to have contracted the flu had climbed to 37.

China's Ministry of Health (MOH) and local health authorities are yet to disclose the origin of the infections. However, the MOH and Ministry of Education jointly issued a provisional circular on June 22 that directed school at all levels to respond to the outbreak.

According to the circular, all schools are required to check the temperature of their students and report suspected cases to the local disease control and prevention center as well as the educational administration agency within two hours.

According to the Ministry of Health, a total of 27 confirmed cases were reported on the mainland yesterday, this pushed the total number of confirmed cases up to 441. Of that figure, 227 patients have already recovered and have been discharged from hospital.

China's first batch of vaccines for swine flu have been produced by a pharmaceutical firm - Hualan Biological Engineering Inc, Xinhua reported on June 22. The vaccine is expected to undergo clinical trials from July.