The successful containment of the COVID-19 Delta variant in densely populated Guangdong province during its local outbreak earlier this year proves vaccination is effective, an official from China's top health body said Thursday.

He Qinghua with the National Health Commission said at a news conference current vaccines are still proving effective in reducing virus transmission and lowering the incidence of severe illness and mortality.

Starting in late May, Guangdong province started to see local cases appear. By the end of June, when the outbreaks were completely contained, 167 cumulative cases were reported. These cases were especially concerning because they involved the Delta strain, which is known to be highly contagious.

The province is highly populated. Its capital city Guangzhou, where the most cases were reported, has a population of more than 15 million people.

He said successful control in Guangdong province, an area with dense population and rapid movement of people, proves getting vaccinated, wearing masks, washing hands regularly, keeping social distance and avoiding crowds are effective measures.

The Delta variant was first detected in India in September and the World Health Organization announced in May the new strain is of global concern. It has spread in more than 130 countries and regions and is characterized by an advanced transmission capability.

He noted research at home and abroad has shown the new variant has not caused a drastic change in the biological features of the novel coronavirus. The source of infection and transmission route are clear, and the current epidemic prevention and control measures are still effective.