Zhong Nanshan Photo:VCG

Achieving global herd immunity against COVID-19 through mass vaccination will take two to three years, said China's top respiratory disease specialist, Zhong Nanshan.

Zhong made the remarks at a conference of the Science Council of Asia held in Guangzhou, South China's Guangdong Province on Thursday, during which he made a speech about China's COVID-19 prevention and control strategy and vaccine development and shared his views about reaching herd immunity against COVID-19 around the world. 

One way to achieve herd immunity is through natural infection (infection without interference), which means 70-80% of people infected and 5% of people die globally, which would be "unrealistic, unscientific and inhumane," he said. 

Mass vaccination is another way to achieve herd immunity and would require global coordination over a period of two to three years, he said. 

The epidemiologist presented a set of research data on how high vaccination rates should be in different parts of the world in order to achieve herd immunity. 

If vaccine efficacy is 70 percent, then for China, the vaccination rate should reach 83.3 percent of the population, whereas around the world, the rate should be 89.2 percent. 

For Asia and Europe, the rates should reach 80.2 and 96.2, respectively. 

With a vaccine efficacy of 80 percent, 72.9 percent of people in China should be vaccinated to reach herd immunity, while the figure would be 78 percent for the world, 70.2 percent for Asia and 84.2 percent for Europe, according to the statistics that Zhong presented. 

Differences in standard vaccination rates in various areas of the world may be caused by demographic structural factors, such as population density or age distributions in different regions, a Beijing-based immunologist who requested anonymity told the Global Times on Thursday.

At the conference, Zhong said that although China currently leads the world in terms of the number of COVID-19 vaccinations administered, the coverage rate in the country is still lagging, at only about 23 percent. 

But Tao Lina, a Shanghai-based vaccine expert, told the Global Times that China could reach the vaccination rate of 70 percent by the end of 2021 if the vaccine supply is sufficient. 

As of Wednesday, China has administered more than 350 million doses of COVID-19 vaccines. 

Zhong called for herd immunity to be achieved through vaccination as soon as possible to reduce the negative impact of COVID-19 on global economic and social development.

"No country is safe until all countries are safe," he stressed. 

Tao said that countries that achieve herd immunity could gradually open for personnel exchanges between each other. 

Under herd immunity, a new emergence of the epidemic cluster will not cause any exponential increase in infections and can be controlled. 

However, he said uncertainty remains about the pandemic, as factors like virus mutations and the long-term efficacy of vaccines need to be taken into consideration.