Chinese COVID-19 vaccines are safe, and the theory that taking the vaccine will cause leukemia or diabetes is completely false, scientists said on Saturday.

Feng Zijian, vice-president of the Chinese Preventive Medicine Association, said that 3.4 billion homegrown COVID-19 vaccines have been administered and the monitoring data shows that domestic vaccines are very safe, with the rate of adverse effects being slightly lower than that of regular vaccines, such as those against polio and influenza.

As of May 30, the mainland had administered 3.38 billion COVID-19 doses, and received about 238,000 reports of adverse reaction following immunization.

Feng added that foreign countries using Chinese vaccines for public vaccination also found no safety issues.

Wang Fusheng, an academician with the Chinese Academy of Sciences, also refuted online rumors that COVID-19 vaccination was associated with increased incidence of leukemia, diabetes and cancer metastasis.

"If COVID-19 vaccines could trigger these diseases, we should have seen a marked increase in hospital visits and hospitalizations. But in reality, there is no such rise," he said.

According to health experts, domestic vaccines can provide protection against the highly infectious Omicron BA.4 and BA.5 variants of the novel coronavirus.

Feng said scientists are also advancing research into vaccines specifically targeted at the Omicron strains of the virus, as well as broad-spectrum vaccines and those based on the mRNA technology.