With COVID-19 infections in India caused by the new XBB.1.16 reorganized strain of Omicron increasing, a Chinese infectious disease specialist has called for vulnerable people to be inoculated with bivalent boosters.

Zhang Wenhong, head of the Center for Infectious Diseases at the Shanghai-based Huashan Hospital of Fudan University, said during a forum on Thursday that vulnerable groups should take booster shots six months after their initial vaccination, either with bivalent vaccines or monovalent vaccines.

Speaking at the Infection and Immunity Summit 2023, jointly hosted by the Shanghai Immunology Society and Frontiers China, he said that China has all types of vaccines. 

"China's bivalent vaccines are gradually becoming available and offer slightly better protection against the Omicron variant, but this data is still only from clinical trials."

The bivalent vaccine – CanSino's bivalent COVID-19 vaccine using messenger RNA (mRNA) technology – was recently approved for clinical trials. 

In January, the company reported "positive" interim data from its experimental COVID-19 mRNA booster vaccine, CS-2034, in a mid-stage clinical trial.

The 433-person trial involved testing a booster shot of the vaccine in people who had already received three doses of an inactivated vaccine, the drugmaker said in a filing to the Hong Kong stock exchange. In 28 days following the booster shots, adults in the CS-2034 group had virus-neutralizing antibodies at levels that were 27 times as high as those in the inactivated vaccine group against the original coronavirus strain, and 23 times higher against the BA.1 Omicron variant, the company said.

XBB.1.16

New COVID-19 variant XBB.1.16, or Arcturus, has been on the World Health Organization's (WHO) radar since March and has been upgraded to "variants of interest" in the organization's latest COVID-19 weekly update, which was released on Thursday.

"Due to its estimated growth advantage and immune escape characteristics, XBB.1.16 may spread globally and contribute to an increase in case incidence. However, at present, there is no early signal of an increase in severity," the WHO said in the release. 

The variant carries an additional mutation in the spike protein, making it more transmissible and is equally as immune evasive as its ancestor strain, XBB.1, the organization said. While it does not appear to trigger more serious symptoms, it could cause severe cases in children, the elderly and those with weakened immune systems.

The strain, which was first reported on January 9, 2023, had been detected in more than 33 other countries as of April 17. According to the WHO, 3,648 cases were reported from countries including the United States, Australia, the United Kingdom, Singapore and Japan, with a major jump in the number of infections in India over recent weeks. 

China's National Administration of Disease Control and Prevention said on Friday that XBB.1.16 is spreading at a very low rate. The proportion of XBB.1.16 cases in imported infections is growing, but the variant has not dominated domestic circulation, it said.