In the first study of its kind around the world, researchers from Chinese University have found that people lacking the bacteria named "bifidobacterium adolescentis" showed a poor antibody response to Covid-19 vaccines.

They suggest that supplementing this bacterium to one's body may help to increase antibody levels, which can be an alternative to booster jabs.

CUHK found in an earlier study of over 2,000 citizens that bifidobacterium adolescentis was either very low or absent in 85 percent of otherwise healthy Hong Kong people.

The university then collaborated with the University of Hong Kong to recruit 138 residents aged 18 to 67 who had completed two doses of the Covid-19 vaccine.

Over half of the people lack the bacteria, which resulted in a poorer antibody response to Covid-19 jabs.

All participants provided blood and stool samples before vaccination and one month after the second dose for the research team to measure their antibody level in relation to their gut bacterial composition.

The results showed that people lacking the bacteria showed a poor antibody response.

Bifidobacteria belong to a family of probiotic bacteria in human beings' guts. According to the team, Bifidobacterium adolescentis lives in people's gut from birth, and its abundance declines rapidly with age, modern diet, stress, and the use of antibiotics.

Diet alone cannot restore this precious bacterium once it is lost. Many health products contain bifidobacteria, but very few have bifidobacterium adolescentis.

After the age of 60, the team said the level of Bifidobacterium adolescentis decreases, which may lower the level of antibodies after the Covid-19 vaccination.

Professor Ng Siew-chien, Associate Director of the Centre for Gut Microbiota Research at CU Medicine, said that this was the first proof in humans that Bifidobacterium adolescentis plays an important role in modulating the efficacy of Covid-19 vaccines.

She said that the Sinovac vaccine is known to have fewer side effects but suffers from relatively lower antibody response, but the study offered a potential solution to enhance its efficacy.

Ng also said that the university will continue clinical studies to understand whether supplementation of Bifidobacterium adolescentis can replace regular jabs of the Covid-19 vaccine.

The team also said that the public can assess whether they have sufficient antibodies after vaccination by testing the level of Bifidobacterium adolescentis.

However, the team reminded that in addition to the prohibitive cost, relevant testing also requires university-level research techniques and that people are suggested to take their health seriously and improve their intestinal microbiology rather than undergo unnecessary tests.

Francis Chan Ka-leung, Dean and Director of the Centre for Gut Microbiota Research at CU Medicine, said that this is the first human study of its kind in the world, and they believed that this discovery offers a novel approach to optimize vaccine efficacy and safety through modulation of the gut microbiota.

"It may become the treatment of Covid-19 patients in the future," Chan said.