An alliance of patients’ groups on Monday called on the government to provide immunocompromised patients with special long-acting antibody combination jabs, saying conventional vaccines may not be effective enough in protecting them against Covid-19.

The Hong Kong Alliance of Patient's Organizations Limited said studies conducted in the US have found that many patients with a weak immune system – such as those suffering from blood cancer or people who've had organ transplants – were unable to generate enough antibodies after receiving the traditional coronavirus jabs.

The alliance also said the studies showed that while two regular Covid doses were able to reduce the hospitalisation rate for healthy individuals by 91 percent, that fell to just 51 percent for high-risk patients.

Ivan Hung, a government vaccine adviser, said unlike conventional Covid jabs which stimulate a person’s immune system to produce antibodies, the new regimen works by having the antibodies injected directly into the patients’ bodies.

He cited findings published in The New England Journal of Medicine, which suggested that the monoclonal antibody injections could reduce infection risks by 83 percent six months after they were administered.

Hung noted that these shots are currently only available at public hospitals for specific high-risk patients, due to a shortage in supply.

"What we hope to do, of course, is to extend the coverage to others who are also high-risk patients of chemotherapy or biologics or patients on dialysis who would benefit from these monoclonal antibodies,” the expert said.