HKU researchers see promise in nasal spray Covid vaccines

Nasal spray Covid vaccines can act as boosters to improve the effectiveness of jabs, according to University of Hong Kong researchers.

The university's faculty of medicine is currently developing two types of nasal sprays by its school of biomedical sciences and department of medicine.

But they have yet to undergo large-scale clinical trials and it is unknown when they can be launched.

Speaking on television, Jin Dongyan said the spray his biomedical sciences team is developing contains weakened coronavirus, which stimulates the body to generate antibodies as if the recipient has suffered a natural infection. It will enter clinical trials this year.

"Now we know that it can prevent animals from contracting the infection," he said.

But Jin added even if the coronavirus is weakened, it is a living one.

"Living coronavirus may lead to certain side effects. It may be dangerous for immunocompromised people," he said.

Ivan Hung Fan-ngai, taking part in the development of the spray by the department of medicine, said it has passed a phase one clinical trial and will soon proceed to phase two.

He believed people who have received vaccines both by injection and nasal spray will have stronger immunity against Covid.

"If people have taken the vaccines by injection and a booster by nasal spray, it is possible that they have a better immune response in the cells and more antibodies in the blood," he said. "It's especially good because they'll also have antibodies in the nasal cavity, which is better than just having injections."

Because of mutations in the virus, both teams had to refine their products, he said.

Asked how many more vaccine doses people need to take, both experts said the answer depends on mutations.

"It's likely the virus will become a seasonal infection, like seasonal influenza. In that case, we may have to take a booster dose every winter for the next several years," Hung said.

Jin said: "That will depend on how weak the virus will become. If it's as weak as the four other common coronaviruses for humans, it may even be unnecessary to get jabbed."

Both teams admitted their products are still far away from completing all clinical trials and being launched in the market. They believe Hong Kong has to partner with mainland pharmaceutical firms to manufacture the vaccines.

So far 80.1 percent of the SAR's eligible population have been vaccinated, with 5.39 million receiving at least one dose. Among them, 4.86 million have taken two doses. More than 1 million have also got booster jabs.

Chief Executive Carrie Lam Cheng Yuet-ngor on Friday said the no jab, no entry vaccine pass - to be launched in restaurants and regulated premises on February 24 - would eventually require three doses.

jane.cheung@singtaonewscorp.com