Polytechnic University researchers on Thursday said they have developed a portable Covid antibody test kit that lets people know when they should receive their next booster shot using saliva instead of blood.

They explained people will need to place saliva on a tiny chip attached to a palm-sized reader and then add a few drops of electrolyte.

After six minutes, the reader will transmit data to the user’s smartphone, which will display a numeric reading and colour indication representing their antibody level.

Helen Law, an associate radiography professor with the university and part of the research team, said they put protein on the chip that can effectively detect Covid antibodies.

"It is an ultrasensitive device, and that's why we have the advantage of detecting the antibodies inside the saliva," she said.

Law explained antibody levels may slowly drop after a dose of Covid vaccine, adding the new technology should help people determine when a booster is needed.

“This device can be used to monitor the antibody level, and then at the same time give us some information [like] maybe this individual has a very low response to the vaccination, and maybe we should advise this [person] to have an extra booster."

Applied physics professor Yan Feng, who led the study, said their technology is quicker and cheaper than laboratory tests that check antibody levels.

He said the chip only costs HK$10 to make, while laboratory tests, which take up to two days to produce results, cost between HK$500 and HK$2,000.

Yan added while their test kit is not the first portable Covid antibody detection device, other options cannot show a person's antibody level.