Although the current vaccination reduced rates of hospitalization, severity, and death significantly; these vaccines are much less effective in preventing respiratory transmission, which has posed significant challenges for the pandemic control, according to researchers at the Department of Microbiology and State Key Laboratory of Emerging Infectious Diseases, LKS Faculty of Medicine of The University of Hong Kong.

With the emergence of variants, including Omicron and its rapid spread, they said it is urgent to discover a more effective vaccine strategy to block or reduce nasal transmissions.

According to the latest study published in the journal of EbioMedicine by The Lancet, HKU researchers found the combined approach of jab and spray can boost the creation of antibodies on mucosa – the thin skin that covers the inside surface --- as well as lung CD8 T cells. That can prevent animals from getting infected by Covid-19 via nasal transmission.

Currently, HKU is working on the clinical development of two Covid-19 vaccines.

"We are currently testing the influenza-based nasal spray vaccine and the DNA vaccine in humans," said Yuen Kwok-yung, Chair of Infectious Diseases from the Department of Microbiology, who is leading the clinical trials in Hong Kong.

"The biggest challenge for our Covid-19 vaccine development is that we do not have a vaccine manufacturing plant in Hong Kong, which has delayed the translation of scientific discovery into clinical use. Now, we face the same challenge after we have already made the Omicron-targeted DNA vaccine for timely clinical development,' said Professor Chen Zhiwei from the Department of Microbiology, who co-led the research.

Another Professor who co-led the research, Chen Honglin, said using nasal spray vaccination to build up protection in the upper respiratory tract is the key strategy to reduce transmission of Covid-19 and is essential for the ultimate control of the pandemic.