Taipei, Nov. 23 (CNA) A National Taiwan University Hospital (NTUH) research team announced on Tuesday that a COVID-19 nasal spray vaccine currently under development that targets the Delta variant has shown promising initial results following tests on mice.

Although over 7 billion doses of COVID-19 vaccines have been administered worldwide, there are few signs the pandemic is abating, Huang Li-min (黃立民), superintendent of National Taiwan University Children's Hospital, who heads the research team, said at a news conference held to publish the early findings of the research.

Currently, most approved COVID-19 vaccines are administered via intramuscular injections aimed at the Wuhan strain SARS-CoV-2, the virus that causes COVID-19.

However, these are less effective in preventing infection from the Delta variant, which was first detected in India a year ago, prompting researchers around the world to explore more effective COVID-19 vaccines, Huang said.

Like foreign scientists, NTUH researchers have begun to develop a second generation COVID-19 vaccine in the form of nasal sprays or tablets taken orally, according to Huang.

Their work uses the homotrimer spike glycoprotein of the Delta variant's receptor-binding domains (RBD) as an antigen to develop vaccines and neutralizing antibody reagents that target the variant.

Tests show that the nasal spray vaccine developed by the NTUH team using a patent mucosa immunologic adjuvant is better at increasing spike protein specific antibodies and neutralizing antibodies in lab mice, outperforming current vaccines administered via the intramuscular route, Huang said.

COVID-19 vaccines given via intramuscular injection only produce antibodies in the lungs to reduce serious cases of pneumonia, but cannot stop infection.

In contrast, the COVID-19 nasal spray vaccine being developed by NTUH can create antibodies in the nasal cavity and effectively lower the viral load in the upper respiratory tract, which will hopefully help reduce the number of Delta variant breakthrough cases, he said.

Currently, seven types of COVID-19 nasal spray vaccines are being developed worldwide, and the key to their potential success lies in the adjuvant, Huang noted.

The special adjuvant developed by Huang's team can mix with the antigen of any brand of COVID-19 vaccine currently available on the market to produce neutralizing antibodies and effectively deal with any new strains, he added.