Source: Taipei Times By Lee I-chia / Staff reporter

Local researchers have developed a COVID-19 nasal spray vaccine that has proven to be effective in protecting against the Delta variant of SARS-CoV-2 in animal studies, National Taiwan University Hospital (NTUH) said yesterday.

Worldwide cases of COVID-19 infections have reached more than 250 million and more than 7 billion vaccine doses have been administered, but the pandemic does not seem to be coming to an end, said National Taiwan University Children’s Hospital superintendent Huang Li-min (黃立民), head of the research project.

Current vaccines administered through intramuscular injections were developed in response to the original strain of SARS-CoV-2, but new and emerging variants of the virus have become dominant, so scientists worldwide are trying to develop second-generation vaccines, including nasal sprays and oral doses, he said.

“It is best that the immune system starts to fight back as soon as the virus enters the body, not when it reaches the trachea or lungs,” he said.

Intranasal vaccination could be more effective than injections, as it can induce virus-specific immunoglobulin A (IgA) in the upper respiratory tract, the initial site of infection, he said.

Intramuscular injection vaccines only provide protection to the lower respiratory tract by inducing immunoglobulin G (IgG), but intranasal vaccines can induce both antibodies, in the upper and lower respiratory tracts, which can effectively reduce serious complications and viral transmission, and theoretically reduce breakthrough infections, he said.

The NTUH research team used a special mucosal vaccine adjuvant, for which it has gained a patent, to develop a new COVID-19 nasal spray vaccine, and its experiments on mice showed that it effectively increased the neutralizing antibody titers in the blood in response to the Delta variant, as well as induced IgA, he said.

Intranasal vaccines are also less likely to cause systemic adverse reactions, he said, adding that a nasal spray flu vaccine has been approved for use in healthy people between the ages of two and 49 in the US, so if new COVID-19 nasal spray vaccines are developed and approved, it might increase people’s willingness to get vaccinated.

Moreover, the team designed a trimeric receptor-binding domain of the Delta variant of SARS-CoV-2, which can be used to develop the prototype of a neutralizing antibody assay kit, enabling people to find out how much protection they have against the virus after getting vaccinated, he said.

However, as the prototype of a Delta variant-neutralizing antibody detection kit is expected to be developed within the next couple of months, both the nasal spray and the kit would need further funding to go into clinical trials, he said.