Needle-free vaccine candidate promises improved, longer-term immunity against COVID-19

Researchers from Duke-NUS Medical School (Duke-NUS) have discovered a new vaccine candidate that can be delivered through the nose (nasal) in the form of a spray that promises better and longer-lasting immunity against COVID-19 compared to the conventional COVID-19 vaccine administered through the skin (subcutaneous) via injections.

Since the U.S. Food and Drug Administration approved the first COVID-19 vaccine in 2021, vaccination became our primary defence against serious symptoms from a COVID-19 infection. There is mounting evidence that a more targeted approach of vaccine delivery – through our airways – can provide greater and prolonged protection against COVID-19 and potentially reduce subsequent infections.

Past research showed that nasal vaccines induce an immune response on the inner surfaces of the upper respiratory tract where the SARS-CoV-2 virus – which causes COVID-19 – will usually initiate its infection.

In a recent preclinical study published in eBioMedicine in December 2023, Duke-NUS researchers compared the immune responses from administering the vaccine through the nose and skin. The researchers also examined how the body’s immunity is affected when the vaccine is coupled with adjuvants, which are compounds used to elicit stronger immune responses in individuals receiving the vaccine.

Enhancing longer-lasting immunity

T central memory cells are immune cells that confer immunity against various foreign bodies, such as viruses, bacteria and cancer cells. These immune cells play an important role in building up the body’s adaptive immunity, allowing the immune system to remember viruses that have infected the body and establish protective mechanisms against these viruses, providing long-term immunity.

To determine whether administering a nasal vaccine can provide longer-term protection against COVID-19 infection, the Duke-NUS team compared the T cell responses when the team delivered the vaccine through the nose and the skin.

Lead author of the study, Associate Professor Ashley St John, who is from Duke-NUS’ Emerging Infectious Diseases Programme, explained, “Compared to injecting the vaccine through the skin, delivering the vaccine through the nose improved the response of certain T cells, particularly T central memory cells, which reduced disease severity.”

“Not only that, it also resulted in a greater number of T central memory cells compared to vaccinating through the skin, which could lead to longer-lasting protection,” added Assoc Prof St John.

Boosting protection against COVID-19 infections

On top of longer-lasting immunity, the research team also discovered that COVID-19 vaccine administered through the nose could induce antibody responses that have a greater capacity to protect the body against different variants of the SARS-CoV-2 virus. This discovery provides key scientific evidence supporting the idea that nasal COVID-19 vaccines can contribute to greater protection and longer-lasting immunity.

“While the acute phase of the pandemic may be behind us, the rise of new variants, including JN.1 which has triggered an increase in hospital admissions locally, demonstrates that we have room in our arsenal of vaccines and treatments for even better tools. This study shows that mucosal vaccination holds promise for improving COVID-19 vaccine efficacy with potentially fewer boosters needed,” said Professor Patrick Tan, Senior Vice Dean for Research at Duke-NUS.

Next steps

The researchers have filed a patent for the vaccine composition created for nasal vaccines. This will pave the way for industrial partnerships to develop better vaccines against COVID-19 and other pathogens that target the upper respiratory tract.