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A team of US scientists has discovered a potential intranasal vaccine candidate that exhibits improved and longer-lasting immunity against SARS-CoV-2 compared to traditional injection-based vaccines. The intranasal approach triggers an immune response directly at the entry point, potentially providing enhanced, durable immune memory against the virus, reducing the need for frequent booster shots.
Published in the journal eBioMedicine, the study indicates that the intranasal vaccine candidate not only boosted mucosal antibody response, as expected, but also demonstrated more prolonged mucosal and systemic immune protection. This was achieved through the preferential induction of airway-resident T cells and central memory T cells.
Lead author Ashley St John, Associate Professor at Duke-NUS’ Emerging Infectious Diseases Programme, highlighted that the intranasal route improved the response of T cells, reducing disease severity. Additionally, it resulted in a higher number of T central memory cells compared to subcutaneous vaccination, potentially leading to longer-lasting protection.
T central memory cells are crucial for retaining long-term memory of a virus, providing lasting protective immune responses. This finding suggests that intranasal vaccination might require fewer boosters to achieve and maintain a similar level of protection against the virus.
The study also explored the influence of adjuvants, substances added to vaccines to enhance the immune response. Adjuvants were found to influence the characteristics of T-cells, their activation, and cytokine production. Different adjuvants led to distinct T-cell responses.
Professor Patrick Tan, Senior Vice-Dean for Research at Duke-NUS, emphasized that while the acute phase of the pandemic may be receding, the emergence of new variants underscores the need for more effective tools in the fight against COVID-19. The study suggests that mucosal vaccination, especially intranasal approaches, holds promise for improving vaccine efficacy and potentially reducing the frequency of booster shots.
