Media release

From: Springer Nature

Development of an inhaled vaccine for COVID-19 

The development of an inhaled vaccine for SARS-CoV-2 is reported in Nature. The compound elicits an increased immune response compared to pre-vaccination and confers strong protection against infection in mice, hamsters, and nonhuman primates, showing promise as an alternative to injections.

Since it was declared a pandemic in early 2020, numerous efforts have been made to develop and approve vaccines for COVID-19. The majority of successful candidates are delivered via intramuscular injections, which induce the production of the antibody immunoglobulin G (IgG). These have proved effective at preventing severe disease, however, they have limited efficacy for preventing infection, as this requires inducing immunity within the mucosal tissue in the lungs and airways. In addition, they are often in liquid form, which necessitates cold chain storage conditions to keep them stable, resulting in increased costs.

Guanghui Ma and colleagues developed an inhalable, dry powder aerosol vaccine for SARS-CoV-2. The vaccine encapsulates a non-toxic bacterial protein called CTB, which is modified to display the SARS-CoV-2 receptor-binding domain antigen, within microcapsules small enough to enter and deposit deep within the lungs. Additionally, a ‘mosaic iteration’ of the vaccine was produced, which contained both ancestral and Omicron variant viruses, to test efficacy against fighting multiple strains.

Following a single dose, the candidate was delivered efficiently to mucosal tissue within the lungs and showed sustained antigen release and successful uptake by antigen-presenting cells. It also induced a long-term increase in IgG and immunoglobulin A (IgA) production in mice, hamsters, and nonhuman primates, which provides effective protection against SARS-CoV-2 infection. The ‘mosaic iteration’ of the vaccine was associated with extending the breadth of this antibody response in both serum and mucus samples, suggesting an effectiveness at tackling co-circulating strains and the Omicron variant. Additionally, the powder was shown to be stable at room temperature after one month of storage, which could reduce the storage and transportation costs of distributing the vaccine, therefore making it more accessible.

This inhaled vaccine shows promise as a way to prevent COVID-19 by targeting the lung cells directly, inducing a more robust immune response than previous inhaled vaccines. The aerosol delivery system has potential as a tool to combat both COVID-19 and other respiratory diseases, the authors conclude.