A preclinical study of Altimmune’s single-dose intranasal Covid-19 vaccine, AdCOVID, has demonstrated positive results, with no detectable levels of infectious virus in the lungs of vaccinated mice after challenge with the SARS-CoV-2 virus.

In a SARS-CoV-2 challenge model, a single dose of the vaccine delivered sterilising immunity in the lungs of mice, while non-vaccinated mice went on to develop dense lung infection and disease.

AdCOVID can potentially induce a wide immune response including systemic and local immunity in the nasal cavity and respiratory tract, the company said.

In the study, carried out in partnership with the University of Alabama at Birmingham, K18-hACE2 transgenic mice were given a single intranasal dose of AdCOVID and challenged with live SARS-CoV-2 after a month.

Data showed no recognisable levels of SARS-CoV-2 in the lungs of vaccinated mice, indicating over a one-million-fold decrease in virus levels versus the non-vaccinated mice.

The sterilising immunity showed by AdCOVID in this study is comparable to the vaccine candidate’s induction of local and systemic immunity in earlier animal studies, Altimmune noted.

Altimmune chief scientific officer Scot Roberts said: “These data suggest that a single intranasal vaccination with AdCOVID may provide sterilising immunity that neutralises infectious virus, which is believed to be the best way to block viral transmission.

“Blocking transmission is critical for preventing spread of the virus and preventing the emergence of new variants of concern, both of which have the potential to prolong the pandemic.”

In previous preclinical studies, the vaccine candidate demonstrated a 29-fold stimulation of spike-specific IgA and resident memory T-cell responses in the lungs of the animals tested.

Currently, AdCOVID is being evaluated in a Phase I clinical trial for safety and immunogenicity of one or two intranasal doses given a month apart. Altimmune anticipates reporting data from this trial next month.

Separately, Novavax reported that a combination of its Covid-19 vaccine candidate NVX-CoV2373 with quadrivalent seasonal flu vaccine NanoFlu led to immune responses against SARS-CoV-2 and influenza in a preclinical study.