Altimmune Inc. said its influenza vaccine candidate NasoVAX showed additional positive results in a midstage study.

The intranasal vaccine showed a durable, dose dependent protective immune response at six months under the phase 2a study, the Gaithersburg, Md.-based company said in a news release. Serum antibody levels for NasoVAX remained stable through six months compared to an over 50% decline in immune response in patients given Sanofi Pasteur's Fluzone.

Altimmune added that NasoVAX had a better influenza specific mucosal antibody response compared to both Fluzone and placebo. Mucosal antibodies, which can be found in tears and saliva, prevent influenza infection at its site of entry in the respiratory tract.

NasoVAX also showed a clean safety profile under the 60-patient study. The phase 2a trial studied NasoVAX against an H1 strain of influenza.

In March, Altimmune said NasoVAX was well-tolerated at all of its doses and resulted in 100% seroprotection — a metric of protection against infection — at its two highest doses. The earlier analysis of the data showed that NasoVAX also elicited flu neutralizing antibodies similar to Fluzone and a significant T cell immune response compared to Fluzone.