INNA-051: Nasal Spray Aims to Shield Against Multiple Respiratory Viruses

A nasal spray candidate designed to provide broad protection against multiple respiratory viruses is advancing through clinical trials in the United States.

This development occurs against a backdrop of shifting infectious disease patterns in 2025, characterized by co-circulating pathogens, altered seasonality, and a resurgence of certain vaccine-preventable illnesses.

Nasal Spray INNA-051: Clinical Development and Purpose

INNA-051 is being developed by ENA Respiratory, a biotechnology company based in Melbourne. The compound aims to stimulate the innate immune system at the nasal passage—the primary entry point for respiratory viruses—to offer broad protection against pathogens including influenza, respiratory syncytial virus (RSV), and SARS-CoV-2.

Professor Nathan Bartlett, a viral immunologist at the University of Newcastle and HMRI’s Infection Research Program, contributed to the preclinical research conducted over five years. The compound was initially developed to improve vaccine effectiveness but was found to provide antiviral protection without a vaccine.

"The concept involves boosting the body's natural ability to defend itself at the nasal entry point, potentially covering multiple viruses."

Funding and Trial Status

ENA Respiratory has secured over $46 million in funding from organizations including the Gates Foundation and the Minderoo Foundation, plus an $18 million contract with the US Department of Defence.

• A Phase 2 safety study involving 200 participants has been completed.
• A larger Phase 2 trial involving 900 people is planned, focusing on high-risk groups such as university students, households with young children, and childcare settings.

Professor Bartlett noted that vaccination remains an effective preventive measure and recommended staying home when unwell, practicing good hand hygiene, and avoiding close contact with vulnerable individuals.

2025 Respiratory Virus Landscape

According to analysis informed by Professor Bartlett and data from NSW Health, 2025 saw several notable trends in infectious diseases.

COVID-19 Presence

COVID-19 maintained a steady, low-level presence throughout 2025, integrating into the broader mix of respiratory pathogens without causing major pandemic-era waves. NSW Health data indicated generally low virus levels, with moderate peaks observed in January and June.

Several new variants emerged:

• Early 2025: XEC and KW.1.1
• Late 2025: XFG, NB.1.8.1, PE.1.4, and BA.3.2

Influenza and RSV Dynamics

Influenza showed increased prevalence in 2025, particularly during the second half of the year. Professor Bartlett noted disruptions to typical respiratory pathogen patterns, including altered seasonality.

Influenza and RSV co-circulated with SARS-CoV-2, at times outside their usual seasonal windows, leading to unpredictable peaks and multi-wave respiratory seasons.

NSW Health data reflected a traditional winter flu wave peaking in July-August, alongside an additional surge in November and December. This early summer spike was attributed to a new variant of Influenza A (H3N2), subclade K.

RSV circulated at relatively low levels overall but disproportionately affected specific age groups. Nearly half of all lab-confirmed RSV cases in NSW were among children aged 0-4 years. Bronchiolitis-related hospital admissions in this demographic remained stable compared to 2024.

Other Respiratory Infections

Additional respiratory pathogens continued to circulate in 2025:

Non-Viral Outbreak: Salmonella

A notable non-viral outbreak originated from alfalfa sprouts. A national recall of Parilla Fresh alfalfa sprouts was issued in November due to Salmonella contamination. An unusual strain of Salmonella affected over 44 individuals across Australia, including at least 18 in NSW.

Co-infections

2025 reflected a continued trend of co-infection, where individuals are infected with more than one pathogen concurrently.

Mixed infections—encompassing both viral-viral and viral-bacterial combinations—became more common, particularly in children under five.

Studies reported up to 34% of cases involving bacterial-viral co-infections, which complicates clinical management. Common examples included respiratory viruses like RSV or influenza alongside bacterial infections such as pneumonia or ear infections.

Vaccine-Preventable Diseases

Globally, 2025 saw an increase in vaccine-preventable diseases, a trend also observed in Australia.

Whooping Cough (Pertussis):

• A resurgence occurred post-pandemic, with some countries reporting tenfold increases compared to pre-pandemic baselines
• Over 24,000 cases recorded across Australia, with almost 9,400 in NSW
• While the national total decreased from 57,000 in 2024, figures remained double those of 2019

Measles:

• Resurged after years of low transmission in Australia
• Over 160 national cases, including 30 in NSW
• Represents an increase from 57 confirmed cases in 2024

Implications and Public Health Measures

Infectious disease patterns showed reduced predictability in 2025. With COVID-19 integrated into the broader respiratory pathogen mix, illness waves occurred at atypical times, increasing anticipation challenges.

Professor Bartlett emphasized that disease surveillance is critical for rapid response and information dissemination, particularly for populations at high risk of severe disease.

High-risk groups include:

• The very young
• The elderly
• Immunocompromised individuals
• Those with chronic illnesses

FluTracking, a joint initiative, provides a mechanism for public health contribution, where symptom reporting assists researchers and health authorities in early outbreak detection and response.