Starpharma says nasal spray can stop Delta

Starpharma claims the antiviral agent in its Viraleze spray is 99 per cent effective against Delta. (AAP)

A nasal spray being used to prevent COVID-19 is more than 99 per cent effective against the Delta variant sweeping the world, its maker claims.

Melbourne-based biopharmaceutical group Starpharma on Tuesday published test results to show its Viraleze spray, already used in Europe and India, works well against the highly infectious Delta.

Testing in the US found the antiviral agent contained in the spray reduced the spread of the virus by more than 99.99 per cent.

These results came after the virus was exposed to the agent for 30 seconds.

Starpharma claims the spray is also effective against other coronavirus variants.

A single spray lasts for about four to six hours and has been promoted as a handy tool for people travelling with others.

The spray alone does not prevent infection and is designed to be used with other measures such as masks.

While already being used overseas, Starpharma is yet to apply to have the spray approved by Australia's regulator, the Therapeutic Goods Administration.

The TGA this month fined Starpharma $93,240 for advertising the spray on its websites and YouTube to Australians.

Companies are banned from advertising non-approved products.

Investors were encouraged by the Delta tests and sent shares higher by 7.94 per cent to $1.36 at 1402 AEST.

The shares have a record price of $1.95.