(Sharecast News) - Moderna posted a surprise quarterly profit on Thursday, despite sales of its Covid vaccine continuing to slide.

The US biotech said revenues in the three months to December-end were $2.8bn, down on the $5.1bn recorded a year earlier but ahead of forecasts for $2.5bn.

Net income tumbled to $217m from $1.5bn, while diluted earnings per share came in at $0.55.

However, while down notably on last year's $3.61, EPS were well above Wall Street forecasts. Most analysts had been expecting a net loss of around $0.97 per share.

As at 1245 GMT, the Nasdaq-listed shares were up 4% in pre-market trading.

The 43% slide in sales of Moderna's Covid vaccine, its only commercial product, was partially offset by a higher average selling price.

Moderna also recorded $600m in deferred revenue from its work with vaccine NGO Gavi during the quarter.

The Covid vaccine, which was granted emergency approval in the US in 2020, was the biotech's first marketable drug.

It generated billions for the firm but demand, in line with all Covid vaccines, has fallen significantly since the peak of the pandemic.

In response, Moderna is looking to adapt the technology for other diseases, most notably for RSV, influenza and cancer.

Stephane Bancel, chief executive, said: "2023 was a year of transition for Moderna as we adapted to the endemic market. At the same time, our development team made significant pipeline advancements across infectious diseases, oncology and rare diseases, while our commercial team increased our Covid-19 market share in the US.

"We look forward to the anticipated approvals of our RSV vaccine beginning in the first half of the year."

Moderna also reiterated its 2024 forecast for sales of $4bn.

Analysts expect the RSV vaccine to generate around $280m in 2024, according to Reuters.