(Reuters) -Pfizer on Tuesday reported its first quarterly loss since 2019, as demand fell for its COVID products and it recorded a hefty charge mainly from the U.S. government returning millions of doses of its antiviral treatment Paxlovid. The company recorded a $5.6 billion charge in the third quarter related to Paxlovid and vaccine Comirnaty, most of which was disclosed earlier this month. Pfizer also said the experimental messenger-RNA influenza vaccine it was developing met both its primary goals in a late-stage study in 18- to 64-year olds. It said the vaccine hit secondary immunogenicity goals for influenza A strains, but not B strains of the virus.

Sales of the COVID-19 pill and the vaccine it makes with German partner BioNTech SE had boosted Pfizer's revenue to record levels in the last two years. However, annual vaccination rates have dropped sharply and demand for treatments has dipped as population-wide immunity has increased.

Paxlovid sales slumped 97% in the quarter to $202 million, while vaccine revenue came in at $1.31 billion, down from $4.4 billion last year.

"Despite a messy quarter with many moving parts, we continue to believe that Pfizer's products and pipeline remain under-appreciated," said Cantor Fitzgerald analyst Louise Chen.

Pfizer, which has announced a $3.5 billion cost-cutting program earlier this month, slashed $9 billion off its 2023 sales forecast after agreeing to take back nearly 8 million Paxlovid courses from the U.S. government.

The company posted a loss of 42 cents per share for the third quarter. It had reported a profit of $1.51 per share in the year-ago quarter.

Overall revenue for the quarter came in at $13.23 billion, compared to $22.64 billion a year earlier.

(Reporting by Bhanvi Satija and Khushi Mandowara in Bengaluru and Michael Erman in New York; Editing by Sriraj Kalluvila)