By Brendan Pierson

(Reuters) - The U.S. state of Kansas on Monday sued Pfizer, accusing the company of misleading the public about its COVID-19 vaccine by hiding risks while making false claims about its effectiveness.

In a lawsuit filed in the District Court of Thomas County, the state said the New York-based drugmaker's alleged false statements violated the Kansas Consumer Protection Act. It is seeking unspecified money damages.

"Pfizer made multiple misleading statements to deceive the public about its vaccine at a time when Americans needed the truth," Kansas Attorney General Kris Kobach, a Republican, said in a statement.

The lawsuit claims that, beginning shortly after the vaccine's rollout in early 2021, Pfizer concealed evidence that the shot was linked to pregnancy complications, including miscarriage, as well as inflammation in and around the heart, known as myocarditis and pericarditis.

"The representations made by Pfizer about its COVID-19 vaccine have been accurate and science-based," Pfizer said in a statement, adding that it believed the lawsuit had no merit.

The U.S. Food and Drug Administration in June 2021 added a warning about myocarditis and pericarditis to the vaccine's label. The side effects are rare and most often occur in adolescent boys and young men.

A 2023 review of 21 studies by the U.S. National Institutes of Health concluded that COVID vaccines were not linked to miscarriage.

Kansas also said Pfizer falsely claimed that its vaccine, which was developed with German partner BioNTech for the original strain of the virus, retained a high effectiveness against mutated variants, and that it would prevent not only illness but transmission.

Texas Attorney General Ken Paxton filed a similar lawsuit against Pfizer last year, which remains pending. Pfizer has also called that case meritless.

Kobach said on Monday that other states had been collaborating with Kansas in its investigation and are expected to file lawsuits as well.

BioNTech is not a defendant in the case.

(Reporting By Brendan Pierson in New York, Editing by Alexia Garamfalvi and Bill Berkrot)