Sen. Ron Johnson, R-Wis., is asking two federal health agencies to review new data from the government of the Czech Republic on mortality rates from COVID-19 vaccines. 

Johnson—who has conducted oversight into the government’s handling of the pandemic—wrote Wednesday to Food and Drug Administration Commissioner Dr. Robert M. Califf as well as Dr. Mandy K. Cohen, director of the Centers for Disease Control and Prevention.

“The Czech data evidences the Moderna COVID-19 vaccine (Spikevax) increased all-cause-mortality (ACM), as measured over a 12-month period from the time of vaccination for every age, compared to the Pfizer-BioNTech vaccine (Comirnaty),” Johnson writes in the letter to Califf and Cohen, a copy of which was obtained by The Daily Signal.

Johnson is the ranking member and former chairman of the Senate Homeland Security and Governmental Affairs subcommittee on investigations. He previously conducted Senate oversight of the government’s response to the COVID-19 pandemic.

In the letter, Johnson cites Steve Kirsch, a Silicon Valley philanthropist who founded the COVID-19 Early Treatment Fund. Kirsch translated and reviewed official Czech Republic government data on COVID-19 vaccines administered there. Kirsch obtained the information through a public records request. 

Johnson’s letter also references analysis by diagnostic pathologist Dr. Clare Craig regarding the Czech data. Craig concurred with Kirsch’s findings.

“I urge you to review the official Czech government data on COVID-19 vaccines administered in the Czech Republic, and Mr. Kirsch’s and Dr. Craig’s analysis on the ACM [all-cause-mortality] of the Moderna and Pfizer COVID-19 vaccines,” Johnson writes. 

He specifically asks the FDA and CDC to review the “one-year and two-year mortality rates from second shot mortality rate for the Pfizer-BioNTech and Moderna vaccine for those injected in 2021, by 5-year age categories.”

Johnson also asks the two agencies to review the “one-year mortality rate ratio for both Moderna and Pfizer, for those who died in high COVID-19 versus low COVID-19 months.” 

“Please explain if your agency is certain that the Moderna and Pfizer vaccines are equally safe,” Johnson writes the two public health officials, “and if so, on what data or studies do you base your opinion?”

Finally, the Wisconsin Republican asks: “Has your agency determined if there is any COVID-19 mortality or any other effectiveness difference between the Moderna and Pfizer vaccines?”

FDA press officer Cherie Duvall-Jones, responding to an inquiry from The Daily Signal, said only: “When the FDA receives a letter from a member of Congress, the agency reviews and responds to the member directly.”

A CDC spokesperson told The Daily Signal, “CDC has received the request from Sen. Johnson and is working to respond.”

The Daily Signal sought comment Thursday morning from the media relations offices of Moderna and Pfizer about Johnson’s letter and the Czech data. Neither responded by publication time Thursday afternoon.