HOUSTON: A US judge has thrown out a lawsuit by more than 100 employees of one of Texas's largest hospitals, who sued after being required to get vaccinated against Covid-19.

They argued Houston Methodist Hospital's demand was illegal so long as the available shots have received only emergency use authorization from US health authorities -- though that authorization has cleared the way for millions of Americans to be vaccinated.

The hospital set a June 7 deadline for workers to prove they had received at least one dose or face termination.

Federal court Judge Lynn Hughes ruled against Jennifer Bridges and 116 other workers on Saturday, saying the vaccines' safety was not at issue and Texas law only protects employees from refusing to commit a crime.

"Receiving a Covid-19 vaccination is not an illegal act, and it carries no criminal penalties," Hughes wrote.

She also reprimanded Bridges for the analogy that the threat of being fired for not getting vaccinated was like "forced medical experimentation during the Holocaust."

"Equating the injection requirement to medical experimentation in concentration camps is reprehensible," Hughes wrote.

Houston houses the largest medical complex in the world, the Texas Medical Center, a sprawling district that includes hospitals and research universities. The center employs more than 106,000 healthcare workers in all, and sees some 10 million patients a year.

Across the United States, more than 173 million people -- over 50 percent of the population -- have received at least one dose of a Covid-19 vaccine so far.

And yet, surveys show that healthcare workers have been among the greatest vaccine skeptics.