COLUMBIA, Mo. (AP) — Gov. Mike Parson on Thursday said he won't require so-called vaccine passports in Missouri but is comfortable with private companies adopting them.

Vaccine passports, also known as health certificates or travel passes, are documents that show a traveler has been vaccinated against COVID-19 or recently tested negative for the coronavirus.

“If the private sector wants to do that, I'm fine with that,” Parson told reporters. “As far as the state goes, we won't mandate vaccine passports.”

Technology companies and travel-related trade groups are developing and testing various versions of vaccine passports to encourage travel.

Some Republican state senators in Missouri on Wednesday railed against the concept as unduly restricting freedom of travel, proposing that the state pre-emptively ban vaccine passports.

The backlash came as Parson's administration worked to persuade more people to get the COVID-19 shot.

State health Director Dr. Randall Williams on Thursday said eventually “there will be more vaccine than demand because of vaccine hesitancy."

He said he's working on a $5 million project partnering with trusted community leaders to provide information about the vaccine to combat public concerns.

Skepticism about the vaccine is contributing to distribution issues, Williams said, particularly in more rural areas of the state.

He said Missouri sends doses to areas with the most vulnerable people, such as seniors. When there's not enough demand, Williams said the doses are redistributed elsewhere.

“If you're 65 years old, we're going to try to get you the vaccine," Williams said. "And you may choose not to take it, but we're going to have it for you. That creates issues, because when they don't take it then we have to redistribute it.”

Parson also said to expect additional mass vaccination events in Kansas City and other urban areas where there's demand.

The state health department on Thursday reported another 2,145 confirmed COVID-19 cases between March 23 and March 29, which is about 306 new cases a day on average. That's roughly the same number of cases as the week before.