A top Louisiana health official has been appointed principal deputy director of the Centers for Disease Control and Prevention (CDC).

With no permanent director of the CDC, Dr. Ralph Abraham, Louisiana's surgeon general, will be the highest ranked official at the agency with a medical degree.

Health and Human Services Secretary Robert F. Kennedy Jr. ousted the former director, Susan Monarez, earlier this year after she refused to preemptively greenlight vaccine recommendations from the agency's advisory panel. Jim O'Neill, Kennedy's deputy, currently serves as the acting CDC director.

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Abraham, a Republican, served as a member of the House of Representatives from 2015 to 2021 before becoming the Louisiana surgeon general in 2024.

As a physician and veterinarian, Abraham has been accused by some health experts of spreading misinformation about COVID-19 vaccine and unproven treatments. In addition, he prevented his state's health department from promoting vaccination efforts.

Abraham did not immediately respond to ABC News' request for comment.

COVID-19 vaccine, treatment misinformation

During and after the pandemic, Abraham has been a proponent of the so-called "medical freedom" movement, which promotes making individual health care decisions without government involvement. In a post on Facebook, Louisiana Gov. Jeff Landry said there was "no better advocate for health freedom" than Abraham.

Some health experts warn that decreased vaccine rates have been correlated to increased outbreaks in the last several years of vaccine-preventable diseases including measles and pertussis.

Abraham previously spread misinformation about COVID vaccines, some health experts have said. In a post on X, in September, he claimed that "the COVID vaccines are dangerous" and made other debunked claims including that contaminants were found in the COVID vaccines.

A December 2022 analysis from the Commonwealth Fund found that COVID vaccines helped prevent millions of hospitalizations and deaths.

Additionally, Abraham backed unproven treatments for COVID such as the anti-malarial drug hydroxychloroquine and the anti-parasite medication ivermectin. Earlier this year, he issued an order allowing any licensed pharmacist to dispense ivermectin to patients aged 18 and older.

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Dr. Nirav Shah, Abraham's predecessor at the CDC, told ABC News that he is concerned Abraham will be promoting misinformation and disinformation to the American public.

"Dr. Abraham's prior job performance and his prior judgment calls are disqualifying as it relates to being the principal deputy director of the U.S. CDC on a number of critical and pivotal issues in public health," he said.

"He doesn't have a good grasp of understanding scientific data, as evidenced by the fact that he embraced the use of ivermectin as a treatment for COVID," Shah continued. "He has labeled the COVID-19 vaccines as dangerous. All of that tells me he's unable to grasp and process scientific and medical data."

Halting promoting mass vaccination

In February, Abraham announced that Louisiana's health department "will no longer promote mass vaccination."

In a memo to staff members, he described vaccines as "one tool in a toolbox" to combat severe illness and that conversations about specific vaccines are best held between an individual and their health care provider.

In a separate, publicly posted press release, Abraham said there is a need to rebuild trust from COVID "missteps" and claimed people have less trust in institutions such as the CDC due to COVID vaccination requirements.

He criticized the then-CDC recommendations that children as young as 6 months receive a COVID vaccine calling it "woefully out of touch with reality and with most parents." Public health experts have repeatedly stressed that COVID vaccines are safe and effective, and especially important in groups at high-risk for worse infections including young children.

Months later, the CDC updated its immunization schedule, dropping the universal COVID vaccine recommendation recommending patients speak to their doctor about the potential benefits and risks before deciding whether or not to receive the COVID immunization.

Over the summer, when Kennedy fired all 17 members of the CDC's vaccine advisory committee, Abraham praised the decision and repeated vaccine misinformation.

"Concerns about vaccines are not mere suspicion but stem from critical analysis of real issues such as historical instances of adverse events, the growing childhood vaccine schedule, the lack of long-term studies comparing health outcomes in vaccinated versus unvaccinated populations and the accelerated approval of certain vaccines with limited safety data," he wrote in an op-ed at the time.

ABC News' Youri Benadjaoud contributed to this report.