President Trump said Tuesday a vaccine for COVID-19 could be approved "in a matter of weeks."

"I'm not doing it for political reasons. I want the vaccine fast," Trump said in an interview with Fox News. However, Trump gave only a vague estimate of when the potential vaccine actually could be ready, saying only: "We're going to have a vaccine in a matter of weeks. It could be four weeks; it could be eight weeks.” 

The federal government told states to prepare for a coronavirus vaccine to be ready to distribute by Nov. 1.

The timeline raised concern among public health experts about an “October surprise.” Health officials are concerned a vaccine approval is being driven by political considerations ahead of the presidential election, rather than science, the Associated Press reported.

China also announced it plans to have a vaccine ready as early as November or December, increasing pressure on Trump to push out a vaccine prematurely, the South China Morning Post reported. 

Premature approval would not be the first time the Trump administration had urged health officials to rush questionable treatments. 

In spring, Trump promoted the use of the anti-malarial drug hydroxychloroquine to treat coronavirus. An emergency use authorization was rescinded after researchers determined dangerous side effects were not worth the risk. In late August, Trump pushed an emergency use authorization for a treatment using blood plasma. 

The plasma treatment came into question after Trump and the Food Drug Administration “grossly misrepresented data,” citing a stat that the treatment had reduced deaths by 35%, The New York Times reported. Scientists were taken aback by the way the administration framed the data, which appeared to have been calculated based on a small subgroup of hospitalized COVID-19 patients in a Mayo Clinic study. Patients in the study were less than 80 years old, not on ventilators, and received plasma known to contain high levels of virus-fighting antibodies within three days of diagnosis. 

“For the first time ever, I feel like official people in communications and people at the FDA grossly misrepresented data about a therapy,” Dr. Walid Gellad, who leads the Center for Pharmaceutical Policy and Prescribing at the University of Pittsburgh, told The Times.

Research on the blood plasma treatment still was underway, but the president's emergency authorization halted most clinical trials. 

The unexpected demand for plasma has undercut the research that could prove it works. The only way to get convincing evidence is with a clinical trial that compares outcomes for patients who are randomly assigned to get the treatment with those who are given a placebo. Many patients and their doctors — knowing they could get the treatment under the government program — have been unwilling to join clinical trials that might provide them with a placebo instead of the plasma, The New York Times reported.

In a statement to The Times Dr. Luciana Borio, who oversaw public health preparedness for the National Security Council under Trump and who was acting chief scientist at the FDA under President Barack Obama, said she fears the FDA is “yielding to political pressure.”