Virus transmission advice disappears from the CDC website

U.S. Health Officials believe coronavirus vaccine could be widely available by April

Outside experts have expressed concern the administration is pressuring health authorities to approve a vaccine before the presidential election in November.

Fauci said several kinds of vaccines are in final-stage testing in the US.

At least one expert said the episode could further chip away at public confidence in the CDC.

Marr said she was surprised to see that the CDC guidance posted Sunday said that inhalation of droplets and aerosols are the main way the virus spreads.

The Centers for Disease Control and Prevention pulled new guidance it had quietly posted over the weekend warning of the dangers of airborne transmission of the coronavirus, saying the information was "posted in error". The CDC previously said the virus can spread through aerosols as well but later deleted and updated without any announcement.

Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, is pictured in a hearing on July 31.

Trump, however, questioned why a vaccine would need to be delayed and said such a proposal by the FDA would appear to be politically-driven.

But Trump made clear at a Wednesday evening White House news conference that he was sceptical of any regulatory changes that might delay a vaccine's authorisation, even if those changes are aimed at increasing public trust. "We haven't seen the data from the clinical trials, and we won't until they come to us". "These findings were from experimentally induced aerosols that do not reflect normal human cough conditions", World Health Organization says.

"Our position on this remains the same and we've always said going back over months and months about the potential for different kinds of roots of transmission and particularly driven by the context, the proximity, the intensity, the duration and the potential for different forms of transmission", Dr Ryan added. The FDA declined to comment when a CNN reporter asked about the president's remarks.

A top US health official told a US Senate committee on Wednesday that he expects COVID-19 vaccinations to take place over many months and that most Americans could be vaccinated by July of 2021 at the latest.

On Thursday, Hahn vowed that it would be scientists who determine a vaccine's fate.

President Donald Trump stomped on a united front by claiming he may override the FDA if the agency released tougher standards for the authorization of a vaccine.

Redfield and Hahn defended their agencies against criticism of their handling of the pandemic, telling the committee they were using science as their guide, not politics.

A federal official who was familiar with the matter said there was no pressure involved in the change.

On Monday, Trump said the worst was over, as the death toll reached 199,660 with more than 6.8 million confirmed cases, according to the Johns Hopkins University tally.