San Francisco, March 21  Twitter has said it will not remove a controversial tweet by Tesla and SpaceX CEO Elon Musk that children are "essentially immune" to the new coronavirus.

The micro-blogging platform flouted its own new rules which say misinformation about children and the coronavirus is kind of content that need to be removed.

A Twitter spokesperson told CNN Business on Friday that it reviewed Musk's tweet and determined it did not break its rules.

Musk had tweeted: "Kids are essentially immune, but elderly with existing conditions are vulnerable. Family gatherings with close contact between kids & grandparents probably most risky".

In its defense, Twitter gave this example: "COVID-19 does not infect children because we haven't seen any cases of children being sick".

Musk's assertion was contradicted at a White House podium by global health expert Dr Deborah Birx, the White House coronavirus task force response coordinator.

"To the moms and dads out there that have children with immune-deficiencies or other medical conditions, we don't know the level of risk," Birx said.

"There is just not enough numbers at this time to tell them if they are at additional risk or not in the same way that adults are. No one is immune. We know it is highly contagious for everyone".

Musk has also downplayed concerns about the coronavirus pandemic, keeping Tesla's California factory open despite a "shelter-in-place" order.

"Maybe we should listen to scientists and not sociopathic grifters," a Musk follower tweeted.

"A kid in my state was just tested positive for it. Even if you are asymptomatic, you can still carry the virus and pass it on to others," tweeted another.