On Monday, Moderna said its vaccine is effective against new variants that have emerged in Britain and South Africa. But the immune response is slightly weaker against the variant discovered in South Africa, so the company is developing a new form of the vaccine that could be used as a booster shot against that virus.
And Dr. Rochelle Walensky, the new C.D.C. director, offered a blunt assessment of the vaccination campaign on Sunday, predicting that supply would not increase until late March.
Federal health officials and corporate executives agree that it will be impossible to increase the immediate supply of vaccines before April because of lack of manufacturing capacity. A third vaccine maker, Johnson & Johnson, is expected to report the results of its clinical trial soon. If approved, that vaccine would also help shore up production eventually, though the company has manufacturing issues of its own.
“I can’t tell you how much vaccine we have, and if I can’t tell it to you then I can’t tell it to the governors and I can’t tell it to the state health officials,” Dr. Walensky told “Fox News Sunday.”
Mr. Biden’s travel ban is a presidential proclamation, not an executive order. Typically, proclamations govern the acts of individuals, while executive orders are directives to federal agencies. It will go into effect on Saturday and apply to non-U.S. citizens who have spent time in South Africa in the past 14 days. The new policy, which was reported earlier by Reuters, will not affect U.S. citizens or permanent residents, officials said.
The airline industry had no immediate comment on the new travel bans. But airline officials point to studies by the World Health Organization showing that the impact of travel bans on curbing the spread of infectious disease is limited. President Donald J. Trump came under intense criticism after he banned travel from China, and the ban proved porous as tens of thousands of people still came into the United States from that country.
“I think of travel bans as helpful but hardly foolproof,” said Dr. Ashish Jha, the dean of the Brown University School of Public Health. Mr. Trump’s China travel ban “probably slowed things down, and that’s reasonable,” he said. But travel bans need to be coupled with other policies to be useful, he said.