Where did COVID-19 come from? We’ll probably never know.

As world deaths rise to close to 5 million, U.S. intelligence agencies say they won’t be able to conclude whether COVID-19 spread by animal-to-human transmission or leaked from a lab,

Officials have released a fuller version of their review into the origins of the pandemic. China has resisted global pressure to cooperate fully with investigations into the pandemic or provide access to genetic sequences of coronaviruses kept at the Wuhan Institute of Virology, which remains a subject of speculation for its research and reported safety problems.

President Joe Biden launched the review amid growing momentum for the theory — initially broadly dismissed by experts — that the virus leaked from the Wuhan lab. Former President Donald Trump and his supporters long argued that a lab leak was possible as they sought to deflect criticism of his handling of the pandemic.

Four agencies within the intelligence community said with low confidence that the virus was initially transmitted from an animal to a human. A fifth intelligence agency believed with moderate confidence that the first human infection was linked to a lab.

Here’s a roundup of other COVID-19 developments this weekend:

Also this week, U.S. regulators authorized Pfizer’s vaccine for younger children after millions of 12- to 17-year-olds already safely got the shot, the only one available for children in the country. Here’s an update for parents: