What kind of information do you imagine the leadership of the most powerful military and intelligence organization in human history might have?

If it was intelligence that any investor could have gathered themselves, that's not non-public. It doesn't matter that the government are the best investigators.

we don’t know what was said at the briefing.

Insight into multiple companies' preparedness heading into a pandemic would make it easy to pick winners and losers

What non-public information about companies' preparedness would they have? Couldn't any investor research a company's pandemic preparedness? What special information about that does Congress have access to that we don't?

Considering the pandemic became a pandemic in March and they sold stocks in February, your question reads as loaded.

The pandemic was definitely a "thing" through all of February, just binned as something that happens to Other People. February 24th was when US stock markets started to really react, and it was maybe 2 weeks until major US cities were making decisions like schooling from home.

There was plenty of opportunity through January and February for "prescient" trading decisions. The main decisions in question are those executed by US legislators immediately following a national security briefing. I'm not saying it's illegal, it's not; but they're assholes for selling after the briefing and still deliberately telegraphing otherwise.

I hedged my portfolio in January. You didn’t need a declaration of pandemic by the WHO to see the risk — that’s a trailing indicator. I exited my initial hedges in mid-March.

Which isn’t to defend or justify insider trading by Congress. There were intelligence analysis reports floating around Washington DC in 2019, so it was a known risk. But you didn’t need to be a beltway insider to see that possibility when insuring against that risk was very cheap.

It was becoming fairly obvious by February even to people outside of Congress (such as myself) that a global pandemic was likely impending. I didn't attend any secret briefings.

What nonpublic information about a publicly traded company do you think they received?

Representatives of the US government sold stocks, meanwhile many Americans only received “it’s the flu”, “this will be over in a few months guaranteed”. I didn’t assert anyone received info about a company. I’m only pointing out to the parent comments author that stocks were being dumped by congress prior to there being a pandemic. I don’t know what information was given in a secret report, if I did, it wouldn’t be a secret.

It doesn't matter what messages laypeople received from the media. All that matters is if those laypeople were capable of discovering the same facts which congresspeople had access to. Congresspeople were also subject to those messages in the media which downplayed the severity of the virus, and many laypeople also sold stocks in February despite the media opinion.

You seem smart, and if you published an email address in your profile, other smart people who want to connect and discuss things with you could send you email. :)

PS: email me