"When the new House convenes at noon on Jan. 3, all members will have to be physically present to be sworn in, and they will have to re-pass the rule that allowed the House to vote remotely."

"If, let’s say, five Democrats have covid-19 and are quarantined or hospitalized, or can’t make it to Washington, while all the Republicans can be present, the majority could rest temporarily with the GOP. What would then happen on Jan. 6, when Congress meets in joint session to affirm the electoral college results, is anyone’s guess.... The House has not had a margin this close since after the 1930 election. That year, Republicans won 218 seats but had enough deaths before the convening of the new Congress in March — 14 in all — that Democrats were able to take the majority and hold it when they won a few of the special elections in the interim. The Democrats’ impending mini-majority means there is no leeway for President-elect Joe Biden to choose any more House members for Cabinet positions or other key posts, and there will be heavy pressure put on California Gov. Gavin Newsom (D) not to choose one of the very attractive possible replacements in the House for Vice President-elect Kamala D. Harris’s Senate seat when it becomes vacant on Jan. 20. And, in the meantime, any glitch — an unexpected death or resignation, or even defection, could make a big difference.... [Nancy Pelosi] will have no leeway at all. The speaker will need the support of progressives... and all the Democrats across that wide spectrum. And lawmakers will always think about the next election in 2022, a midterm vote that usually goes against the party holding the White House, making those members from swing or close districts — most of them from the moderate wing of the party — especially antsy and fearful of controversial issues or votes...."

From "Democrats’ House majority is razor-thin. Any glitch could spell disaster" (an opinion piece by Norman Ornstein in WaPo).