Here are the most important news, trends and analysis that investors need to start their trading day:

• Futures mixed a day after Dow closes at a record
• Weekly jobless claims fall to pandemic low ahead of Friday's jobs report
• Moderna says early data shows Covid vaccine 96% effective in adolescents
• U.S. backs waiving patent protections for Covid vaccines
• SEC chair to testify on short-selling, derivatives after GameStop, Archegos gyrations

1. Futures mixed a day after Dow closes at a record

U.S. stock futures were mixed Thursday after strong earnings and economic optimism pushed the Dow Jones Industrial Average up nearly 100 points to a record closing high. The S&P 500 eked out an advance Wednesday, ending about 1% from last month's closing record. The tech-heavy Nasdaq fell modestly, finishing roughly 4% from its April record closing high. Amazon, Netflix and Facebook, which all dropped over 1% on Wednesday, were steady in Thursday's premarket trading.

2. Weekly jobless claims fall to pandemic lows ahead of Friday's jobs report

The Labor Department on Thursday reported that initial jobless claims sank to a pandemic-era low of 498,000 last week, better than expectations and down 92,000 from the prior week. That's the lowest tally of new filings for unemployment benefits since mid-March 2020 when they totaled 256,000 and the first time under 500,000 since then. U.S. companies' April payrolls showed big gains but short of lofty expectations, according to the ADP's latest monthly report issued Wednesday. The ADP data during Covid has consistently undershot the government's official monthly tally, which is due out Friday.

3. Moderna says early data shows Covid vaccine 96% effective in adolescents

Moderna said its Covid vaccine was 96% effective in kids ages 12 to 17, according to early data released Thursday along with the company's mixed first-quarter earnings and revenue. Shares fell more than 9% in the premarket. On Wednesday, citing early data from another ongoing trial, Moderna said a Covid booster shot generated a promising immune response against variants first identified in South Africa and Brazil. U.S. health officials said earlier Wednesday that highly contagious variants remain a "wild card" heading into the summer.

4. U.S. backs waiving patent protections for Covid vaccines

The Biden administration said Wednesday it supports waiving intellectual property protections for Covid vaccines, as other countries around the world struggle to manufacture the life-saving doses. Pfizer CEO Albert Bourla told CNBC on Tuesday that such a move would not impact the production of its Covid vaccine. "Bottlenecks are raw materials as raw materials are coming into manufacturing plants," he said. India again reported record daily new Covid cases. According to The New York Times, India has only fully vaccinated 2% of its 1.3 billion citizens compared with more than 30% in the U.S.

5. SEC chair to testify on short-selling, derivatives after GameStop, Archegos gyrations

Gary Gensler, who was sworn in last month as SEC chairman, will testify Thursday at a House Financial Services Committee on the GameStop saga and Archegos meltdown. According to prepared testimony, Gensler will tell lawmakers his agency is considering measures to require big investors to disclose more about their short positions, which played into January's GameStop frenzy, as well as their use of derivatives, which felled Archegos. In addition, Gensler will talk about how stock trading apps entice retail customers using game-like features such as points, rewards, bonuses and competitions.

— Reuters contributed to this report. Follow all the market action like a pro on CNBC Pro. Get the latest on the pandemic with CNBC's coronavirus coverage.