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

• S&P 500 set to drop on anniversary of stock bull market
• Yellen, Powell to testify on Capitol Hill on economic recovery
• AstraZeneca addresses U.S. concern about vaccine trial data
• Covid cases rise in parts of U.S. as some states relax restrictions
• Biden considers $3 trillion package for infrastructure

1. S&P 500 set to drop on anniversary of stock bull market

U.S. stock futures were mostly lower Tuesday after the Dow Jones Industrial Average and S&P 500 broke two-session losing streaks. Nasdaq futures rose modestly Tuesday, one day after the index logged a second straight session of gains, recovering about half of Thursday's 3% decline. Tech stocks benefited over the past two sessions from the 10-year Treasury yield retreating from last week's 14-month high.

Tuesday marks one year since the Covid low in the stock market, which ended the fastest bear market ever and ushered in another bull market. The S&P 500 has gained 76% since the March 23, 2020, close of 2,237. Over the past year, two presidents, Congress and the Federal Reserve put extraordinary fiscal and monetary policies in place to support the economy during the pandemic.

2. Yellen, Powell to testify on Capitol Hill on economic recovery

Fed Chairman Jerome Powell and Treasury Secretary Janet Yellen testify Tuesday before the House Financial Services Committee on the economy at noon ET. Yellen, who was Powell's predecessor, said she sees both growth and possibly full employment next year and credits President Joe Biden's Covid relief package. Powell's prepared remarks struck a cautiously optimistic tone, saying the economy is "much improved" but the recovery is "far from complete." Last week, after its March meeting, the Fed forecasted higher growth and inflation, while saying interest rates will likely remain near zero through 2023.

3. AstraZeneca addresses U.S. concern about vaccine trial data

AstraZeneca said Tuesday it will work with an independent group of U.S. health advisors who expressed concern about possible outdated information in the U.K. drugmaker's Covid vaccine trial results. AstraZeneca said it would "issue results of the primary analysis within 48 hours."

White House chief medical advisor Dr. Anthony Fauci told ABC News on Tuesday that AstraZeneca's inoculation is "likely a very good vaccine." However, he added, U.S. health advisors became concerned that data in AstraZeneca's public statement was "somewhat outdated and might, in fact, be misleading a bit."

The questions came one day after the company said a late-stage trial in U.S. and Latin America showed 79% efficacy for its two-shot regimen. AstraZeneca's vaccine also faced recent trouble in Europe, with a number of nations there temporarily suspending the use of the inoculation following reports of blood clots.

4. Covid cases rise in parts of U.S. as some states relax restrictions

Covid cases are once again on the rise across more than half of the U.S. as health officials warn about reopening too soon and race to vaccinate more people before highly contagious strains become prevalent in the country. As of Sunday, the seven-day average of new cases rose by 5% or more in 27 states, according to a CNBC analysis of data compiled by Johns Hopkins University. Across the U.S., the nation logged an average of 54,308 new cases per day over the past week, a 1% rise from the prior week after months of rapidly declining case numbers.

5. Biden considers $3 trillion package for infrastructure

Biden is assembling the next big White House priority, a $3 trillion infrastructure package. That would be on top of his recently signed $1.9 trillion coronavirus stimulus. The president met privately late Monday with Senate Democrats as Congress has already begun laying the groundwork with legislation for developing roads, hospitals and green energy systems as part of Biden's "Build Back Better" campaign promise. While the goal is a bipartisan package, Democrats in Congress have signaled a willingness to go it alone if they're blocked by Republicans.

— The Associated Press and Reuters contributed to this report. Get the latest on the pandemic with CNBC's coronavirus blog.