Wall Street's main stock indexes rallied Wednesday after the Federal Reserve eased investor jitters by keeping borrowing costs unchanged and reinforcing expectations that rates could be cut by three-quarters of a percentage point by the end of 2024.

The Fed's policy statement described inflation as remaining "elevated," and it updated quarterly economic projections to forecast growth of 2.1% for the year versus 1.4% projected in December and an unemployment rate ending the year at 4%, lower than the 4.1% anticipated in December.

Stocks added to gains after Fed Chair Jerome Powell said in a press conference that despite recent inflation data coming in hotter than expected, the numbers "haven't really changed the overall story, which is that of inflation moving down gradually, on a somewhat bumpy road."

Strategists said Wall Street was reassured by Powell's comments.

"He said he wasn't trying to dismiss any data but he kind of gave the market a reason they could use to dismiss the data," said Alex Coffey, senior trading strategist at TD Ameritrade.

"We came in to this day feeling Jerome Powell might push back on market expectations or pivot away from dovish expectations since December because of the data we've had in the last two months," said Coffey. "While he didn't necessarily go full dove, it was dovish versus recent market worries."

According to preliminary data, the S&P 500 gained 44.78 points, or 0.89%, to end at 5,223.29 points, while the Nasdaq Composite gained 202.22 points, or 1.25%, to 16,369.01. The Dow Jones Industrial Average rose 398.29 points, or 1.02%, to 39,509.05.

Most of the S&P's 11 major sectors gained ground.

The healthcare sector was under pressure during the session partly due to COVID-19 vaccine makers. U.S.-listed shares of BioNTech dropped after it reported a 2023 revenue and earnings plunge as it shifted focus to cancer drug development.

Shares of COVID-19 vaccine makers Moderna and Novavax both eased.

Boosting the consumer discretionary sector, Tesla gained after confirming to Reuters that it will raise the price of its China-produced Model Y vehicles by 5,000 yuan ($694.55) from April 1.

Equinix shares eased after Hindenburg Research said it has taken a short position in the data center operator.

Chipotle Mexican Grill shares climbed after the company said its board had approved a 50-for-1 split of its common stock.