NEW YORK: The Dow and the S&P 500 fell on Tuesday after a four-day winning streak as a pause in Johnson & Johnson's COVID-19 trial triggered concerns about the timing of a vaccine, although a rally in technology shares supported the Nasdaq. Johnson & Johnson shed 2% as it said it would take "a few days" to review its halted clinical trial following an unexplained illness in a study participant, possibly delaying results on one of the most closely watched efforts to contain the global pandemic.

Some of the worst-hit companies due to the pandemic - cruise line operators Carnival Corp, Norwegian Cruise Line Holdings and hotel operator Wynn Resorts Ltd - fell between 3% and 7%. Apple Inc slipped 1.1% ahead of a virtual event starting 1 p.m. ET (1700 GMT) where it is widely expected to unveil four new iPhone models.

Amazon.com Inc shares, which have already surged 86% this year, added 1% as the company began 48 hours of promotions as part of "Prime Day" in an early start to the holiday shopping season. At 12:28 p.m. ET, the Dow Jones Industrial Average was down 0.35% at 28,735.90 and the S&P 500 was down 0.31% at 3,523.23. The Nasdaq Composite was up 0.16% at 11,894.92.

Boeing Co dropped 2% as it lost another three orders for its grounded 737 MAX jet in September and delivered half the number of aircraft from the same month a year earlier.