Jan 29 (Reuters) - Wall Street’s main indexes opened lower on Friday after COVID-19 vaccine data from Johnson & Johnson hurt sentiment and added to worries over a growing standoff between hedge funds and retail investors. The Dow Jones Industrial Average fell 49.5 points, or 0.16%, at the open to 30553.91, the S&P 500 fell 9.3 points, or 0.25%, at the open to 3778.05, while the Nasdaq Composite dropped 52.4 points, or 0.39%, to 13284.719 at the opening bell. (Reporting by Devik Jain in Bengaluru; Editing by Shounak Dasgupta)