Moderna to join S&P 500, shares jump after hours

Moderna Inc will join the S&P 500 index as of the start of trading on July 21, replacing Alexion Pharmaceuticals, S&P Dow Jones Indices said in a statement on Thursday.

Moderna shares rose 6% in extended trade after the announcement. The COVID-19 vaccine maker's stock has surged over 150% this year, elevating its market capitalization to about $100 billion.

Britain's AstraZeneca said last December it would acquire U.S. biotech Alexion in a $39 billion deal.