Moderna dominates Wall St trading ahead of S&P 500 debut

July 20 (Reuters) - Moderna’s stock tumbled in a volatile session on Tuesday, with the COVID-19 vaccine maker the most heavily traded company on Wall Street ahead of its debut in the S&P 500 on Wednesday.

Over $17 billion worth of the company’s shares had been exchanged by mid-afternoon, nearly nine times more than its $2 billion average over the past six months, according to Refinitiv data.

Apple was second-busiest stock during the session, with about $10 billion worth of its shares traded. Moderna joins the S&P 500 as of the start of trading on Wednesday. That means index funds managing over $5 trillion will have to buy about 17% of the company’s stock by Tuesday’s close, according to Howard Silverblatt, a senior index analyst at S&P Dow Jones Indices.

Moderna’s inclusion in the index also means that actively managed funds that measure their performance against the S&P 500 are more likely to consider buying its shares.

Moderna was last down 5% for the session after surging 9% to a record high earlier in the day. The stock has gained about 14% since July 15, when S&P Dow Jones Indices announced its addition to the S&P 500.

The latest volatility in Moderna’s stock comes as concerns increase over the highly contagious Delta variant of COVID-19, now responsible for the majority of new infections. Fears about a resurgence in the virus slammed Wall Street on Monday.

Fueled by the success of its COVID-19 vaccine, Moderna’s stock has rallied almost 200% so far in 2021. (Reporting by Noel Randewich; Editing by Lisa Shumaker)