Recap

Moderna Joins the Nasdaq-100 as Warner Bros. Discovery Exits on the Paramount Merger

Moderna will join the Nasdaq-100 on October 9, replacing Warner Bros. Discovery as its pending $81 billion Paramount Skydance merger closes — a move driven by Moderna's 541% year-to-date stock surge and $75 billion valuation.

3 min read

Nasdaq said Thursday that Moderna ($MRNA) will join the Nasdaq-100 Index, replacing Warner Bros. Discovery ($WBD), effective before the market opens on Friday, October 9. The swap is part of a broader index shuffle triggered by Warner Bros. Discovery's pending $81 billion merger with Paramount Skydance.

Metric	Figure
Moderna 2026 YTD stock move	+541%
Moderna market value	~$75 billion
Nasdaq-100 effective date	Oct 9, 2026 (before open)
WBD-Paramount merger close	Expected Oct 6, 2026

Why Warner Bros. Discovery is leaving

Warner Bros. Discovery is exiting the Nasdaq-100, the S&P 500, and MSCI indexes as its $81 billion acquisition by Paramount Skydance is expected to close October 6, after a months-long delay. Once the deal closes, Warner Bros. Discovery will no longer trade as a standalone public company, and Paramount Skydance will shift its primary listing to the NYSE.

Why Moderna was selected

Moderna's shares have surged 541% year-to-date, making it the S&P 500's second-best-performing stock and lifting its market value to roughly $75 billion — comfortably within range of the Nasdaq-100's largest non-financial constituents. The rally has been fueled in large part by positive Phase 3 trial results for intismeran autogene, an investigational cancer vaccine Moderna is developing with Merck.

A parallel swap at the S&P 500

Warner Bros. Discovery's exit is also triggering a separate change at the S&P 500: Twilio ($TWLO) will replace WBD there, moving up from the S&P MidCap 400 effective before the open on October 6 — the same day the Paramount merger is expected to close. FormFactor will in turn take Twilio's vacated MidCap 400 spot. Twilio shares touched a 52-week high on the news, up more than 200% from their 52-week low.

Why it matters. Index inclusion forces funds that track the Nasdaq-100 and S&P 500 to buy the newly added stock and sell the one being removed, which can create real trading flows independent of either company's underlying fundamentals. For Moderna and Twilio, both already on strong run-ups this year, inclusion adds a fresh, mechanical source of buying pressure on top of the momentum that earned them a seat in the first place.

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