What happened

Shares of Moderna (MRNA -0.74%) were rising 2.6% higher as of 11:25 a.m. EDT on Tuesday. The gain came after the company announced that the European Medicines Agency authorized a third dose of COVID-19 vaccine Spikevax to severely immunocompromised individuals ages 12 and older.

So what

The modest gain for the vaccine stock today reflects the muted impact that the EMA decision will make for Moderna. Authorizing the third dose for only severely immunocompromised individuals limits the market significantly.

A gloved hand holding a syringe in front of a European Union flag with gold stars in a circle on a blue background.

Image source: Getty Images.

More importantly, the European Union has already placed orders for a total 460 million doses of Spikevax. So far, around 92.2 million doses of Moderna's COVID-19 vaccine have been distributed to EU countries. The EU's supply agreements to date will more than cover the additional doses needed under the latest EMA authorization.

Now what

The most important thing to watch with Moderna going forward isn't authorizations and approvals for its COVID-19 vaccine but is instead additional supply agreements. New deals, especially any that include firm order commitments for beyond 2022, could provide the biggest catalysts for the stock.