CAMBRIDGE, Mass. (AP) — Moderna has begun testing an omicron-specific version of its COVID-19 vaccine in healthy adults.

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Moderna announced the study Wednesday.

Earlier this week, competitor Pfizer began similar research with its reformulated shots. It's not clear that global health authorities will decide the vaccines need to be changed.

The shots still offer strong protection against death and severe disease, and a booster also improves the chances of avoiding even a milder infection.

The newest study will give an omicron-matched booster to about 600 people who've already received either two or three Moderna shots already.

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