Moody's affirmed Shire PLC's Baa3 issuer rating.

The rating agency revised the outlook on the rating to positive from stable, representing its expectations for solid operating performance from recent product launches and continuing debt reduction.

Moody's said the Baa3 rating reflects the company's $15 billion revenue base and its strong placement in the market in the fields of hemophilia, immunology, and neuroscience.

The agency believes the Irish company's focus on products that treat rare diseases is positive. Drugs for such conditions are expensive, critical for patients and have very high barriers to entry, according to Moody's.