# Safety & Tolerability
Keywords: PLEGRIDY, safety profile, tolerability, adverse events, injection site reactions, flu-like symptoms, multiple sclerosis, long-term study, ATTAIN, ADVANCE

> This page provides detailed information about the safety and tolerability of PLEGRIDY, a treatment for multiple sclerosis, including its long-term safety profile, common adverse events, and findings from clinical studies.

## Details
- [Safety and tolerability](#): PLEGRIDY has a well-established safety profile observed in studies up to 5 years, with most adverse events reported as mild to moderate.
- [Adverse events](#): The most common adverse events include injection site reactions, flu-like symptoms, and headache, with serious adverse events reported in a smaller percentage of patients.
- [Long-term safety profile](#): Findings from the ATTAIN study show consistent safety results over 6 years, with reduced adverse event rates in later years.
- [Injection site reactions (ISR)](#): ISRs were common but decreased significantly from 68% in the first 2 years to 43% in years 3-6.
- [Flu-like symptoms (FLS)](#): FLS were reported by 79% of patients in the first 2 years, decreasing to 62% in years 3-6, with the most common symptoms being influenza-like illness and pyrexia.
- [Adverse event reporting](#): Guidance is provided for reporting adverse events in the UK and Ireland, including contact information for Biogen and regulatory authorities.