What the label lists and what reports show
Interferon beta 1a side effects
Interferon beta 1a's FDA label: “The most common adverse reactions in controlled clinical trials were injection site disorders, influenza-like symptoms, abdominal pain, depression, elevation of liver enzymes and hematologic abnormalities ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact …” FAERS holds 192,061 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is multiple sclerosis relapse (15,855 reports).
- No generic listed
Check it at the source: the interferon beta 1a FDA label on DailyMed (effective September 22, 2025, EMD Serono, Inc.); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of REBIF?REBIF may cause serious side effects, including: See " What is the most important information I should know about REBIF? " Blood problems. REBIF can affect your bone marrow and cause low red and white blood cell, and platelet counts. In some people, these blood cell counts may fall to dangerously low levels. If your blood cell counts become very low, you can get infections and problems with bleeding and bruising. Your healthcare provider may ask you to have regular blood tests to check for blood problems. Pulmonary arterial hypertension. Pulmonary arterial hypertension can occur with interferon beta products, including REBIF. Symptoms may include new fatigue or shortness of breath. Contact your healthcare provider right away if you develop these symptoms. Seizures. Some people have had seizures while taking REBIF. The most common side effects of REBIF include: flu-like symptoms. […]
Source: FDA drug label, EMD Serono, Inc., effective September 22, 2025 (SPL set c6fcb5d2-8fcd-44fa-a838-b84ee5f44f0f), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common adverse reactions in controlled clinical trials were injection site disorders, influenza-like symptoms, abdominal pain, depression, elevation of liver enzymes and hematologic abnormalities ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact EMD Serono at 1-800-283-8088 ext.
Table 3. Adverse Reactions and Laboratory Abnormalities in Study 1
| Body System Preferred Term | Placebo tiw (n=187) % | REBIF 22 mcg tiw (n=189) % | REBIF 44 mcg tiw (n=184) % |
|---|---|---|---|
| Influenza-like symptoms | 51 | 56 | 59 |
| Headache | 63 | 65 | 70 |
| Fatigue | 36 | 33 | 41 |
| Fever | 16 | 25 | 28 |
| Rigors | 5 | 6 | 13 |
| Chest pain | 5 | 6 | 8 |
| Malaise | 1 | 4 | 5 |
| Injection Site Reaction | 39 | 89 | 92 |
| Injection Site Necrosis | 0 | 1 | 3 |
| Hypertonia | 5 | 7 | 6 |
| Coordination Abnormal | 2 | 5 | 4 |
| Convulsions | 2 | 5 | 4 |
| Somnolence | 1 | 4 | 5 |
| Thyroid Disorder | 3 | 4 | 6 |
| Abdominal Pain | 17 | 22 | 20 |
| Dry Mouth | 1 | 1 | 5 |
| SGPT Increased | 4 | 20 | 27 |
| SGOT Increased | 4 | 10 | 17 |
| Bilirubinemia | 1 | 3 | 2 |
| Myalgia | 20 | 25 | 25 |
| Back Pain | 20 | 23 | 25 |
| Skeletal Pain | 10 | 15 | 10 |
| Leukopenia | 14 | 28 | 36 |
| Lymphadenopathy | 8 | 11 | 12 |
| Thrombocytopenia | 2 | 2 | 8 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following adverse reactions are discussed in more detail in the Warnings and Precautions section of the label: Depression and Suicide [see Warnings and Precautions (5.1) ] Hepatic Injury [see Warnings and Precautions (5.2) ] Anaphylaxis and Other Allergic Reactions [see Warnings and Precautions (5.3) ] Injection Site Reactions including Necrosis [see Warnings and Precautions (5.4) ] Decreased Peripheral Blood Counts [see Warnings and Precautions (5.5) ] Thrombotic Microangiopathy [see Warnings and Precautions (5.6) ] Pulmonary Arterial Hypertension [ see Warnings and Precautions (5.7) ] Seizures [see Warnings and Precautions (5.8) ] Laboratory Tests [see Warnings and Precautions (5.9) ] The most common adverse reactions in controlled clinical trials were injection site disorders, influenza-like symptoms, abdominal pain, depression, elevation of liver enzymes and hematologic abnormalities ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact EMD Serono at 1-800-283-8088 ext. 5563 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch 6.1 Clinical Trial Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of REBIF cannot be directly compared to rates in the clinical trials of other drugs and may not reflect the rates observed in practice. …
Source: FDA drug label, EMD Serono, Inc., effective September 22, 2025 (SPL set c6fcb5d2-8fcd-44fa-a838-b84ee5f44f0f), via openFDA; the full label on DailyMed
What do FAERS reports show?
192,061 reports list interferon beta 1a among the medicines taken, each a report of something that happened, not proof the medicine caused it; 9,782 are coded as a death and 61,393 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Interferon beta 1a: the full record
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