Pharmacologic class (EPC) · 5 drug pages

Interferon beta: adverse event reports filed with FDA

177,168 reports list a drug in this class as a suspect or interacting product, 2004–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

177,168
reports across the class: 0.9% of all reports; 1,773
reports, 12 months to June 2026: 2,261 in the 12 months before; 57.9%
marked serious by the reporter: 57.4% across all reports; 5
drugs with a page: brand and generic names counted separately

Interferon beta is a pharmacologic class (an FDA Established Pharmacologic Class) with 5 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 177,168 adverse event reports received by FDA, 0.9% of the database, from January 2004 to June 2026.

1,773 reports arrived in the 12 months to June 2026, down 22% from 2,261 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 57.9% of the class's reports are marked serious, 5.5% record death among the outcomes and 34.6% record hospitalisation, as reported.

Across the class the reactions recorded most often are multiple sclerosis relapse (8.2%), influenza like illness (8.1%) and fall (5.5%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
AvonexInterferon beta-1a	brand	116,302	837	51.1%	Influenza like illness
RebifInterferon beta-1a	brand	43,252	456	79.6%	Multiple sclerosis relapse
PlegridyPeginterferon beta-1a	brand	12,695	418	42.9%	Influenza like illness
Avonex PenInterferon beta-1a	brand	4,155	0	64.1%	Multiple sclerosis relapse
Interferon beta-1a	generic	764	62	89.5%	Multiple sclerosis relapse

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Multiple sclerosis relapsea flare of multiple sclerosis8.2%14,551
Influenza like illnessflu-like symptoms8.1%14,400
Falla fall5.5%9,718
Fatiguetiredness5.1%8,996
Multiple sclerosis4.9%8,645
Gait disturbancedifficulty walking4.2%7,492
Painpain, site not specified4.2%7,381
Headachehead pain4.1%7,335
Memory impairmentmemory problems4.1%7,240
Injection site painpain where the injection was given3.8%6,795
Astheniaweakness or lack of energy2.9%5,188
Deaththe patient died; cause not stated by this term2.9%5,091
Depressionlow mood2.9%5,064
Pyrexiafever2.8%5,046
Hypoaesthesianumbness2.7%4,869
Injection site erythemaredness where the injection was given2.7%4,811
Pain in extremitypain in an arm or leg2.5%4,487
Malaisegeneral feeling of being unwell2.4%4,241
Anxietyanxiety2.4%4,227
Balance disorderproblems with balance2.3%3,989
Urinary tract infectionbladder or urinary infection2.1%3,790
Drug ineffectivethe medicine did not work as expected2.1%3,768
Pneumonialung infection2.1%3,683
Nauseafeeling sick2.1%3,652
Dizzinesslight-headedness or unsteadiness2.1%3,651

Solid bar: share of all class reports. Hollow bar: the median share across the 5 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death5.5%9,784

Life-threatening0.7%1,221

Hospitalisation (initial or prolonged)34.6%61,246

Disability0.7%1,303

Congenital anomaly0.2%397

Other serious22.4%39,772

Not serious42.1%74,504

Patient age

Under 20.3%505

2 to 110.1%105

12 to 170.3%540

18 to 4418.2%32,261

45 to 6430.5%54,027

65 to 746.2%11,040

75 and over1.1%1,887

Age not given43.4%76,803

Who reported

Physician14.8%26,162

Pharmacist2%3,528

Other health professional8.1%14,324

Lawyer0%33

Consumer or non-health professional68.2%120,870

Not given6.9%12,251

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Interferon beta reports

Which drugs are in the Interferon beta class on this site?

Avonex, Rebif, Plegridy, Avonex Pen and Interferon beta-1a. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

177,168 reports through June 2026, 1,773 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

multiple sclerosis relapse (8.2%), influenza like illness (8.1%), fall (5.5%), fatigue (5.1%) and multiple sclerosis (4.9%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.