Brand name · Interferon beta-1a
Avonex: adverse event reports filed with FDA
116,302 reports list it as a suspect or interacting product, 2004–2026. Class: Interferon beta. Also reported as Avonex /05982701/.
- 116,302
- reports as suspect product
- 0.6% of all reports · about 5,170 a year
- 837
- reports, 12 months to June 2026
- 1,152 in the 12 months before
- 51.1%
- marked serious by the reporter
- 57.9% across the class
- 5.7%
- record death among outcomes, as reported
- 6,609 reports · not verified by FDA
116,302 adverse event reports received by FDA list the brand name Avonex (interferon beta-1a) as a suspect or interacting product, from January 2004 to June 2026. A further 25,603 reports list it only as a concomitant medication, and those are not counted in the figures on this page.
In the 12 months to June 2026, 837 reports listed it, down 27% from 1,152 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 5,170 reports a year and 0.6% of the 20,646,523 reports in the database, and 65.6% of the reports for the interferon beta class. How many people take it is not in the data, so a count is not a rate of occurrence.
Reporters most often recorded influenza like illness (8.5%), multiple sclerosis relapse (7.9%) and fall (5.8%). A report can list several reactions, so shares add to more than 100%; 3,311 different terms appear across these reports. Influenza like illness is recorded in 8.5% of these reports, about the same share as in the median interferon beta drug (8.4%).
51.1% of the reports are marked serious by the reporter (57.9% across the class); 5.7% record death among the outcomes and 34.6% record hospitalisation, as reported. 74.3% of the reports came from consumers, and the largest patient age group is 45 to 64 (33.1%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Avonex reports recording the termmedian drug in interferon beta
- Influenza like illnessflu-like symptoms8.5%9,828
- Multiple sclerosis relapsea flare of multiple sclerosis7.9%9,147
- Falla fall5.8%6,795
- Multiple sclerosis5.3%6,208
- Memory impairmentmemory problems5%5,844
- Gait disturbancedifficulty walking4.7%5,459
- Fatiguetiredness4.7%5,435
- Painpain, site not specified4.1%4,810
- Headachehead pain3.7%4,304
- Injection site painpain where the injection was given3.2%3,720
- Deaththe patient died; cause not stated by this term3.1%3,612
- Astheniaweakness or lack of energy2.9%3,315
- Anxietyanxiety2.7%3,147
- Pyrexiafever2.7%3,095
- Pain in extremitypain in an arm or leg2.6%3,049
- Hypoaesthesianumbness2.6%3,046
- Depressionlow mood2.6%3,018
- Balance disorderproblems with balance2.4%2,767
- Malaisegeneral feeling of being unwell2.3%2,681
- Injection site haemorrhagebleeding where the injection was given2.2%2,606
- Mobility decreasedreduced ability to move about2.2%2,594
- Drug ineffectivethe medicine did not work as expected2.2%2,504
- Tremorshaking2.1%2,488
- Pneumonialung infection2.1%2,420
- Stressstress2%2,281
- Chillschills or shivering1.9%2,262
- Muscular weaknessmuscle weakness1.9%2,191
- Drug dose omissiona dose was missed1.8%2,144
- Feeling abnormalfeeling odd or not right1.8%2,064
- Urinary tract infectionbladder or urinary infection1.8%2,055
Top 30 of 3,311 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 5 drugs in the interferon beta class; it describes the reports, not the patients. 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."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 177,168 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 89.2% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Multiple sclerosis | 101,279 | 87.1% |
| Relapsing-remitting multiple sclerosis | 1,909 | 1.6% |
| Maternal exposure timing unspecified | 286 | 0.2% |
| Relapsing multiple sclerosis | 123 | 0.1% |
| Drug exposure during pregnancy | 114 | 0.1% |
| Secondary progressive multiple sclerosis | 38 | 0% |
The indication field is filled in by the reporter and is often blank; shares are of all 116,302 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Avonex reports |
|---|---|---|
| Baclofen | 2,372 | 2% |
| Tecfidera | 2,315 | 2% |
| Ampyra | 2,199 | 1.9% |
| Tysabri | 1,943 | 1.7% |
| Gabapentin | 1,473 | 1.3% |
| Aspirin | 1,339 | 1.2% |
| Copaxone | 1,296 | 1.1% |
| Avonex Pen | 1,279 | 1.1% |
| Vitamin d | 1,116 | 1% |
| Ibuprofen | 1,026 | 0.9% |
Other products listed in reports where Avonex is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.
In context
| Measure | Avonex | Interferon beta | All reports |
|---|---|---|---|
| Reports as suspect product | 116,302 | 177,168 | 20,646,523 |
| Share of that pool | — | 65.6% | 0.6% |
| Reports, latest 12 months | 837 | — | 1,332,454 |
| Marked serious | 51.1% | 57.9% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 57 | 55 | 91 |
| Hospitalisation recorded, per 1,000 reports | 346 | 346 | 213 |
| Consumer-filed share | 74.3% | 68.2% | 45.8% |
| Top term, share of reports | Influenza like illness 8.5% | median 8.4% | 0.4% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. 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."
Other drugs in the interferon beta class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Rebif | brand | 43,252 | 456 | 79.6% |
| Plegridy | brand | 12,695 | 418 | 42.9% |
| Avonex Pen | brand | 4,155 | 0 | 64.1% |
| Interferon beta-1a | generic | 764 | 62 | 89.5% |
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." A brand and its generic are separate rows because reporters name them separately.
Questions about Avonex reports
How many adverse event reports has FDA received for Avonex?
116,302 reports list Avonex as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 837 of them arrived in the latest 12 months. Another 25,603 list it only as a concomitant medication.
What reactions are recorded in Avonex reports?
influenza like illness (8.5%), multiple sclerosis relapse (7.9%), fall (5.8%), multiple sclerosis (5.3%) and memory impairment (5%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Avonex was responsible.
How serious are the reports?
51.1% are marked serious by the reporter. Among the outcomes recorded, 5.7% of reports include death and 34.6% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
consumer or non-health professional (74.3%), physician (15.2%) and other health professional (5.4%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Avonex rising?
837 reports in the 12 months to June 2026, down 27% from 1,152 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Avonex was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Avonex?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. 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 report counts here when it lists Avonex as a suspect or interacting product; reports listing it only as a concomitant medication (25,603) are excluded. 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.