Peginterferon Beta-1A side effects: what 13,015 FDA adverse event reports show

Peginterferon Beta-1A · Plegridy, Plegridy Pen · 995 reaction terms · 35,477 drug–reaction co-reports · data 2026-09-14

Drug class

Interferon beta

FDA label (Established Pharmacologic Class)

Brand names

Plegridy, Plegridy Pen

openFDA label

Who reports

13,015 reports · 43% serious · 333 with death outcome · 82% female

openFDA FAERS counts, all years, deduplication not applied

Used for

PLEGRIDY is indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults. PLEGRIDY is an interferon beta indicated f.

FDA label, Indications and Usage

What it is

Peginterferon beta-1a is a covalent conjugate of recombinant interferon beta-1a (approximate molecular weight [MW] 20,000 daltons) with a single, linear methoxy poly(ethyleneglycol)-O-2-methylpropionaldehyde molecule (approximate MW 20,000 daltons).

FDA label, Description section

Boxed warning

None in the current label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 40 strongest signals

Labeled adverse reaction 5Labeled (related wording) 11Likely indication confounding 2Reporting / coding artifact 5Not in label — unassessed 17

What the badges mean

Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.

Strongest disproportionality signals

Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 955 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Drug delivery system malfunction	462	161.9 147.4–177.9ROR 167.8 · χ² 66,915 / p <1e-300	146.1 EB05 135.3 · IC025 +6.8 3/3 methods agree	Not in label — unassessed	serious n=7 · 94% consumer	no trial data cached
Needle fatigue	22	81.2 52.9–124.6ROR 81.3 · χ² 1,582 / p <1e-300	72.6 EB05 50.5 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious n=4 · 73% consumer	no trial data cached
Procedural anxiety	24	59.0 39.3–88.7ROR 59.2 · χ² 1,265 / p 2e-277	54.6 EB05 38.6 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious n=9	no trial data cached
Prolonged labour	19	51.4 32.5–81.1ROR 51.4 · χ² 861 / p 2e-189	47.6 EB05 32.2 · IC025 +3.7 3/3 methods agree	Not in label — unassessed	serious n=19	no trial data cached
Puncture site haemorrhage	20	46.9 30.1–73.1ROR 47.0 · χ² 828 / p 2e-182	43.8 EB05 29.9 · IC025 +3.7 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Injection site dryness	21	39.1 25.4–60.3ROR 39.2 · χ² 724 / p 7e-160	37.0 EB05 25.5 · IC025 +3.6 3/3 methods agree	Labeled (related wording) related wording	90% consumer	no trial data cached
Cutaneous symptom	15	36.9 22.1–61.6ROR 36.9 · χ² 478 / p 4e-106	34.6 EB05 22.3 · IC025 +3.2 3/3 methods agree	Labeled (related wording) related wording	serious n=4	no trial data cached
Hemianaesthesia	16	32.5 19.8–53.3ROR 32.6 · χ² 448 / p 8e-100	30.8 EB05 20.1 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Influenza like illness (flu-like illness)	1,464	29.0 27.6–30.5ROR 32.6 · χ² 39,007 / p <1e-300	28.5 EB05 27.3 · IC025 +4.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 19.5 · 77% consumer	no trial data cached
Magnetic resonance imaging abnormal	18	25.0 15.7–39.8ROR 25.0 · χ² 385 / p 6e-86	24.0 EB05 16.0 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious n=12	no trial data cached
Multiple sclerosis relapse	971	22.9 21.6–24.4ROR 24.7 · χ² 20,105 / p <1e-300	22.6 EB05 21.4 · IC025 +4.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 30.1 · 76% consumer	no trial data cached
Vaccination complication	11	21.6 11.9–39.2ROR 21.6 · χ² 194 / p 3e-44	20.3 EB05 11.6 · IC025 +2.5 3/3 methods agree	Reporting / coding artifact	serious n=3	no trial data cached
Loss of control of legs	48	20.4 15.4–27.2ROR 20.5 · χ² 858 / p 8e-189	20.1 EB05 15.7 · IC025 +3.6 3/3 methods agree	Not in label — unassessed	serious n=27 · 79% consumer	no trial data cached
General symptom	91	19.6 16.0–24.1ROR 19.8 · χ² 1,572 / p <1e-300	19.3 EB05 16.2 · IC025 +3.8 3/3 methods agree	Labeled (related wording) related wording	serious n=29 · 73% consumer	no trial data cached
Multiple sclerosis	562	19.0 17.5–20.6ROR 19.8 · χ² 9,489 / p <1e-300	18.8 EB05 17.5 · IC025 +4.1 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 15.6 · 80% consumer	no trial data cached
Breech presentation	14	18.1 10.7–30.6ROR 18.1 · χ² 207 / p 3e-47	17.1 EB05 10.3 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=14	no trial data cached
Secondary progressive multiple sclerosis	21	18.0 11.7–27.7ROR 18.0 · χ² 317 / p 3e-71	17.4 EB05 11.8 · IC025 +2.9 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious n=11 · 86% consumer	no trial data cached
Band sensation	14	17.8 10.5–30.2ROR 17.8 · χ² 203 / p 2e-46	16.9 EB05 10.1 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=5	no trial data cached
Nuclear magnetic resonance imaging abnormal	33	15.9 11.3–22.5ROR 16.0 · χ² 443 / p 1e-98	15.6 EB05 11.4 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious n=18	no trial data cached
Lack of injection site rotation	16	15.1 9.2–24.7ROR 15.1 · χ² 195 / p 2e-44	14.1 EB05 8.6 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious n=7	no trial data cached
Injection site erythema (redness where injected)	1,061	13.9 13.2–14.8ROR 15.1 · χ² 12,699 / p <1e-300	13.8 EB05 13.1 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 22.6 · 81% consumer	no trial data cached
Device malfunction	572	13.8 12.7–15.0ROR 14.4 · χ² 6,746 / p <1e-300	13.7 EB05 12.8 · IC025 +3.6 3/3 methods agree	Reporting / coding artifact	serious PRR 4.4 · 90% consumer	no trial data cached
Injection site reaction	578	13.7 12.6–14.8ROR 14.2 · χ² 6,734 / p <1e-300	13.5 EB05 12.6 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 14.6 · 76% consumer	no trial data cached
Injection site indentation	17	13.5 8.4–21.8ROR 13.5 · χ² 183 / p 5e-42	12.5 EB05 7.7 · IC025 +2.5 3/3 methods agree	Labeled (related wording) related wording	–	no trial data cached
Injection site cellulitis	14	12.3 7.3–20.9ROR 12.3 · χ² 134 / p 3e-31	10.9 EB05 6.3 · IC025 +2.2 3/3 methods agree	Labeled (related wording) related wording	serious n=4	no trial data cached
Motor dysfunction	74	11.9 9.4–14.9ROR 11.9 · χ² 719 / p 9e-159	11.6 EB05 9.5 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 11.0 · 91% consumer	no trial data cached
Haemorrhage in pregnancy	10	11.3 6.0–21.0ROR 11.3 · χ² 83 / p 4e-20	9.1 EB05 4.7 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious n=10	no trial data cached
Injection site inflammation	34	11.1 8.0–15.6ROR 11.2 · χ² 302 / p 7e-68	10.5 EB05 7.7 · IC025 +2.7 3/3 methods agree	Labeled (related wording) related wording	serious n=9 · 74% consumer	no trial data cached
Central nervous system lesion	95	11.1 9.1–13.6ROR 11.2 · χ² 860 / p 3e-189	10.9 EB05 9.1 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 11.6 · 77% consumer	no trial data cached
Injection site scar	19	10.9 7.0–17.1ROR 10.9 · χ² 160 / p 5e-37	9.8 EB05 6.3 · IC025 +2.3 3/3 methods agree	Labeled (related wording) related wording	–	no trial data cached
Injection site infection	22	10.9 7.2–16.6ROR 10.9 · χ² 187 / p 9e-43	9.9 EB05 6.6 · IC025 +2.4 3/3 methods agree	Labeled (related wording) related wording	serious n=5 · 86% consumer	no trial data cached
Injection site rash	195	10.4 9.0–12.0ROR 10.5 · χ² 1,639 / p <1e-300	10.3 EB05 9.1 · IC025 +3.1 3/3 methods agree	Labeled adverse reaction exact term	serious n=37 · 78% consumer	no trial data cached
Injection site warmth	126	9.9 8.3–11.8ROR 10.0 · χ² 994 / p 2e-218	9.7 EB05 8.3 · IC025 +3.0 3/3 methods agree	Labeled adverse reaction exact term	serious n=20 · 89% consumer	no trial data cached
Adverse reaction	81	9.9 7.9–12.3ROR 9.9 · χ² 634 / p 3e-140	9.6 EB05 7.9 · IC025 +2.9 3/3 methods agree	Reporting / coding artifact	serious n=11	no trial data cached
Injection site discolouration	74	9.7 7.7–12.1ROR 9.7 · χ² 562 / p 1e-124	9.3 EB05 7.6 · IC025 +2.8 3/3 methods agree	Labeled (related wording) related wording	serious n=15 · 84% consumer	no trial data cached
Trigeminal neuralgia	22	8.8 5.8–13.4ROR 8.8 · χ² 144 / p 1e-33	7.8 EB05 5.3 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious n=14 · 86% consumer	no trial data cached
Optic neuritis	48	8.5 6.4–11.3ROR 8.5 · χ² 309 / p 2e-69	8.0 EB05 6.2 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.7 · 70% consumer	no trial data cached
Frustration tolerance decreased	41	8.2 6.1–11.2ROR 8.3 · χ² 252 / p 4e-57	7.7 EB05 5.8 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious n=4 · 85% consumer	no trial data cached
Monoplegia	22	8.1 5.4–12.4ROR 8.2 · χ² 130 / p 2e-30	7.2 EB05 4.9 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious n=21 · 86% consumer	no trial data cached
Injection site hypersensitivity	15	7.9 4.7–13.1ROR 7.9 · χ² 83 / p 4e-20	6.6 EB05 4.2 · IC025 +1.8 3/3 methods agree	Labeled (related wording) related wording	–	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

Most frequently reported reactions

By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Influenza like illness (flu-like illness)	1,464	29.0 27.6–30.5ROR 32.6 · χ² 39,007 / p <1e-300	28.5 EB05 27.3 · IC025 +4.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 19.5 · 77% consumer	no trial data cached
Injection site erythema (redness where injected)	1,061	13.9 13.2–14.8ROR 15.1 · χ² 12,699 / p <1e-300	13.8 EB05 13.1 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 22.6 · 81% consumer	no trial data cached
Multiple sclerosis relapse	971	22.9 21.6–24.4ROR 24.7 · χ² 20,105 / p <1e-300	22.6 EB05 21.4 · IC025 +4.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 30.1 · 76% consumer	no trial data cached
Fatigue (tiredness)	713	1.5 1.4–1.6ROR 1.5 · χ² 114 / p 8e-27	1.5 EB05 1.4 · IC025 +0.4	Labeled adverse reaction exact term	serious PRR 1.4 · 83% consumer	no trial data cached
Headache	616	1.6 1.5–1.7ROR 1.6 · χ² 136 / p 1e-31	1.6 EB05 1.5 · IC025 +0.5	Labeled adverse reaction exact term	serious PRR 1.5 · 81% consumer	no trial data cached
Pain	607	1.6 1.5–1.7ROR 1.6 · χ² 135 / p 1e-31	1.6 EB05 1.5 · IC025 +0.5	Labeled adverse reaction exact term	serious PRR 1.1 · 83% consumer	no trial data cached
Injection site reaction	578	13.7 12.6–14.8ROR 14.2 · χ² 6,734 / p <1e-300	13.5 EB05 12.6 · IC025 +3.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 14.6 · 76% consumer	no trial data cached
Device malfunction	572	13.8 12.7–15.0ROR 14.4 · χ² 6,746 / p <1e-300	13.7 EB05 12.8 · IC025 +3.6 3/3 methods agree	Reporting / coding artifact	serious PRR 4.4 · 90% consumer	no trial data cached
Multiple sclerosis	562	19.0 17.5–20.6ROR 19.8 · χ² 9,489 / p <1e-300	18.8 EB05 17.5 · IC025 +4.1 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 15.6 · 80% consumer	no trial data cached
Pyrexia (fever)	520	2.4 2.2–2.6ROR 2.5 · χ² 438 / p 1e-97	2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 1.7 · 79% consumer	no trial data cached
Memory impairment	472	5.5 5.1–6.1ROR 5.7 · χ² 1,756 / p <1e-300	5.5 EB05 5.1 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 2.5 · 91% consumer	no trial data cached
Malaise (feeling unwell)	468	1.7 1.6–1.9ROR 1.7 · χ² 141 / p 7e-33	1.7 EB05 1.6 · IC025 +0.6	Not in label — unassessed	serious PRR 1.4 · 82% consumer	no trial data cached
Drug delivery system malfunction	462	161.9 147.4–177.9ROR 167.8 · χ² 66,915 / p <1e-300	146.1 EB05 135.3 · IC025 +6.8 3/3 methods agree	Not in label — unassessed	serious n=7 · 94% consumer	no trial data cached
Injection site pain (pain where injected)	447	2.4 2.2–2.6ROR 2.4 · χ² 358 / p 4e-80	2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.1 · 83% consumer	no trial data cached
Fall	437	2.1 1.9–2.3ROR 2.2 · χ² 260 / p 8e-59	2.1 EB05 2.0 · IC025 +0.9	Not in label — unassessed	serious PRR 2.3 · 80% consumer	no trial data cached

Unlabeled candidate signals

These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.

Drug delivery system malfunction — n=462, PRR 161.9
Needle fatigue — n=22, PRR 81.2
Procedural anxiety — n=24, PRR 59.0
Puncture site haemorrhage — n=20, PRR 46.9
Loss of control of legs — n=48, PRR 20.4
Motor dysfunction — n=74, PRR 11.9
Central nervous system lesion — n=95, PRR 11.1
Trigeminal neuralgia — n=22, PRR 8.8
Optic neuritis — n=48, PRR 8.5
Frustration tolerance decreased — n=41, PRR 8.2

Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.

Common questions

What are the most reported side effects of Peginterferon Beta-1A?

In FDA FAERS, the most frequently co-reported reaction terms for Peginterferon Beta-1A are influenza like illness, injection site erythema, multiple sclerosis relapse, fatigue, headache, pain. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.

Does Peginterferon Beta-1A have an FDA boxed warning?

No. The FDA label retrieved for Peginterferon Beta-1A has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Peginterferon Beta-1A causes these side effects?

No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.

Sources & methods

FDA label via openFDA (set ID 08f0ea03-4e6d-195d-aef4-886e32befa95, effective 20251112; matched on openfda.generic_name.exact:"PEGINTERFERON BETA-1A")
Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA count= aggregation, field patient.drug.openfda.generic_name.exact, 995 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction
Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
Seriousness and sex counts from openFDA count=serious, patient.patientsex, seriousnessdeath

Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.