What the label lists and what reports show
Efgartigimod alfa side effects
Efgartigimod alfa's FDA label: “Most common adverse reactions (≥ 10%) in patients treated with gMG are respiratory tract infections, headache, and urinary tract infection.” FAERS holds 3,880 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 myasthenia gravis crisis (448 reports).
- No generic listed
Check it at the source: the efgartigimod alfa FDA label on DailyMed (effective May 13, 2026, argenx US); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsMost common adverse reactions (≥ 10%) in patients treated with gMG are respiratory tract infections, headache, and urinary tract infection.
Table 1: Adverse Reactions in ≥ 5% of Patients Treated with VYVGART and More Frequently than in Placebo-Treated Patients in Study 1 (Safety Population)
| Adverse reaction | VYVGART (N=84) % | Placebo (N=83) % |
|---|---|---|
| Respiratory tract infection | 33 | 29 |
| Headache Headache includes migraine and procedural headache. | 32 | 29 |
| Urinary tract infection | 10 | 5 |
| Paraesthesia Paraesthesia includes oral hypoesthesia, hypoesthesia, and hyperesthesia. | 7 | 5 |
| Myalgia | 6 | 1 |
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 clinically significant adverse reactions are described elsewhere in the labeling: Infections [see Warnings and Precautions (5.1) ] Hypersensitivity Reactions [see Warnings and Precautions (5.2) ] Infusion-Related Reactions [see Warnings and Precautions (5.3) ] Most common adverse reactions (≥ 10%) in patients treated with gMG are respiratory tract infections, headache, and urinary tract infection. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact argenx at 1-833-argx411 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. In clinical studies, the safety of VYVGART in adult patients with gMG has been evaluated in 364 patients who received at least one dose of VYVGART. In a placebo-controlled study (Study 1) in patients with gMG, 84 patients received VYVGART 10 mg/kg [see Clinical Studies (14) ]. Of these 84 patients, approximately 75% were female, 82% were White, 11% were Asian, and 8% were of Hispanic or Latino ethnicity. The mean age at study entry was 46 years (range 19 to 78). …
Source: FDA drug label, argenx US, effective May 13, 2026 (SPL set 8aefc8e3-26d6-4ff6-aab9-a7542927e084), via openFDA; the full label on DailyMed
What do FAERS reports show?
3,880 reports list efgartigimod alfa among the medicines taken, each a report of something that happened, not proof the medicine caused it; 372 are coded as a death and 1,888 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. Reports rose sharply in 2024 (1,668, against a median of 3 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 17 reactions below, 3 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?
- Efgartigimod alfa: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions