Kesimpta Does Not Significantly Increase Your Risk of Sepsis
Starting Kesimpta (ofatumumab) at age 30 with no history of frequent infections does not put you at high risk for sepsis. The drug primarily increases your risk of common, manageable infections—not life-threatening sepsis.
What the Clinical Data Actually Shows
The FDA label and clinical trials provide clear reassurance 1. In the pivotal ASCLEPIOS I/II trials, serious infections occurred in only 2.5% of Kesimpta-treated patients versus 1.8% with teriflunomide—essentially no meaningful difference 1, 2. The most common infections were:
- Upper respiratory tract infections (39%)
- Urinary tract infections (10%)
These are routine infections that healthy people get, not sepsis or life-threatening conditions.
Long-Term Safety Data Confirms Low Sepsis Risk
Extended follow-up data spanning up to 3.5 years in 1,969 patients showed no opportunistic infections and no cases of progressive multifocal leukoencephalopathy (PML) 3. The serious infection rate remained low throughout this extended period. Real-world Australian data in 170 patients confirmed this: serious infections occurred in only 2.9% of patients 4.
Importantly, there is no documented association between Kesimpta and sepsis specifically in the MS population 3, 2. The FDA label mentions that "serious, including life-threatening or fatal" infections have been observed with anti-CD20 therapies broadly 1, but this language reflects class-wide labeling requirements based on higher-dose IV formulations used in cancer (chronic lymphocytic leukemia), not the MS-specific subcutaneous dosing you would receive.
Why Your Personal Risk Profile Matters
At 30 years old and rarely getting sick, you have protective factors:
- Age: You're not in the high-risk elderly category (≥65 years) that guidelines identify as vulnerable to immunosuppression-related complications 5
- No baseline immunocompromise: You don't have malignancy, aren't on chronic steroids, and don't have malnutrition—all identified high-risk factors for sepsis in immunosuppressed patients 5
- Healthy baseline immune function: Your history of rarely getting sick suggests robust immune defenses
The Immunoglobulin Question
You might worry about Kesimpta lowering your antibody levels. Here's what happens:
- IgM levels decrease but remain above the lower limit of normal in most patients 1, 3
- IgG levels remain stable (4.3% decrease at 48 weeks, then 2.2% increase at 96 weeks) 1
- Critically: Decreased immunoglobulin levels were NOT associated with increased serious infections 3, 2
Recent meta-analysis data shows that while rituximab (a different anti-CD20 antibody) had 11% hypogammaglobulinemia rates, this did not translate to sepsis risk 6. A 2026 real-world study found that baseline immunoglobulin levels and treatment duration—not the choice of anti-CD20 therapy itself—predicted infection risk 7.
What Infections to Actually Watch For
Be vigilant for common infections that need prompt treatment:
- Respiratory infections (colds, bronchitis)
- Urinary tract infections
- Skin infections
These are not sepsis. They're manageable with standard antibiotics when caught early. The FDA label instructs: "Delay KESIMPTA administration in patients with an active infection until the infection is resolved" 1. This is standard precaution, not an indication of sepsis risk.
Critical Caveats
Do not start Kesimpta if you have:
You must be screened for hepatitis B before starting (HBsAg and HBcAb testing minimum) 1. This is because HBV reactivation—though not reported in MS patients on Kesimpta—has occurred with other anti-CD20 therapies and can be fatal 1.
Update your vaccines at least 4 weeks before starting (for live vaccines) or 2 weeks before (for inactivated vaccines) 1. Live vaccines are contraindicated once you start treatment.
Practical Monitoring Approach
Your neurologist should:
- Screen for hepatitis B before initiation 1
- Ensure vaccines are current 1
- Monitor you for infections during treatment (no specific sepsis monitoring needed)
- Consider checking immunoglobulin levels periodically, though this isn't mandated by guidelines 3
The first injection should be given under healthcare supervision to monitor for injection-related reactions (fever, headache, myalgia)—these are not infections and occurred in only 20% of patients, mostly mild 1, 8.
Bottom Line
Your fear of "high risk for sepsis all the time" is not supported by the evidence. Kesimpta increases your risk of common infections that you'll recognize and treat early—not sepsis. The 2.5% serious infection rate is comparable to the general MS population on other therapies 1. At 30 years old with a healthy baseline, you're in a favorable risk category. The dramatic efficacy of Kesimpta (94.5% reduction in relapse rates in real-world data 9) likely outweighs the modest infection risk for most patients with active MS.