IVIG REPLACEMENT AFTER
CAR-T: A PRACTICAL GUIDE

Antibodies are proteins made by B cells that recognise and neutralise infections. They are how the body remembers past infections and vaccines, and how it fights off many bacteria and viruses, particularly encapsulated bacteria such as pneumococcus and Haemophilus influenzae. The body normally has five types of antibodies, with IgG being the most abundant and the most clinically important for long-term protection. CD19-directed CAR-T cells attack the CD19 antigen on B cells. Cancerous B cells carry CD19, but so do healthy B cells. When CAR-T succeeds, it usually wipes out both. The body's antibody-producing cells, called plasma cells, may continue to release antibodies for some time, but eventually levels fall, sometimes substantially. This state is called B-cell aplasia, and the resulting low antibody level is called hypogammaglobulinemia. The clinical consequence is increased risk of certain infections, particularly bacterial respiratory infections, sinus infections, and ear infections, and reactivation of certain viruses. Some patients are barely affected; others have repeated infections and need active prevention. IVIG replaces the missing antibodies temporarily, lasting about three to four weeks per dose, and reduces this risk meaningfully when given regularly.

Decisions about when to start IVIG are made by the cell therapy team and follow a few common patterns: Many patients do not need IVIG immediately after CAR-T because residual plasma cells continue producing antibodies for some weeks. The need usually becomes clearer at the three- to six-month follow-up, although some patients need it earlier and others never need it at all.

• Significantly low IgG level on routine post-CAR-T blood test

  Significantly low IgG level on routine post-CAR-T blood testing, particularly below 4 g/L, with thresholds varying between centres

• Recurrent or serious bacterial infections after CAR-T, even

  Recurrent or serious bacterial infections after CAR-T, even if the IgG level is borderline

• Hospitalisation for infection during the first months after

  Hospitalisation for infection during the first months after CAR-T

• Patient factors that raise infection risk, such as prior hea

  Patient factors that raise infection risk, such as prior heavy chemotherapy, transplant history, advanced age, or comorbid lung disease

• Paediatric and adolescent patients, who often have lower thr

  Paediatric and adolescent patients, who often have lower thresholds for starting IVIG given the importance of preventing infections during growth and school years

Source and Manufacturing IVIG is made from pooled blood plasma collected from many healthy blood donors, typically thousands per batch. The plasma is processed to extract and concentrate the antibodies, with multiple safety steps to inactivate viruses and remove unwanted proteins. The final product is mostly IgG and is supplied as a sterile solution for intravenous infusion. Several brand-name products are available globally, with broadly similar clinical effect; selection often depends on local availability and patient tolerance. Typical Dose and Schedule A typical replacement dose is around 0.4 to 0.6 grams per kilogram of body weight, given every three to four weeks. For an adult of 60 kilograms, this works out to roughly 24 to 36 grams per infusion. The exact dose is adjusted based on the IgG level measured before each infusion (called the trough level) and the patient's infection history. Many cell therapy teams aim for a trough IgG of 5 to 7 g/L or higher, although targets vary between centres and individual patients. The Infusion Itself Each infusion is given over two to four hours, depending on the dose, the brand, and the patient's tolerance. The first infusion is usually given more slowly, starting at a low rate that is increased gradually if there are no side effects. Once a stable rate is established, subsequent infusions can run at a similar speed. Pre-medication with paracetamol and an antihistamine is common, especially in the first few infusions, to reduce mild reactions. Subcutaneous Alternative (SCIG) Subcutaneous immunoglobulin (SCIG) is an alternative for some patients. Instead of one large monthly intravenous infusion, smaller doses are given weekly or every other week as a subcutaneous injection, often at home. SCIG suits patients who prefer to avoid hospital visits, who have difficult venous access, or who tolerate IVIG poorly. It produces steadier IgG levels than monthly IVIG. SCIG availability and cost vary by country, and not every patient is a candidate.

Most patients tolerate IVIG well, especially after the first few infusions. Common reactions include: Less common but more important reactions include severe headache (occasionally aseptic meningitis presenting one or two days after infusion), thrombosis or stroke in patients with strong vascular risk factors, kidney injury (rare with modern formulations), haemolysis, and very rare anaphylactic reactions in patients with severe IgA deficiency. The infusion team monitors vital signs throughout and will slow or pause the infusion if reactions occur. Patients should report fever, severe headache that does not respond to paracetamol, vision changes, chest pain, breathlessness, leg swelling, or unusually dark urine to the treating team without delay.

• Mild headache, often during or shortly after the infusion, u

  Mild headache, often during or shortly after the infusion, usually responsive to paracetamol and slowing the infusion rate

• Fatigue or feeling washed-out for a day or two

  Fatigue or feeling washed-out for a day or two

• Low-grade fever or chills

  Low-grade fever or chills

• Muscle aches or joint discomfort

  Muscle aches or joint discomfort

• Mild rash or flushing

  Mild rash or flushing

• Nausea

  Nausea

Regular monitoring helps the team adjust the dose and check for problems. Typical assessments include:

• Trough IgG level before each infusion, or at intervals if do

  Trough IgG level before each infusion, or at intervals if doses are stable

• Complete blood count to check for haemolysis or other haemat

  Complete blood count to check for haemolysis or other haematological effects

• Liver and kidney function tests, especially in older patient

  Liver and kidney function tests, especially in older patients or those with vascular risk

• Review of any infections, hospital admissions, or new medica

  Review of any infections, hospital admissions, or new medications since the last infusion

• Vital signs before, during, and after the infusion

  Vital signs before, during, and after the infusion

• Periodic review of B-cell counts to track recovery; some pat

  Periodic review of B-cell counts to track recovery; some patients see B-cell return after months to years, allowing IVIG to be tapered or stopped

There is no fixed end date. IVIG continues for as long as the patient has clinically significant low antibody levels and infection risk. Many patients need it for at least one to two years after CAR-T, and some need it for longer. The cell therapy and immunology teams typically reassess every six to twelve months by: If recovery looks adequate, the team may extend the interval between infusions, reduce the dose, or pause IVIG to test whether it is still needed. If infections recur or the IgG level drops back, regular replacement is restarted. Some patients can stop permanently; others need indefinite support.

• Measuring B-cell return on flow cytometry

  Measuring B-cell return on flow cytometry

• Watching for the patient's own IgG to recover when IVIG is p

  Watching for the patient's own IgG to recover when IVIG is paused

• Reviewing infection history over the previous year

  Reviewing infection history over the previous year

• Considering whether vaccines (which usually do not work well

  Considering whether vaccines (which usually do not work well in B-cell aplasia) can be re-started

IVIG is one of the more expensive long-term components of CAR-T aftercare, because each infusion uses a substantial dose of donor-derived product. Cost varies significantly by country, brand, and whether the patient is treated in a public hospital, private centre, or at home. In some countries, IVIG for post-CAR-T hypogammaglobulinemia is covered by public health systems or insurance; in others, it is largely out of pocket. Practical planning points for patients returning home from CAR-T treatment abroad:

• Confirm with the local oncology team that IVIG is available

  Confirm with the local oncology team that IVIG is available before discharge

• Identify the closest infusion centre that can deliver multi-

  Identify the closest infusion centre that can deliver multi-hour intravenous infusions safely

• Check whether SCIG is available, since home-based weekly inf

  Check whether SCIG is available, since home-based weekly infusions can be more practical for some families

• Plan for the cost of regular IVIG over at least 12 months, e

  Plan for the cost of regular IVIG over at least 12 months, even if the schedule may change

• Keep a simple infusion log with dates, doses, brand, IgG lev

  Keep a simple infusion log with dates, doses, brand, IgG levels, and any side effects, which is useful for the local team

This comparison is general. The choice between IVIG and SCIG depends on local availability, patient preference, lifestyle, venous access, side effect history, and the recommendation of the treating team.

IVIG is available in most major countries with established cancer and immunology services, although brand availability and reimbursement vary widely. Major Chinese hospitals routinely use IVIG for post-CAR-T patients during the early monitoring window, and patients usually leave with a clear plan for ongoing replacement. In countries such as India, Bangladesh, the Philippines, Vietnam, parts of the Middle East, and CIS regions, IVIG is generally available but patients often need to plan around supply and cost. SCIG is more variably available; it is well established in parts of Europe, North America, and Australia, but less widely accessible in some markets where CancerFax patients live. CancerFax helps patients confirm what is realistic in their home setting before discharge from China, so that the first month back is not the moment when continuity gaps appear.

Frequently Asked Questions

Answers to common questions from patients and families.

This guide is for patient and family education and care navigation support only. It does not replace medical advice, diagnosis, or treatment from a qualified oncologist, haematologist, or immunology team. Decisions about starting, adjusting, dosing, and stopping immunoglobulin replacement must always be made by the treating clinical team, based on the individual patient's full clinical picture. CancerFax does not provide emergency medical care. Patients with severe headache, fever, breathing difficulty, chest pain, sudden weakness, leg swelling, dark urine, or rapidly worsening symptoms during or after IVIG should contact their treating hospital or emergency services immediately.

Structured reference data summarizing key information for this topic.