Immunodeficiency Red Flags: Recurrent Infections and When to Suspect It

When your child keeps getting sick-ear infections, pneumonia, sinus infections-it’s easy to blame it on daycare, cold weather, or bad luck. But what if it’s not luck? What if it’s your immune system failing to fight off even the most common bugs? Recurrent infections aren’t always normal, especially when they’re frequent, severe, or don’t respond to standard treatment. In fact, they might be the earliest and most obvious sign of an underlying immunodeficiency.

How Many Infections Are Too Many?

Most healthy kids get 6 to 12 respiratory infections a year. That’s normal. But if your child has four or more ear infections in 12 months, or two or more pneumonias in a year, that’s a red flag. The same goes for deep skin abscesses, persistent thrush after age one, or infections that require IV antibiotics to clear. These aren’t just annoying-they’re signals your immune system isn’t doing its job.

The American Academy of Allergy, Asthma & Immunology and the European Society for Immunodeficiencies agree: there are clear thresholds. Eight ear infections in a year? That’s not coincidence. Two sinus infections that don’t improve with two months of antibiotics? That’s not just bad timing. These patterns don’t match up with typical childhood illness. They match up with immune failure.

What Makes an Infection a Red Flag?

Not all infections are created equal. Some infections should never happen in a healthy person. If your child gets infections caused by organisms like Candida (fungal thrush) that stick around after age one, or Pneumocystis jirovecii (a fungus that only attacks people with severely weakened immunity), that’s a major alarm. These are called opportunistic infections. They’re the immune system’s last cry for help.

Other red flags include:

• Recurrent deep abscesses in organs like the liver or lungs
• Failure to gain weight or grow normally (failure to thrive)
• Family history of early deaths from infection or known immunodeficiency
• Chronic diarrhea that doesn’t improve
• Absent or very small tonsils and lymph nodes on physical exam

A 2019 study in the Journal of Clinical Immunology found that 78% of children with severe combined immunodeficiency (SCID) had no visible tonsils or lymph nodes. That’s not something you miss if you’re looking for it.

When to Suspect Antibody Deficiency

The most common type of immunodeficiency involves antibodies-specifically, low levels of IgG, IgA, or IgM. These proteins are your body’s missiles against bacteria and viruses. When they’re missing, you get hit again and again.

Common Variable Immunodeficiency (CVID) is the most frequent antibody deficiency in adults. But it can show up in kids too. The diagnostic criteria are strict: IgG levels below 400 mg/dL, plus low IgA or IgM, and a poor response to vaccines. But here’s the catch-many doctors miss it because they look at the wrong numbers.

A pediatrician in Ohio recently shared a case: an 8-year-old with repeated pneumonia. His IgG was 420 mg/dL. That’s above the general cutoff of 400. But for an 8-year-old? That’s abnormally low. Age-adjusted norms show the average is closer to 700 mg/dL. He was misdiagnosed as having chronic bronchitis for over a year.

The Workup: What Tests Actually Matter?

You can’t diagnose immunodeficiency by guesswork. You need specific tests, done in the right order.

Step 1: Complete Blood Count (CBC) with Differential
This checks your white blood cells. In kids over one year, a lymphocyte count under 1,500 cells/μL is suspicious. In infants under one, under 3,000 is a warning sign. Low lymphocytes mean your T cells-your infection fighters-are running low.

Step 2: Immunoglobulin Levels (IgG, IgA, IgM)
These must be interpreted by age. A 3-month-old’s normal IgG is 243 mg/dL. By age 5, it should be 700-1,600 mg/dL. If your child’s IgG is 450 mg/dL at age 6? That’s not normal. It’s low.

Step 3: Lymphocyte Subset Analysis (Flow Cytometry)
This counts your T cells (CD3, CD4, CD8), B cells (CD19), and natural killer cells (CD56). A CD3 count under 1,000 cells/μL in a child over two years is abnormal. This test tells you which part of the immune system is broken.

Step 4: Vaccine Response Testing
This is the gold standard. You give a vaccine-like tetanus or pneumococcal-and then check antibody levels 4 to 8 weeks later. If your child doesn’t make a strong response, they can’t fight off real infections. The CDC says protective tetanus antibody levels must be above 0.1 IU/mL. For pneumococcus, it’s 1.3 μg/mL. If they’re below that, you’ve got a real problem.

Don’t Jump to Immunoglobulin Therapy

Too many patients get IV immunoglobulin (IVIG) without proper testing. A 2020 study in the Annals of Internal Medicine found that 22% of patients started on IVIG didn’t actually have a functional antibody deficiency. They had low IgG, but their bodies could still respond to vaccines. Giving IVIG to these patients doesn’t help-and it’s expensive, invasive, and carries risks.

Before you start lifelong infusions, you must prove the immune system can’t make its own antibodies. That’s why vaccine challenge testing is non-negotiable.

What Else Could It Be?

Not every recurrent infection is immunodeficiency. In fact, up to 43% of cases have other causes.

• Cystic fibrosis: Causes thick mucus that traps bacteria in the lungs. Often mistaken for recurrent pneumonia.
• Structural nasal or sinus problems: Deviated septum, enlarged adenoids-these block drainage and cause chronic sinusitis.
• Inhaled foreign bodies: A child might swallow a peanut, and it gets stuck in the airway. It causes repeated lung infections that look like pneumonia.
• Autoimmune diseases: Lupus or rheumatoid arthritis can lower antibody levels.
• Medications: Steroids, chemotherapy, or even long-term antibiotics can suppress immunity.

That’s why the diagnostic process starts by ruling out these conditions before you even look at the immune system.

What Happens If You Wait?

Delaying diagnosis has real consequences. A 2017 study in the Journal of Allergy and Clinical Immunology showed that children with SCID diagnosed before 3.5 months had a 94% survival rate. Those diagnosed later? Only 69% survived.

The longer you wait, the more damage accumulates. Repeated pneumonia can scar the lungs. Chronic sinus infections can destroy sinuses. Untreated CVID can lead to lung disease, liver disease, or even cancer. Early diagnosis doesn’t just prevent death-it prevents lifelong disability.

What’s Changing Right Now?

In 2023, the FDA approved a new genetic test called StrataID Immune. It checks 484 immune-related genes in one test. It finds the cause in 35% of suspected cases-almost double the old methods. More states now screen newborns for SCID. In 2018, only 26 states did it. Now, 38 do. That’s saving lives before symptoms even appear.

The future is faster diagnosis. Experts predict that within five years, whole exome sequencing will be the first test for suspected immunodeficiency-not the last. AI tools are being trained to predict immune disorders from routine blood tests with 92% accuracy.

But here’s the hard truth: 78% of low- and middle-income countries still can’t test for basic immunoglobulin levels. That’s why awareness matters. If you’re a parent, a teacher, or a doctor, knowing the red flags can mean the difference between a child who grows up healthy-and one who doesn’t.

What Should You Do Next?

If you’re seeing these patterns:

1. Write down every infection: type, frequency, treatment, duration
2. Check growth charts-has your child fallen below the 5th percentile?
3. Look for signs like chronic thrush, abscesses, or absent tonsils
4. Ask about family history: anyone die young from infection? Any cousins with immune problems?
5. Ask your doctor for: CBC, immunoglobulins, lymphocyte subsets, and vaccine response testing

Don’t wait for a specialist to notice. Be the one who asks the question: Could this be an immune problem? You might just save a life.