Understanding SARS-CoV-2 IgG: Normal vs Optimal Ranges

?What is SARS-CoV-2 IgG?

SARS-CoV-2 quantitative IgG antibodies measure the level of IgG antibodies against SARS-CoV-2 spike protein (or nucleocapsid, depending on assay) developed after COVID-19 infection or vaccination. Quantitative assays (in AU/mL or BAU/mL) allow tracking of antibody levels over time and across vaccination doses. IgG antibodies typically peak 2–4 weeks after infection or vaccination and wane over months.

!Why It Matters

Quantitative SARS-CoV-2 IgG helps assess immune protection status, guide booster vaccination timing, evaluate vaccine response in immunocompromised individuals, and screen for prior COVID-19 infection in serosurveillance. Studies correlate higher spike IgG levels (particularly neutralising antibodies) with greater protection against severe disease and hospitalisation. Hybrid immunity (infection + vaccination) produces the highest and most durable antibody levels.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• No direct symptoms — this is an immune status marker
• Low IgG after vaccination may indicate suboptimal vaccine response
• May be ordered to document prior COVID-19 exposure for long COVID workup
• Waning IgG below protective threshold may indicate need for booster

How to Improve Your Levels

• 1COVID-19 vaccination: primary series and boosters are the most effective way to raise protective IgG
• 2Optimise vaccine response: ensure adequate vitamin D, zinc, and avoid immunosuppressants peri-vaccination
• 3Immunocompromised individuals may require additional vaccine doses or monoclonal antibodies
• 4Natural infection with vaccination (hybrid immunity) produces highest antibody levels

When to Test

Post-vaccination immune assessment; immunocompromised patients checking vaccine response; long COVID evaluation; serosurveillance; uncertain vaccination status documentation.

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