What you carry at this position in your DNA and what research says about it.
Hepatitis C Recovery: 9/10 evidence, 71 publications.
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Sample genotype (not yours): C/C
Optimal Viral Clearance and Treatment Response
This genotype is associated with the highest rate of natural recovery from hepatitis C and an excellent response to antiviral medications. It also provides protection against rapid liver disease progression.
What this genotype means: Highest rate of natural viral clearance; Excellent response to hepatitis C therapies; Lower risk of liver scarring and fibrosis progression.
Sample genotype (not yours): C/T
Reduced Viral Clearance and Moderate Treatment Response
This genotype is linked to a lower chance of naturally clearing the hepatitis C virus and a moderate response to standard antiviral therapies. It also carries an intermediate risk of liver scarring.
What this genotype means: Lower likelihood of spontaneous viral clearance; Reduced efficacy of standard antiviral medications; Increased risk of liver fibrosis progression.
Sample genotype (not yours): T/T
Lowest Viral Clearance and Poor Treatment Response
This genotype is associated with the lowest rate of natural viral clearance and a poor response to standard hepatitis C medications. It also correlates with a higher risk of liver disease progression.
What this genotype means: Lowest rate of spontaneous viral clearance; Poor response to standard interferon-based therapies; Higher risk of rapid liver scarring and disease progression.
Gene function and biological role
Gene Function: The IFNL4 gene encodes interferon lambda 4, a type of cytokine protein that plays a critical role in the body's innate immune response against viral infections [1]. This protein is part of the interferon family, which helps signal the immune system to target and destroy invading pathogens [2]. Interestingly, genetic variations that prevent the production of functional interferon lambda 4 are actually beneficial for clearing certain viruses [1] [3]. This gene is highly relevant for predicting how well the immune system can naturally fight off the hepatitis C virus [2] [3]. It also serves as a major genetic predictor of how patients will respond to standard antiviral therapies [1] [2].
Variant Impact: The rs12979860 variant is located in an intron of the IFNL4 gene, where it strongly influences the expression and activity of interferon proteins [1]. The C allele at this position is highly linked to a functional genetic frame that regulates the production of interferon lambda 4 [2]. This molecular change directly alters the liver's inflammatory environment and its ability to clear viral pathogens [1] [4]. As a result, this single nucleotide change is the strongest known genetic predictor of both spontaneous viral clearance and clinical treatment success in hepatitis C patients [1] [2]. It also shows minor associations with other tissue-specific inflammatory conditions [5].
Key Insight: Having a genetic variation that disables a specific immune protein actually makes you much better at naturally clearing the hepatitis C virus.
Location: IFNL4. Chromosome 19 · 19q13.2 · 39.2 Mb
Estimated prevalence by population
Global 39.7%; European 46.9%; African 15.8%; East Asian 86.2%; South Asian 59.8%; Americas 39.1%; Ashkenazi 36.7%; Finnish 57.6%; Middle Eastern 38.3%; Amish 39.8%.
Estimated CC genotype frequency.
Global 43.2%; European 43.2%; African 47.9%; East Asian 13.2%; South Asian 35.1%; Americas 46.8%; Ashkenazi 47.8%; Finnish 36.6%; Middle Eastern 47.2%; Amish 46.6%.
Estimated CT genotype frequency.
Global 17.0%; European 9.9%; African 36.4%; East Asian 0.5%; South Asian 5.1%; Americas 14.0%; Ashkenazi 15.5%; Finnish 5.8%; Middle Eastern 14.5%; Amish 13.6%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Immunity & Inflammation
Infection Susceptibility & Resistance
Hepatitis C Clearance. Evidence: 9/10. Source: PMID 19684573. High Clearance Rate.
Pharmacogenomics
Antimicrobial & Antiviral Response
Antiviral Response. Evidence: 9/10. Source: PMID 19684573. Excellent Response.
Organ Systems
Liver Function & Disease
Liver Fibrosis. Evidence: 4/10. Source: PMID 25740255. Lower Fibrosis Risk.
Endocrine & Reproductive
Female Reproductive Health & Fertility
Ovarian Cysts. Evidence: 6/10. Source: PMID 34594039. Slightly Increased.
Showing effects for C/T genotype
Hepatitis C Clearance. Evidence: 9/10. Source: PMID 19684573. Reduced Clearance.
Antiviral Response. Evidence: 9/10. Source: PMID 19684573. Moderate Response.
Liver Fibrosis. Evidence: 4/10. Source: PMID 25740255. Increased Risk.
Ovarian Cysts. Evidence: 6/10. Source: PMID 34594039. Typical Risk.
Showing effects for T/T genotype
Hepatitis C Clearance. Evidence: 9/10. Source: PMID 19684573. Lowest Clearance Rate.
Antiviral Response. Evidence: 9/10. Source: PMID 19684573. Poor Response.
Liver Fibrosis. Evidence: 4/10. Source: PMID 25740255. Highest Risk.
Ovarian Cysts. Evidence: 6/10. Source: PMID 34594039. Slightly Lower.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Carrying two copies of the protective C allele provides a robust natural defense against persistent viral infections in the liver. Clinical studies show that approximately 80 percent of individuals with this genotype are able to successfully clear the hepatitis C virus when undergoing standard antiviral therapy [1]. Furthermore, this genetic profile is strongly associated with spontaneous viral clearance, meaning the body is far more likely to defeat the virus on its own without medical intervention [2]. In patients who do develop chronic infections, this genotype is linked to a slower rate of liver fibrosis progression, preserving long-term liver health [3]. While it slightly increases the statistical likelihood of developing benign ovarian cysts, the overall health impact is overwhelmingly positive due to superior liver protection [4]. Knowing this status is highly valuable if you ever require liver-related medical care or antiviral treatment.
Highest rate of natural viral clearance; Excellent response to hepatitis C therapies; Lower risk of liver scarring and fibrosis progression.
Sample genotype: CT (Heterozygous)
Carrying one copy of the unfavorable T allele significantly alters the body's natural ability to eliminate certain viral infections. Research indicates that individuals with this intermediate genotype have a reduced rate of spontaneous viral clearance compared to those with the protective CC genotype [1]. When treated with standard antiviral therapies, the likelihood of achieving a sustained viral response drops to approximately 20 to 40 percent [2]. This genetic profile also places individuals at an increased risk for faster progression of liver fibrosis and scarring if a chronic infection is established [3]. On a minor note, this genotype represents a typical baseline risk for developing ovarian cysts [4]. Understanding this genetic status is crucial for healthcare providers when tailoring antiviral treatment protocols and monitoring liver health over time.
Lower likelihood of spontaneous viral clearance; Reduced efficacy of standard antiviral medications; Increased risk of liver fibrosis progression.
Sample genotype: TT (Homozygous)
Carrying two copies of the T allele represents the most challenging genetic profile for natural viral defense and treatment efficacy. Individuals with this genotype have the lowest probability of spontaneously clearing the hepatitis C virus, making chronic infection much more likely [1]. Clinical data show that only about 20 to 25 percent of patients with this profile achieve a successful response to standard interferon-based therapies [2]. There is also an increased likelihood of viral recurrence even after undergoing newer direct-acting antiviral regimens [3]. Furthermore, this genotype is strongly associated with accelerated liver fibrosis and scarring during chronic infections, which demands closer clinical monitoring [4]. Conversely, this profile is associated with a slightly lower risk of developing ovarian cysts [5]. This information is highly relevant for personalizing liver care and selecting optimal modern therapies.
Lowest rate of spontaneous viral clearance; Poor response to standard interferon-based therapies; Higher risk of rapid liver scarring and disease progression.
Variants with shared genetic architecture
rs11881222 · IFNL3 Gene · Chr 19 · Hepatitis C Clearance
rs4803217 · IFNL3 Gene · Chr 19 · Hepatitis C Clearance
rs8099917 · IFNL3 Gene · Chr 19 · Hepatitis C Treatment Response
Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance.
Interferon-λ rs12979860 genotype and liver fibrosis in viral and non-viral chronic liver disease.
A cross-population atlas of genetic associations for 220 human phenotypes.
Content updated August 2026.
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