New Publication from KU Leuven: Understanding the risks of live dengue vaccines

A rare but instructive case: a 57-year-old man developed severe dengue requiring ICU admission just 5 days after receiving TAK-003 vaccination. Kai Dallmeier's team (KU Leuven) comments on what we can learn from this critical incident. 

🔍 The twist: It's not a "vaccine error", but an individual immune problem.  

For instance, some individuals—particularly older men and people with certain autoimmune disorders—may harbor high levels of autoantibodies against interferon-α (AAIAs), a critical component of the body's antiviral defense. Such AAIAs can neutralize antiviral interferon activity, increasing susceptibility to viral infections. As a result, even attenuated viruses used in live vaccines may replicate unchecked, potentially causing disease. 

This mirrors YEL-AVD (yellow fever vaccine-associated viscerotropic disease) — a rare but serious complication affecting people with specific immune defects, not vaccine flaws. 

 The solution: Rather than broad bans based on age or sex, the letter proposes: 

✅ Targeted AAIA screening in high-risk groups before vaccination

 ✅ Personalized risk assessment using biomarkers 

✅ Direct-acting antivirals (DAAs) as rescue therapy if vaccine-associated disease occurs 

The key message: Understanding individual risk factors = safer vaccines for all, not less access. 

This is exactly what Yellow4FLAVI explores: how to use live vaccines intelligently by combining rigorous preclinical research (like our recent Nature Communications Zika results) with personalized medicine strategies. 

Live vaccines are among humanity's most powerful public health tools, providing protection against diseases such as yellow fever and dengue. Notably, the majority of antiviral vaccines—approximately 75%—are based on replication-competent viruses. The challenge isn't to abandon them, but to protect vulnerable individuals while preserving access for the millions who benefit. 

 Letter published in the International Journal of Infectious Diseases (2025) 

Authors: Dallmeier & Alpizar 

🧬 Read the letter here