SIDS and Vaccines: Exploring the Study Stirring Up So Much Debate

A controversial new theory links vaccines to sudden infant death. Here’s why we should take it seriously—but also carefully.

Jun 06, 2025

Sudden Infant Death Syndrome (SIDS) is one of the most tragic and mysterious phenomena in pediatric medicine. Over the last few decades, we've seen a dramatic decline in SIDS rates, largely attributed to public health campaigns like "Back to Sleep" and improvements in infant care. These declines are worth celebrating—and they suggest that vaccines, which have increased in number over the same period, are unlikely to be the primary cause of SIDS. If they were, we’d expect SIDS rates to rise, not fall.

However, declining numbers don’t mean the book is closed. And it certainly doesn’t mean we should stop asking important questions—especially if they pertain to a potential subset of vulnerable infants.

A 2025 study that was just published this week in the International Journal of Medical Sciences adds a compelling new layer to the conversation. I have received several questions on it, so I will try to provide some insight.

The authors explore how variability in the cytochrome P450 (CYP450) enzyme system—critical for metabolizing drugs and chemicals—may influence how infants process vaccine excipients like aluminum, polysorbate 80, and formaldehyde. CYP450 enzyme activity is immature at birth and develops over the first two to three years of life. Add to that the fact that many infants have genetic polymorphisms affecting CYP450 function, and you have a plausible biological mechanism that could help explain rare, idiosyncratic reactions.

The study stops short of claiming a causal link between vaccines and SIDS. Instead, it highlights gaps in our understanding, including underexplored pharmacogenetic factors and limitations in current postmortem investigations. It also points to inflammation-induced suppression of CYP450 enzymes following vaccination, which could hypothetically prolong exposure to immunologic or neurotoxic triggers in certain infants.

🔍 Key Takeaways on Vaccine Timing and SIDS from this article (and this is key because there are many articles out there that would not agree with these findings):

1. Temporal Clustering of SIDS Post-Vaccination:

Data from VAERS (1990–2019) show 75% of SIDS reports occurred within 7 days of vaccination, with a peak on day 2 post-vaccination (Miller 2021).
This non-random distribution suggests a need for further investigation into biological mechanisms, not merely coincidental timing.

2. Immature Liver Enzymes May Prolong Exposure to Vaccine Components:

Infants have reduced CYP450 activity (30–60% of adult levels), particularly CYP2D6 and CYP3A4, which may lead to delayed clearance of vaccine excipients like aluminum, formaldehyde, and polysorbate 80.
Cytokine responses to vaccination can further suppress CYP450 function, potentially compounding metabolic stress.

3. Link Between CYP450, Inflammation, and Respiratory Vulnerability:

Vaccine-induced cytokines may suppress CYP450 activity, prolonging inflammatory states in metabolically vulnerable infants.
In turn, this may interfere with serotonin regulation in the brainstem, a known mechanism implicated in ~70% of SIDS cases.

4. Preterm Infants and Apnea Post-Vaccination:

A randomized trial (Greenberg et al., 2025) found an increased incidence of apnea in preterm infants following routine two-month vaccinations, potentially tied to immune activation and reduced metabolic clearance.

🧬 Proposed Mechanistic Hypothesis:

Vaccination induces cytokine release.
Cytokines transiently suppress CYP450 enzymes.
In infants with immature or genetically impaired CYP450, this leads to prolonged retention of vaccine excipients.
The resulting neuroinflammation or toxic buildup may impact serotonin signaling in the medulla.
This may contribute to fatal cardiorespiratory dysregulation, especially during sleep.

🧪 Implications and Recommendations:

Pharmacogenetic screening (e.g., for CYP2D6/CYP3A5 variants) could help identify high-risk infants.
Postmortem investigations of SIDS should routinely assess CYP450 activity and inflammatory markers.
Calls for research into staggered vaccine schedules, particularly for preterm or metabolically vulnerable infants.
Highlights the need for more nuanced vaccine safety assessments that include metabolic and genetic variables.

While the authors note a temporal association between some vaccines and SIDS cases—especially within the first week post-vaccination—many large-scale studies have failed to confirm such patterns. Temporal clustering does not equal causation. And retrospective database analyses, while useful for hypothesis generation, cannot replace well-controlled, prospective research.

That’s exactly what we need.

As I wrote in Between a Shot and a Hard Place, the science around vaccines should never be off-limits to scrutiny. But we must elevate the standards of inquiry. Prospective, gold-standard trials are essential if we are to understand the role that CYP450 metabolism and immune activation might play in rare adverse events like SIDS. Especially when dealing with a condition as devastating—and still poorly understood—as SIDS, we owe it to parents and the medical community to investigate every credible lead.

The article does not claim causation between vaccination and SIDS but provides a biologically plausible hypothesis that vaccine timing—especially in early infancy—may interact with underdeveloped liver metabolism and immune activation in ways that could contribute to rare but serious adverse outcomes like SIDS. It advocates for more individualized vaccine schedules and research into precision immunization for safer outcomes.

Could a subset of SIDS cases be influenced by metabolic vulnerabilities? It’s possible. Is this worth studying? Absolutely.

Let’s move past binary thinking. Let’s pursue nuance, integrity, and scientific progress. Let’s follow the data—even when it leads us into uncomfortable or uncharted territory.

Because our children deserve nothing less.

Dr. Joel "Gator" Warsh is a board-certified pediatrician based in Los Angeles. He is the author of the best-selling book "Between a Shot and a Hard Place." He writes about children’s health, prevention, vaccine science, and bridging the gap between holistic and conventional medicine.

Citation:
Goldman GS, Cheng RZ. The Immature Infant Liver: Cytochrome P450 Enzymes and their Relevance to Vaccine Safety and SIDS Research. Int J Med Sci. 2025;22(10):2434-2445.

https://www.medsci.org/v22p2434.htm

Between a Shot and Hard Place

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