SIDS: A Parent's Worst Fear Has Nothing to Do With Vaccines

Science Shows Vaccines Don't Cause SIDS — They May Actually Help Prevent It: Your Evidence-Based Guide to Understanding the Research

Every parent knows that heart-stopping moment when they check on their sleeping baby and wait to see the gentle rise and fall of their chest. The fear of Sudden Infant Death Syndrome (SIDS) haunts new parents, making them vulnerable to misinformation that preys on these deeply human anxieties. Recently, a new wave of claims linking vaccines to SIDS has gained traction on social media and alternative health websites, leaving many families confused and worried.

As both a scientist and a parent, I understand the urgency of addressing these concerns. When a recent article from the Health Freedom Defense Fund began circulating in parent groups, my inbox filled with messages from concerned families. While it's natural to question anything that might affect our children's safety, it's crucial to examine these claims through the lens of rigorous scientific evidence.

This article aims to do exactly that - not by dismissing parental concerns, but by carefully examining what decades of research tell us about SIDS, vaccine safety, and infant health. Let's separate fact from fiction, looking at both the history of SIDS research and the latest scientific understanding of this challenging medical issue.

A reminder that I am not an immunologist– so I co-wrote this with Unbiased Science team member, Dr. Aimee Pugh-Bernard– an immunologist extraordinaire, to tackle this from all angles!

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Understanding SIDS: A Complex Medical Challenge

Sudden Infant Death Syndrome remains one of the most challenging issues in infant health. SIDS refers to the unexpected death of an apparently healthy infant under one year of age, with the peak risk occurring between 2-4 months. This timing has led some to question whether vaccinations, which often begin around 2 months of age, might play a role. However, before we start assigning blame, let’s examine the evidence.

The Evidence: What Scientific Research Really Shows

Multiple large-scale studies and comprehensive reviews have consistently found that vaccines do not cause SIDS. Full stop! In fact, some research suggests quite the opposite. A comprehensive meta-analysis concluded that immunizations are associated with a halving of the risk of SIDS. The study states, "Immunisations should be part of the SIDS prevention campaigns. While researchers note this could be partially due to the "healthy vaccine effect," it certainly contradicts claims that vaccines increase the risk of SIDS.

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A large-scale study of over 350,000 infants in California (1993–1998) found no relationship between vaccination and infant deaths, reinforcing the safety of immunization. Similarly, an ecological study analyzing long-term data found no association between diphtheria-tetanus-pertussis (DTP) immunization and SIDS, further confirming that vaccines do not contribute to sudden infant deaths. Similar results emerged from a comprehensive Italian study of 3 million infants conducted between 1999-2004.

Understanding Risk Factors and Prevention

Okay, so then what does increase the risk of SIDS? The scientific community's current understanding of SIDS centers on what's known as the "Triple-Risk Model." This model suggests that SIDS occurs when three factors converge:

1. A critical developmental period in the infant's first year of life

2. An underlying vulnerability that affects the baby's ability to regulate breathing during sleep

3. External stressors such as unsafe sleep positions, excessive bedding, or respiratory infections

This model helps explain why the "Back to Sleep" campaign (now known as "Safe to Sleep") has been so successful, leading to a dramatic 53% reduction in SIDS rates between 1992 and 2001. The rate has continued to decline, reaching 38.4 deaths per 100,000 live births by 2020 compared to 120 deaths per 100,000 live births in 1992.

Addressing the Timing Question

Despite all this, critics often point to the temporal association between vaccination schedules and SIDS cases (they are not convinced that vaccines aren’t a cause because of the timing overlap of vaccine administration and SIDS). However, this correlation is exactly what we would expect given that both vaccinations and SIDS peak during the same developmental window. Any deaths occurring after vaccination are within the range expected by chance - they would have occurred regardless of vaccination status (and we know this because we have studied SIDS rates in vaccinated and unvaccinated children, as described above).

Vaccines are given very early in life because infants are born with a naive immune system. Administering vaccines allows the newborn immune system to start to build immunity and provide long-lasting protection against serious infectious agents, like those for which we have vaccines. Following the recommended immunization schedule is essential for safeguarding the health of newborns and ensuring they have some level of durable immune protection against deadly diseases. Maternal antibodies that crossed the placenta during pregnancy typically provide protection for approximately 6 months. Antibodies are proteins that are degraded over time. Since the source of the antibody (pregnant parent or mom) no longer exists after birth, vaccination is the first step to helping your child build their own immune defenses against harmful pathogens.

Claims Made by the Health Freedom Defense Fund

A recent article from the Health Freedom Defense Fund (HFDF) has been widely shared, alleging a link between vaccines and Sudden Infant Death Syndrome (SIDS) which has put this topic back in the spotlight. The article makes several misleading claims, including:

1. Vaccines are a cause of SIDS. HFDF cites studies that rely on small sample sizes, flawed methodologies, and unverified adverse event reports to claim a causal link between vaccines and infant deaths. However, review of the scientific literature reveals the opposite - that vaccines may actually be protective. While the exact immune-mediated mechanisms behind this benefit have not been fully elucidated, it may be due to decreased respiratory infections, which are implicated in the ‘Triple Risk’ model of SIDS.

2. Preterm infants are at greater risk of severe adverse reactions to vaccines. The article references studies suggesting that preterm infants experience life-threatening apnea and bradycardia after vaccination, implying that vaccines are unsafe for this population.

3. VAERS data is proof of vaccine-related deaths. The article misuses data from the Vaccine Adverse Event Reporting System (VAERS) to suggest that vaccines are responsible for a significant number of infant deaths, failing to acknowledge that VAERS reports are unverified and cannot establish causation.

4. Multiple vaccines given at once are dangerous. The article argues that receiving multiple vaccines in one visit overwhelms an infant’s immune system and increases the risk of adverse outcomes. This is simply not true. The immune system is built to handle trillions (yes, trillions!) of different pathogens. Why? The immune system is made up of trillions of individual immune cells - called B cells and T cells - that each have unique specificity, which means that each cell was built to defend the body from a different target or pathogen. While one cell may combat the chickenpox virus (aka varicella zoster virus) another cell may fight off the flu virus. The combination of every B and T cell in the immune system allows us to fight off any pathogen that comes our way. There is individual specificity (when looking at one immune cell) and combined diversity (when lumping them all together). The beauty of the immune system is that when a particular pathogen enters our body - like a harmless form in a vaccine - only the handful of immune cells that are specific for that pathogen will respond. The rest remain at ease waiting for their target to enter the body. The saying “too many too soon” is simply untrue based on the fact that the immune system is composed of trillions of cellular specialists who only engage when their target has entered the body. Further, the number of antigens or small bits of pathogen in all vaccines on the childhood immunization schedule is much less (~320) compared to the number of antigens encountered out in the world as we breathe, touch and eat through our daily existence. There is no way to overwhelm the immune system. Period.

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   Combination vaccines are administered to reduce the number of needle pokes children receive at doctor's visits while increasing protection against a combination of two or more pathogens. Combination vaccines have been rigorously tested to be safe and effective, cut down on office visits, and reduce the overall number of injections children need to receive. They're a win-win: less stress for kids and more efficient protection against multiple diseases.

5. The U.S. infant mortality rate is high because of its aggressive vaccine schedule. HFDF cites misleading analyses claiming that the U.S., despite having one of the most comprehensive vaccine schedules, has worse infant mortality outcomes than other high-income nations due to over-vaccination. This is a classic example of correlation being confused with causation. The U.S.'s higher infant mortality rate is well-documented to stem from systemic healthcare inequities, lack of universal access to prenatal care, higher rates of preterm births, and significant racial and socioeconomic disparities in healthcare access and quality – not from its vaccination schedule. In fact, countries with similar or more comprehensive vaccination schedules, such as Japan and Sweden, have some of the lowest infant mortality rates in the world, definitively disproving this claim.

Correcting Specific Points Made by Health Freedom Defense Fund

This article covers a lot of ground and cites several articles, all of which have critical issues.

Issues with the article:

1. Claims vaccines are connected to SIDS when we know this is not the case

2. Relies heavily on Neil Z. Miller, who has no scientific or medical qualifications and has a strong history of spreading falsehoods about vaccines

   1. A publication in the Journal of American Physicians and Surgeons (a journal that has published articles denying HIV causes AIDS and that vaccines cause autism, among other falsehoods) by Miller claims that combining childhood vaccines at one visit isn’t safe, but this isn’t true. It misuses VAERS data to show a causal relationship when the database isn’t capable of proving such relationships due to the unverified nature of its reports

   2. Another publication by Miller in 2011 says that SIDS is caused by vaccination– but is faulty and relies on a spurious correlation, as well as poor methods for assessing the question at hand. While some studies have observed transient apnea (brief pauses in breathing) in preterm infants following immunization, these events are short-lived and not linked to long-term health complications or increased SIDS risk. The American Academy of Pediatrics (AAP) and the CDC strongly recommend that preterm infants receive vaccinations on schedule based on their chronological age, as they are at greater risk of severe complications from vaccine-preventable diseases.

      1. Yet another publication by Miller in 2023, arguing the same point, has similar issues

      2. An example of how poor their methodology is: they count 1 dose of a multivalent vaccine, which protects against multiple diseases, as multiple vaccine doses, which is not true.

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Reviewing the Studies Cited by the Health Freedom Defense Fund

While this newsletter addresses many overarching issues related to vaccinations and SIDS, we also want to briefly comment on specific studies cited by the Health Freedom Defense Fund (HFDF) to demonstrate that we have thoroughly reviewed their sources. Below, we provide a breakdown of these studies and explain why they do not support the conclusion that vaccines cause SIDS.

1. "Apnea After 2-Month Vaccination in Hospitalized Preterm Infants" (JAMA Pediatrics, January 6, 2025):

This study observed that hospitalized preterm infants exhibited higher rates of apnea within 48 hours post-vaccination compared to unvaccinated counterparts. While the findings indicate a temporal association between vaccination and apnea episodes, they do not establish a causal link to SIDS. Apnea in preterm infants is a known condition, and transient increases post-vaccination have been documented without leading to long-term adverse outcomes or increased SIDS risk. The study found a lack of serious adverse events and concluded that current immunization recommendations should remain in place for hospitalized preterm infants.

2. "Apnea after immunization of preterm infants" (1997):

This research reported that 12% of 97 preterm infants (or 11 infants) experienced recurrent apnea within 72 hours post-immunization. However, the study's small sample size limits the generalizability of its findings. Moreover, while it highlights a temporal association, it does not provide evidence of a causal relationship between vaccinations and SIDS.

3. "Interleukin-6, C-reactive protein, and abnormal cardiorespiratory responses to immunization in premature infants" (1998):

The study found elevated levels of inflammatory markers (IL-6 and CRP) in preterm infants following immunization. However, elevations in these markers are a normal immune response to vaccination and are not indicative of harm. The immune system normally responds to pathogens through inflammation and the release of proteins called interleukins (IL) that coordinate and regulate the immune response. CRP is a marker of inflammation and simply indicates that the immune system is doing its job and initiating a protective response. The study did not establish a connection between these immune responses and an increased risk of SIDS.

4. "Relative trends in hospitalizations and mortality among infants by the number of vaccine doses and age, based on the Vaccine Adverse Event Reporting System (VAERS), 1990-2010" (2012):

This study suggested that infants receiving multiple vaccines had higher hospitalization and mortality rates. However, VAERS is a passive surveillance system that collects unverified data, making it unsuitable for establishing causation. The study's reliance on VAERS data without confirmation of vaccine-related adverse events limits its validity.

5. "Infant mortality rates regressed against number of vaccine doses routinely given: Is there a biochemical or synergistic toxicity?" (2011):

This ecological study claimed a correlation between the number of vaccine doses and infant mortality rates across nations. However, correlation does not equal causation. Ecological studies are prone to the ecological fallacy, where associations observed at the population level do not necessarily hold at the individual level. The study also failed to account for confounding factors such as healthcare quality, socioeconomic status, and reporting practices, which all influence infant mortality rates.

6. "Vaccines and sudden infant death: An analysis of the VAERS database 1990–2019 and review of the medical literature" (2021):

This analysis reported that a significant proportion of infant deaths occurred within seven days post-vaccination. However, as previously noted, VAERS data are unverified and cannot establish causation. The study’s methodology did not account for the background rate of infant mortality or potential reporting biases, making its conclusions unreliable.

The Role of Safety Monitoring

The Vaccine Adverse Event Reporting System (VAERS) is sometimes cited as evidence of vaccine-related deaths. However, it's crucial to understand that VAERS is a passive reporting system that collects any adverse event following vaccination, regardless of whether a causal relationship exists. It's important to note that VAERS data cannot establish causation; it is primarily used to detect potential safety signals that require further investigation. The CDC has repeatedly stated that VAERS reports alone do not confirm a link between vaccines and adverse events, as reports are unverified and can be submitted by anyone. Instead, public health agencies use more rigorous surveillance systems, such as the Vaccine Safety Datalink (VSD) and the Clinical Immunization Safety Assessment (CISA) Project, which rely on validated medical records to assess vaccine safety. It serves as an early warning system but cannot establish causation.

Sidenote: we have talked about VAERS til we’re blue in the face! You can read a deep dive here:

Real Disparities That Need Attention

While focusing on disproven vaccine-SIDS links, we risk overlooking real disparities in SIDS rates that demand attention. Current data from the CDC shows that American Indian/Alaska Native, Black, and Native Hawaiian/Pacific Islander infants experience SIDS rates approximately 2.8 to 2.9 times higher than White infants. These disparities reflect systemic healthcare inequities that require urgent attention and targeted interventions. As discussed previously, extensive research has shown that these disparities are not linked to vaccination rates but rather to factors such as healthcare access, socioeconomic conditions, and safe sleep practices. For example, lower rates of safe sleep adherence, increased exposure to secondhand smoke, and delayed access to prenatal care are all contributing factors to the elevated SIDS risk in some communities. Addressing these disparities requires targeted education and public health policies that ensure all families receive proper guidance on SIDS prevention.

Moving Forward: Focus on Prevention

By focusing on evidence-based prevention strategies and ensuring timely immunizations, we can continue to reduce the incidence of SIDS and protect infant health. It's imperative to rely on rigorous scientific research and public health recommendations to guide our actions in safeguarding our children's well-being.

• Placing babies on their backs to sleep

• Using a firm sleep surface

• Keeping the sleeping area clear of soft objects and loose bedding

• Maintaining appropriate room temperature

• Avoiding exposure to smoke, alcohol, and illicit drugs

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  Final thoughts…

The journey to understanding and preventing SIDS has been one of medicine's most important success stories, even as it remains one of its most heart-wrenching challenges. Through decades of careful research, we've discovered ways to dramatically reduce SIDS risk - from the Back to Sleep campaign to improved prenatal care. These evidence-based interventions have saved thousands of lives.

Yet our work isn't done. The persistent racial disparities in SIDS rates demand urgent attention and action. Rather than being distracted by debunked theories about vaccines, we need to focus our energy on addressing these real inequities and ensuring every family has access to quality healthcare and SIDS prevention education.

For parents reading this article, know that you're not alone in your concerns about your baby's safety. The best way to protect your child is to follow evidence-based safety guidelines while ensuring they receive the full benefits of modern preventive medicine, including vaccines. Remember: pediatricians, nurses, and public health professionals worldwide share your goal - healthy, thriving babies who grow into healthy, thriving children.

If you're concerned about your baby's health or sleep safety, don't hesitate to reach out to your healthcare provider. They can provide personalized guidance based on your specific situation and the latest medical evidence. Together, we can continue making progress in preventing SIDS while protecting infants from vaccine-preventable diseases.

For more detailed information on the relationship between vaccines and SIDS, the Children's Hospital of Philadelphia provides a comprehensive overview that addresses common concerns and summarizes current research findings.

Stay curious,

Unbiased Science

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