Vaccines, Asthma, & Allergies: Separating Fact from Fear

What decades of research tell us about vaccination safety

Vaccines and the Risk of Asthma and Allergies: A Deeper Dive

If your child or a loved one has been diagnosed with asthma, you probably hit the internet looking for answers. You likely stumbled upon claims about potential links between vaccines and the development of asthma or allergies. This newsletter aims to provide a comprehensive analysis of this complex issue, delving into the scientific evidence and addressing common questions.

We're fortunate to have immunologist Dr. Aimee Pugh Bernard on the Unbiased Science team to guide us through the evidence.

Key Takeaways (discussed in detail below):

1. The scientific evidence on vaccines and allergic conditions is extensive and nuanced. While some studies show potential associations, the majority of large-scale research indicates either no increased risk or possible protective effects.

2. Multiple large epidemiological studies, including one with 326,991 children, have found that the benefits of vaccines substantially outweigh any potential risks. Even when statistical associations are found, the effect sizes are typically small with questionable real-world significance.

3. Aluminum in vaccines has been rigorously studied and deemed safe. The amount received through vaccines (4.4 mg in first 6 months) is significantly less than typical dietary exposure from breast milk (7 mg), formula (38 mg), or soy formula (117 mg).

4. Certain vaccines, like BCG and DTP, may actually help protect against allergic diseases in some populations, challenging the notion that vaccines increase allergy risk.

5. Recent advances in vaccine safety research have led to important clinical changes - for example, the CDC no longer recommends special precautions for people with egg allergies receiving flu vaccines.

6. While research continues, the scientific consensus is clear: vaccines remain one of our most effective tools for preventing serious diseases, with decades of safety data supporting their use.

   Let’s discuss…

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The Hygiene Hypothesis and Early Concerns

The "hygiene hypothesis" proposes that early exposure to germs and infections is crucial for training the immune system to differentiate between harmless substances (like pollen) and actual threats (like viruses). Some worry that vaccines, by preventing certain illnesses, might disrupt this process and increase the risk of allergies or asthma. Yet, knowing that vaccines allow our immune system to train against harmless versions of the pathogen should help decrease this concern.

In examining potential concerns about vaccine safety, it's important to understand that aluminum from vaccines makes up a small portion of an infant's total aluminum exposure. Pharmacological studies show that during the first six months of life, infants receive about 4.4 milligrams of aluminum from vaccines, while they receive more through diet: breast-fed infants ingest about 7 milligrams, formula-fed infants about 38 milligrams, and infants fed soy formula nearly 117 milligrams during the same period.

Large-Scale Studies: What the Data Shows

The relationship between vaccines and asthma or allergies is multifaceted and, like all realms of science, not fully elucidated and evolving as more evidence accumulates. Some studies suggest potential associations, while most others indicate no increased risk or even protective effects.

A comprehensive observational study of 326,991 children conducted through the Vaccine Safety Datalink in 2023 examined the relationship between aluminum exposure from vaccines before 24 months of age and the incidence of asthma between 24-59 months (2-5 years of age). The study found a statistical association between vaccine-associated aluminum exposure and asthma risk (adjusted hazard ratio 1.26 for children with eczema and 1.19 for children without eczema). However, the researchers emphasized that these findings do not constitute strong evidence for questioning aluminum safety in vaccines. The authors noted several important limitations: the effect size was small, meaning the observed difference between groups was minimal with questionable practical real-world significance; there was a possibility of residual confounding, suggesting additional unmeasured factors may have influenced the results; and they were unable to account for other environmental exposures and dietary sources of aluminum. The authors recommended further research to better understand these relationships.

Mixed Findings? Studies Showing Potential Links

• Inactivated Vaccines and Allergies: A study from Japan found that children who received multiple inactivated vaccines before six months of age showed a higher prevalence of asthma, wheezing, and eczema at 12 months. This suggests a possible link between cumulative vaccine exposure and allergic symptoms, although the results should be interpreted cautiously. However, it is important to note that this study had limitations, including reliance on parental reports for allergy diagnoses and lack of consideration for other factors like family history and environmental exposures.

• Influenza Vaccine and Asthma: An increase in airway obstruction was observed in asthmatic patients after receiving an influenza vaccine, suggesting a potential endotoxin-like effect rather than an allergic reaction. However, this study was small and did not assess long-term effects.

Protective Effects: When Vaccines May Reduce Allergy Risk

• BCG Vaccine: The Bacillus Calmette-Guerin (BCG) vaccine for tuberculosis, given at birth, was associated with a reduced risk of allergic diseases in some populations, supporting the idea that exposure to certain infectious agents might modulate allergy development.

  DTP Vaccine: In animal models, the diphtheria-tetanus-pertussis (DTP) vaccine reduced specific IgE levels, the immunoglobulin associated with allergies, and inflammation related to respiratory allergies. These findings suggest a potential protective effect against allergies.

  General Vaccine Safety: Most epidemiological studies do not find a significant increased risk of asthma or allergies due to vaccines. Some studies even suggest a weak protective effect, although this is not consistently observed across all research. A comprehensive review of epidemiological studies examining vaccinations like diphtheria, tetanus, pertussis, and BCG found no increase in the risk of developing allergic disease. These findings, combined with decades of vaccine safety monitoring, provide strong evidence that current aluminum-containing vaccines have a favorable safety profile.

Managing Rare Allergic Reactions to Vaccines

• COVID-19 Vaccines: Allergic reactions, including anaphylaxis, have been reported following COVID-19 vaccinations, particularly in individuals with a history of allergies or asthma. However, these reactions are rare and typically manageable. Further, most people who had an immediate reaction after a COVID-19 vaccine received a subsequent dose at a later date without problems.

• Influenza Vaccines: Concerns about allergic reactions after the influenza vaccine have significantly decreased in recent years based on extensive studies showing that severe allergic reactions to flu vaccines in people with egg allergy are incredibly rare. Starting with the 2023-2024 flu season, the CDC no longer recommended additional safety concerns for people with egg allergy.

Addressing the Aluminum Concern

Concerns have been raised about the aluminum in vaccines potentially contributing to the development of asthma or allergies. However, the amount of aluminum in vaccines is very small and considered safe. Aluminum is a naturally occurring element found in certain foods, water, and even breast milk. The aluminum in vaccines is used as an adjuvant, which helps to boost the immune response and make the vaccine more effective.

A common question surrounds the difference in health risk between ingesting or eating aluminum in food and the aluminum adjuvant that is injected through vaccination. It’s true that the amount of aluminum received through a vaccine on any given day may be relatively higher than what is found in food ingested that same day. Over time, we are exposed to more aluminum through the food we eat compared to the low level of aluminum in the vaccine schedule endorsed by the American Academy of Pediatrics. For reference, the amount of aluminum in vaccines during the first 6 months of life - if following the recommended immunization schedule - is similar to the amount found in 1 liter of infant formula.

The key point is that the amount of aluminum in vaccines has been rigorously tested and deemed safe.

Research has shown that aluminum in the body follows predictable patterns: in blood plasma, 90% of aluminum disseminates by binding to a transport protein (transferrin) and 8% as part of the aluminum-citrate complex. Studies of aluminum distribution have been precisely quantified using specialized isotope tracking, allowing researchers to understand exactly how the body processes this element. This research has shown that brain penetration of aluminum under physiological conditions ranges from 0.001% to 0.005% per gram of brain tissue, regardless of the route of administration.

As an example, one large study looked at whether childhood vaccinations (like diphtheria, pertussis, tetanus, polio, and smallpox) are associated with asthma and allergic diseases in people aged 7 to 44. No connection between these vaccinations and the risk of developing asthma or allergic conditions was found. Another study reviewed epidemiologic studies with data from diphtheria, tetanus, pertussis, measles, mumps, rubella and BCG vaccinations in infancy and found no increase in the risk of developing allergic disease. Combined, these and other several large studies have not found a link between aluminum adjuvants and the development of asthma or allergies.

The Bottom Line: Why Vaccines Remain Essential

Despite the complexities surrounding the relationship between vaccines and asthma or allergies, the scientific consensus remains clear: the benefits of vaccination in preventing serious diseases far outweigh the potential risks. Vaccines have been instrumental in dramatically reducing the incidence of numerous infectious diseases, saving countless lives, and preventing disability. PS: Check out Immunize.org - a stable source of credible vaccine info. And yes, we know we have said all this a million times…but it bears repeating!

Looking Ahead: Future Research Directions

While the current evidence does not support a significant causal link between vaccines and asthma or allergies, continued research is essential to fully understand these complex relationships. Ongoing studies will help to refine our understanding of the potential risks and benefits of vaccines, allowing for the development of even safer and more effective vaccination strategies.

Making Evidence-Based Decisions

The science is clear - while researchers continue to study the nuanced relationships between vaccines and allergic conditions, decades of data support the safety and critical importance of vaccination. Understanding both the evidence for safety and the limitations of studies suggesting potential risks allows families to make confident, informed decisions about vaccination. The dramatic reduction in infectious diseases, coupled with the favorable safety profile of modern vaccines, demonstrates why they remain a cornerstone of public health and child wellbeing.

Stay Curious,

Unbiased Science

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