The more aluminum a child was exposed to via vaccination by the age of 2, the more likely they were to have developed asthma by the age of 5, according to a study published in September in Academic Pediatrics. The research highlighted a potential issue that needs further study, according to experts, but it comes with caveats, and alone it cannot prove that aluminum causes asthma or suggest that physicians should stop or delay vaccines for children.
The prevalence of asthma in the United States has increased only slightly in the past two decades. In 2019, 7.8% of adults had asthma compared to 7.4% in 2001. The rates of both childhood and adult asthma vary widely from state to state.
The researchers split the kids into two groups: those with and without eczema, because the two diseases are related. In the study, 2.1% of kids who did not have eczema developed asthma by age 5, and 6% of those with eczema did.
Aluminum is a vaccine adjuvant. That means it is added to vaccines to help your immune system mount a more robust response. It’s not in COVID-19, influenza, or MMR (measles, mumps, rubella) shots, but it is in many others such as hepatitis B and pneumococcal. Previous studies found the risks of aluminum exposure—from both vaccines and diet—to be extremely low to infants.
The September 2022 study was a retrospective analysis, meaning that scientists reviewed children’s medical records in hopes of gleaning insights into their health. They did not randomize children into groups that did or did not receive certain vaccines, as it would be highly unethical to randomly deny children protection from illnesses. The researchers estimated the amount of aluminum the children were exposed to based on which vaccines they had received. The variability came from some patients receiving all recommended vaccines and others missing some doses.
While the retrospective study allowed for a large number of children (nearly 327,000) to be studied, it also means that researchers cannot determine cause and effect, because they were unable to control the variables. Children who receive fewer vaccines may be very different from children who received more by the age of 2 and may grow up in very different environments.
The researchers took care to analyze the data several different ways, to see if another variable, such as not having been breastfed could explain the increase in asthma, but none did.
Still, there was some important data the team didn’t have, such as whether the children had family histories of asthma or lived in homes where they were exposed to secondhand smoke, both of which could raise their overall risk of asthma.
MedShadow reached out to Daniel Salmon, PhD, a professor of international health in the Johns Hopkins University Bloomberg School of Public Health, who studies vaccine safety and risk communication to explain what the researchers did, and what the study means for you and your family.
MedShadow: Can you walk me through what the researchers actually did in this study?
Dr. Salmon: They looked at children born between 2008 and 2014 and followed them until 2017. It was a retrospective study, so looking at children’s health history backwards. Then they looked at the level of aluminum exposure from vaccines. And, they looked at whether they had persistent asthma or not, and what they found was, as the aluminum exposure increased, the risk of asthma increased.
MedShadow: Were you surprised at all by those results?
Dr. Salmon: I’m not surprised it was looked at, but I am surprised that there was what looks like an association. They did a lot of sub-analyses. They did seven sub-analyses where they did things like getting rid of the kids that had less than one or more than five grams [of aluminum in their vaccines]. These are the outliers. For example, kids who had zero doses, they often got no vaccines, and are very different [from kids who did get vaccines]. And when they did that, the relationship still stood.
And they did seven sub analyses to see, “if we do this, does it explain the data?” And the answer with all seven was it doesn’t really show that there’s a problem with the data.
MedShadow: What makes researching questions like “does exposure to aluminum in vaccines raise a child’s risk of asthma?” difficult to study and answer?
Dr. Salmon: It’s hard for a lot of reasons. It’s hard because you’re using observational data. And that’s really imperfect. It’s not randomized, so that makes causal inference much more difficult. If you had a randomized controlled trial with these findings, you would give it a lot more weight.
Here, you’re worried about confounding and bias associated with who got the vaccine, who didn’t get the vaccine, and whether or not they were diagnosed with asthma.
Additionally, this is a sensitive topic. And I don’t want to scare people. The bigger issue is how do you do this science in a way that is rigorous, objective, timely, and reasonably transparent, and not scare people.
MedShadow: What kind of study needs to be done for you to say, “okay, we need to get aluminum out of vaccines or kids shouldn’t have these shots?”
Dr. Salmon: Well, it’s a really complicated issue, and it’s not just about one study. Doing a global study, we would have a lot more variability in how much aluminum people get from vaccines, because there’ll be a lot of variability in the vaccines that are used in different countries. So that’ll help a lot. There’s not much variability in this study. We’ll also get much bigger numbers.
I hope that that happens quickly. It will still take a year to have results and to really do it carefully in a lot of countries. And then, we can do genomic studies, as well.
So if there’s an issue [such as a rise in asthma cases], we can see if it’s genetically based, because, why is it some kids would respond one way and not others? We will also need to measure things like attending daycare, secondhand smoke, and make sure that they’re not the explanation.
But even if we came out and found the same thing with all these different, improved approaches, you still have to be careful drawing definitive causal conclusions.
MedShadow: What should parents take away from this study?
Dr. Salmon: Even if you showed that aluminum was an issue, then you get into risks versus benefits. And, you have to look at the benefits of the vaccines and make that comparison. You can’t just take aluminum out. You’d have to replace it with a different adjuvant. And we’d want to make sure that adjuvant didn’t cause a similar problem.
This commentary says aluminum exposure from vaccines is roughly doubling the rate of asthma. And that’s actually a hard calculation to do. But if that were the case, you’d have to compare your risk of asthma to your risk of pertussis, measles, pneumococcal, or hepatitis B. We know that these vaccines protect your child against a lot of terrible diseases. There’s no question there. The evidence is overwhelming.
We also know what’s going to happen if we stop vaccinating. For example, there were controversies around the whole cell Pertussis vaccine. Sweden stopped using the vaccine altogether, and pertussis came back, and the case fatality rate was just about as high as it was before there was a vaccine. So, what I would say to a parent is, “this study does show that people are looking and we need to look more.”