Friday, April 28, 2017

Vaccination and Type-1 Diabetes (part 1)

Every now and then I see a posting where someone asks if maybe vaccinations have something to do with causing type-1 diabetes. The following is my collection of data showing that they do not.  It is in two parts because it is too long to be posted on some forums as a single post.

The r-numbers in the text below are references to specific studies later in the text.

Do Vaccinations Cause Type-1 Diabetes or Make It More Common?

In order to answer this question I searched through all the research I could find on humans which was published in peer-reviewed indexed journals, which compared type-1 diabetes rates in vaccinated vs. unvaccinated populations or which compared vaccinated on the standard schedule to vaccinated on a slower schedule.  I do think people with specialized tools might be able to find more research, so if you find any more studies on people, please tell me about them.  I did not include population based studies, as these are much less reliable than studies which directly compare groups.  I must say I was surprised at how much research was out there showing that vaccines did not cause type-1 diabetes.  I had never heard of one such paper, but it turns out there are many.  I view this as reporting bias: papers showing things are safe don't make the news, so the public never hears about them.  I grabbed the first 15 studies I found, and they are listed (with results) below.  

The bottom line is that there are 12 studies which find that vaccines do not increase the rate of type-1 diabetes.  Of these, 2 actually find that vaccines lower the rate of type-1 diabetes, probably by lowering the rates of mumps or rubella in the population [r3, r6].  There are also two review articles [r12, r15], and one meta analysis [r14] which come to the same conclusion: vaccines do not cause type-1 diabetes. Note that one study [r5] claimed that it "supported" the idea that a causal relationship existed.  However the paper's abstract reported that there was no statistically significant difference between type-1 diabetes rates between children who got influenza B immunization and those who did not.   

Now the democratic thing to do is to say 12 studies show vaccines don't cause type-1, 0 show that they do, so the "does not cause" side wins in a landslide.  Or to look at the studies which summarized the findings of all the other studies available when they were written: these were 2 showing vaccines are safe vs. 0 showing they might cause type-1 diabetes.  

Some of the papers looked at the question of timing: did delaying vaccinations result in a lower type-1 diabetes rate?  A total of 3 papers looked at that issue and all of them found that delay did not result in lower rates of type-1 diabetes [r2, r4, r8]. 

One paper [r7] looked at the overall number of vaccines given to one person, to see if that was associated with higher type-1 diabetes rates.  It found no relationship.

Finally, as a separate area of interest: at least 2 of these papers looked at the relationship between breastfeeding or early introduction of cow milk and type-1 diabetes and found no connection [r7,r13].

If you have any doubts about this I urge you to read the quotes from the abstracts below; they are really very strong in showing that vaccines do not cause type-1 diabetes.

Discussion of the Claussen Paper

The Claussen paper [r5] does not show an increased rate of type-1 diabetes after immunization.  Dr. Claussen says that it does, and refers to it that way, but if you look at the actual abstract, you see this:

The difference in cumulative incidence between those receiving 4 doses and those receiving 0 doses is 54 cases of IDDM/100,000 (P = 0.026) at 7 years, (relative risk = 1.26).
And a relative risk of 1.26 is too low to be considered a correlation.  (Most researchers want to see a relative risk of 2, others will accept a relative risk as low as 1.5, but that is rare.  But in any case 1.26 is well below the correlation threshold.  (There is also some discussion of clustering in the abstract, but no numbers are given.)

Results from the Studies and References

Each entry in this list contains a reference number, the title of the paper, the year it was published, a URL where you can see the whole abstract (sometimes the whole paper), and the results and/or conclusions section which you can read.  The indented text is quoted from the study.

[r1] Childhood Vaccination and Type 1 Diabetes (2004)
Results Type 1 diabetes was diagnosed in 681 children during 4,720,517 person-years of follow-up. The rate ratio for type 1 diabetes among children who received at least one dose of vaccine, as compared with unvaccinated children, was 0.91 (95 percent confidence interval, 0.74 to 1.12) for Haemophilus influenzae type b vaccine; 1.02 (95 percent confidence interval, 0.75 to 1.37) for diphtheria, tetanus, and inactivated poliovirus vaccine; 0.96 (95 percent confidence interval, 0.71 to 1.30) for diphtheria, tetanus, acellular pertussis, and inactivated poliovirus vaccine; 1.06 (95 percent confidence interval, 0.80 to 1.40) for whole-cell pertussis vaccine; 1.14 (95 percent confidence interval, 0.90 to 1.45) for measles, mumps, and rubella vaccine; and 1.08 (95 percent confidence interval, 0.74 to 1.57) for oral poliovirus vaccine. The development of type 1 diabetes in genetically predisposed children (defined as those who had siblings with type 1 diabetes) was not significantly associated with vaccination. Furthermore, there was no evidence of any clustering of cases two to four years after vaccination with any vaccine.

Conclusions These results do not support a causal relation between childhood vaccination and type 1 diabetes.
[r2] Childhood Vaccinations, Vaccination Timing, and Risk of Type 1 Diabetes Mellitus (2001)
Conclusions. In this large, population-based, case-control study, we did not find an increased risk of type 1 diabetes associated with any of the routinely recommended childhood vaccines. Our study adds to previous research by providing data on newer vaccines, including hepatitis B, acellular pertussis, and varicella vaccines. For the older vaccines, our results are generally in agreement with previous studies in not finding any increased risks. Ours is the first epidemiologic study to evaluate the possibility that timing of vaccination is related to risk of clinical diabetes in children. Our results on hepatitis B vaccine do not support the hypothesis; risk of type 1 diabetes was not different between infants vaccinated at birth and those who received their first vaccination later in life. The results of our study and the preponderance of epidemiologic evidence do not support an association between any of the recommended childhood vaccines and an increased risk of type 1 diabetes. Suggestions that diabetes risk in humans may be altered by changes in the timing of vaccinations also are unfounded.
[r3] Decline of mumps antibodies in Type 1 (insulin-dependent) diabetic children and a plateau in the rising incidence of Type 1 diabetes after introduction of the mumps-measles-rubella vaccine in Finland (1993)
The results suggest that the elimination of natural mumps by mumps-measles-rubella vaccination may have decreased the risk for Type 1 diabetes in Finland; a possible causal relationship is substantiated by the observed concomitant decrease in mumps antibody levels in diabetic children.
[r4] Association between type 1 diabetes and Haemophilus influenzae type b vaccination: birth cohort study (1999) 
Results: No statistically significant difference was found at any time during the 10 year follow up in the risk of type 1 diabetes between the children born before the vaccination period and those vaccinated at the age of 24 months only (relative risk 1.01). The difference in the risk between the cohort vaccinated first at the age of 3 months and the cohort vaccinated at the age of 24 months only was not statistically significant either (1.06).

Conclusion: It is unlikely that H influenzae type b vaccination or its timing cause type 1 diabetes in children.

[r5] Clustering of cases of insulin dependent diabetes (IDDM) occurring three years after hemophilus influenza B (HiB) immunization support causal relationship between immunization and IDDM.

The difference in cumulative incidence between those receiving 4 doses and those receiving 0 doses is 54 cases of IDDM/100,000 (P = 0.026) at 7 years, (relative risk = 1.26).

This list is continued in part 2.

Joshua Levy
All the views expressed here are those of Joshua Levy, and nothing here is official JDRF or JDCA news, views, policies or opinions.

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