Can the Boostrix (Tdap) vaccine cause a spike in Thyroid-Stimulating Hormone (TSH) levels, resulting in symptoms like diarrhea and weight loss?

Boostrix Vaccine and TSH Elevation: Relationship to Diarrhea and Weight Loss

Based on the available evidence, the Boostrix vaccine is unlikely to cause a TSH spike within 3 weeks of administration that would result in diarrhea and weight loss. While vaccines can occasionally trigger immune responses affecting thyroid function, this is not a documented side effect of Tdap vaccines like Boostrix.

Documented Side Effects of Boostrix

The Advisory Committee on Immunization Practices (ACIP) and clinical studies have documented the following common side effects of Boostrix:

Local Reactions

• Pain at injection site (most common - reported in 75% of recipients) 1
• Redness and swelling (20-30% of recipients) 1
• Severe pain in 4.6% of recipients 1

Systemic Reactions

• Headache (42-43%) 1
• Fatigue (37%) 1
• Fever >100.4°F (5%) 1
• Gastrointestinal symptoms (26%) 1

Importantly, clinical trials and post-marketing surveillance have not established a link between Boostrix and thyroid dysfunction 1, 2. The gastrointestinal symptoms reported in clinical trials were generally mild and transient.

Thyroid Function and Vaccines

While there is no established connection between Boostrix and thyroid dysfunction, there have been rare case reports of thyroid disorders following other vaccines:

• Some case reports have documented Graves' disease following SARS-CoV-2 vaccination as part of an autoimmune/inflammatory syndrome induced by adjuvants (ASIA) 3, 4
• A study of patients with pre-existing Hashimoto thyroiditis showed some experienced TSH increases after COVID-19 vaccination 5

However, these findings:

1. Were specific to COVID-19 vaccines, not Tdap vaccines
2. Often occurred in patients with pre-existing thyroid conditions
3. Represent rare occurrences rather than expected side effects

Clinical Approach to Your Symptoms

Given your symptoms of diarrhea and weight loss occurring shortly after vaccination:

1. Consider alternative causes: These symptoms are more likely related to other conditions such as:

   • Gastrointestinal infection
   • Inflammatory bowel disease
   • Thyroid dysfunction unrelated to vaccination
   • Other endocrine disorders

2. Appropriate testing:

   • Repeat thyroid function tests to monitor TSH levels
   • Consider testing for thyroid antibodies if not previously done
   • Evaluate for other causes of diarrhea and weight loss

3. Timing consideration: While some vaccine reactions can occur within days of administration, a significant TSH elevation causing symptomatic thyroid dysfunction typically takes longer to develop.

Conclusion

The temporal association between your Boostrix vaccination and symptoms does not necessarily indicate causation. The documented safety profile of Boostrix does not include thyroid dysfunction as a recognized adverse event 1, 2, 6. Your symptoms of diarrhea and weight loss with TSH elevation warrant further medical evaluation to determine their true cause.