TdVax Side Effects: What to Expect and When to Call Your Doctor

TdVax, the tetanus and diphtheria (Td) vaccine made by MassBiologics, was permanently discontinued in 2024. However, millions of people received TdVax doses prior to its discontinuation, and its current-day equivalents — Tenivac, Adacel, and Boostrix — share a nearly identical side effect profile. Whether you received TdVax in the past or are preparing to receive a Td/Tdap vaccine now, understanding what to expect is important.

Common Side Effects: What's Normal?

Most people experience mild to moderate side effects after a Td or Tdap vaccine. These typically appear within 12–24 hours of the injection and resolve within 1–3 days. Common reactions include:

• Injection site reactions: Pain, soreness, swelling, redness, warmth, and induration (hardening) at the injection site are the most common reactions. This is the immune system's normal response to the vaccine antigen.
• Headache: Mild to moderate headaches are commonly reported, typically resolving within a day or two.
• Muscle weakness or aches: General muscle soreness or weakness, often described as similar to post-workout soreness, is common in the arm that received the injection.
• Joint pain: Some patients experience mild joint discomfort, particularly in the shoulder of the injection arm.
• Fatigue and malaise: Feeling tired or "off" for 1–2 days after vaccination is common and reflects a normal immune response.
• Low-grade fever: A mild fever (typically under 101°F/38.3°C) may occur, especially in younger patients.

These side effects are signs that the vaccine is working — your immune system is producing antibodies in response to the tetanus and diphtheria toxoids. They are not reasons to avoid getting vaccinated.

Why Does My Arm Hurt So Much After a Tetanus Shot?

Arm soreness is one of the most commonly reported reactions after any tetanus-containing vaccine. This is largely caused by the aluminum adjuvant in the vaccine (used in TdVax, Tenivac, Adacel, and Boostrix alike), which enhances the immune response but also causes local irritation. People who receive booster doses more frequently than recommended may experience more pronounced injection site reactions because of already-elevated antibody levels.

To manage injection site discomfort: apply a cold pack (wrapped in cloth, not directly on skin) to the injection site in the first 24 hours; gently exercise the arm; and take an over-the-counter pain reliever like acetaminophen or ibuprofen if appropriate for you.

Serious Side Effects: When to Call Your Doctor Immediately

Serious reactions to Td vaccines are rare, but they do occur. Seek emergency medical care or call 911 if you experience any of the following:

• Signs of anaphylaxis (severe allergic reaction): Hives, widespread rash, difficulty breathing, swelling of the face or throat, dizziness, rapid heartbeat, or collapse within minutes to an hour of receiving the vaccine. This is a medical emergency — call 911.
• Severe pain or inability to move the shoulder: This may be SIRVA (Shoulder Injury Related to Vaccine Administration), caused by the vaccine being accidentally injected into the bursa or rotator cuff rather than the deltoid muscle. SIRVA can cause prolonged shoulder pain and limited range of motion.
• Arthus-type reaction: Severe local swelling, pain, and bruising extending beyond the injection site, usually occurring in people with very high pre-existing antibody levels from prior frequent vaccination. If this occurs, discuss with your provider — you may not need another tetanus booster for 10 years.
• Guillain-Barré Syndrome (GBS): An extremely rare but serious neurological condition. Symptoms include muscle weakness starting in the legs, difficulty walking, and in severe cases, paralysis. The Institute of Medicine has identified a possible causal relationship between tetanus toxoid vaccines and GBS. If you develop progressive muscle weakness in the days to weeks after vaccination, seek immediate medical attention.
• Brachial neuritis (Parsonage-Turner Syndrome): Sudden severe shoulder and arm pain followed by muscle weakness in the affected arm, typically beginning days to weeks after vaccination. This rare complication should be evaluated by a neurologist.

What About Fainting After a Tetanus Shot?

Syncope (fainting) is a known post-vaccination reaction — not specific to Td vaccines, but common enough after any injection that vaccination providers are trained to keep patients seated or lying down for 15 minutes after the vaccine is administered. If you have a history of fainting after injections, let your vaccination provider know before the shot.

How Are TdVax's Side Effects Different from Tenivac or Tdap?

TdVax and Tenivac are both Td-only vaccines with nearly identical compositions and side effect profiles. Tdap vaccines (Adacel, Boostrix) have an additional pertussis component, which may cause slightly more pronounced local reactions in some patients — particularly those who have received multiple prior pertussis vaccinations. However, for most patients, the side effect experience is clinically similar across all these vaccines.

For information on medications that can interact with Td vaccines, see: TdVax Drug Interactions: What to Avoid and What to Tell Your Doctor.

Should You Report Side Effects?

Any adverse reactions to vaccines can be reported to the Vaccine Adverse Event Reporting System (VAERS) at vaers.hhs.gov. Your vaccine administrator is typically required to report certain events. Despite the small risk of side effects, the protection provided by tetanus and diphtheria vaccines far outweighs the risks for most people. If you have concerns about which vaccine is best for you, medfinder can help you locate a pharmacy or clinic near you where you can discuss your options with a healthcare provider.