What are the potential adverse effects of the tetanus (lockjaw) vaccine?

Adverse Effects of Tetanus Vaccine

The tetanus vaccine is extremely well-tolerated, with injection site pain being the most common adverse effect; serious adverse events are exceedingly rare, occurring in fewer than 3 cases per million doses. 1

Common Local Reactions

Injection site reactions are by far the most frequent adverse effects:

• Injection site pain is the most commonly reported adverse event, occurring in the majority of recipients 1
• Local soreness, redness, or swelling at the injection site with temperature less than 40.5°C (105°F) are not contraindications to future vaccination 1
• Medically attended local reactions occur at a rate of approximately 3.6 events per 10,000 vaccinations 2
• Over 80% of reported side effects involve painful reddening and/or swelling at the injection site 3

Systemic Reactions

Fever and constitutional symptoms occur infrequently:

• Fever is reported in 2.4%–6.5% of Tdap recipients, with rates similar between first and second doses 1
• General malaise and increased body temperature account for approximately 10% of reported adverse events 3
• Skin reactions beyond the injection site occur in approximately 3% of cases 3

Serious Adverse Events

Hypersensitivity Reactions

Severe hypersensitivity reactions are extremely rare but can be life-threatening:

• Arthus-type hypersensitivity reactions can occur in persons with high preexisting antibody levels, particularly those receiving frequent doses 1
• Persons who experienced Arthus reactions or fever >103°F (>39.4°C) following a prior dose should not receive tetanus toxoid more frequently than every 10 years, even for contaminated wounds 1
• True IgE-mediated anaphylactic reactions occur at an incidence of approximately 0.001% 4
• In one study, 94 of 95 persons with histories of anaphylactic symptoms were nonreactive to intradermal testing and tolerated full intramuscular doses without adverse effects 1

Neurologic Complications

Guillain-Barré Syndrome (GBS):

• The risk of GBS after tetanus toxoid is extremely low, with only 1 case reported when 2 cases were expected by chance alone in 1.2 million doses 1
• The Advisory Committee on Immunization Practices concluded that tetanus-toxoid-containing vaccines can trigger GBS in adults, but this is exceedingly rare 1
• Persons with a history of GBS within 6 weeks of receiving tetanus toxoid may be at increased risk for recurrence 1
• For such patients, vaccination is usually justified for children with incomplete primary immunization (fewer than 3 doses), but routine booster vaccination probably is not indicated for adults who have received 3 or more doses 1

Brachial Neuritis:

• Tetanus vaccination has been associated with brachial neuritis with a relative risk of 5-10 compared to background incidence 1
• The attributable incidence is approximately one-half to one case per 100,000 recipients 1

Syncope and Dizziness:

• Syncope has been reported in adolescent recipients of Tdap vaccine, with all incidents resolving without sequelae 5
• Patients should be monitored for approximately 15 minutes after vaccination to prevent fall-related injuries 5
• These represent vasovagal reactions rather than direct toxic effects and are not contraindications to future vaccination 5

Risk Factors for Increased Adverse Events

Frequency of prior vaccination significantly impacts adverse event rates:

• The risk of local reactions is 2.9 times higher in persons who received another tetanus-containing vaccine in the previous 5 years 2
• More frequent doses than recommended may be associated with increased incidence and severity of adverse reactions, including Arthus-type hypersensitivity 6
• Young and middle-aged adults with several prior tetanus vaccinations account for the majority of side effects, with hyperimmunization suspected as the cause 3

Safety in Special Populations

Pregnancy:

• Receipt of Tdap during pregnancy is well-tolerated, with no excess risk for severe adverse events 1
• Fever was reported in 1.7%–6.8% of subjects receiving Tdap ≤2 years after Td, with rates comparable to control groups 1
• No evidence exists that tetanus and diphtheria toxoids are teratogenic 1

Repeat Dosing:

• Receipt of a second dose of Tdap at 5- or 10-year intervals is well-tolerated, with adverse event frequency similar to the first dose 1
• Studies on short intervals (within 21 days or ≤2 years) between Td and Tdap found no serious adverse events 1

Critical Clinical Pitfalls

Avoid unnecessary boosters:

• Do not give tetanus toxoid more frequently than recommended, as this increases the risk of Arthus-type reactions 6
• Patients with prior Arthus reactions should not receive tetanus toxoid until >10 years after the most recent dose, even for contaminated wounds 6

Conditions that are NOT contraindications:

• Mild local reactions (soreness, redness, swelling) or fever <40.5°C 1
• Mild acute illness with low-grade fever 1
• Family history of adverse events following vaccination 1
• History of allergies in the patient or relatives 1