What is the difference between Td (tetanus and diphtheria) and Tdap (tetanus, diphtheria, and pertussis) vaccines for adults?

Differences Between Td and Tdap Vaccines for Adults

Tdap (tetanus, diphtheria, and acellular pertussis) is preferred over Td (tetanus and diphtheria) for adults who have not previously received Tdap, as it provides additional protection against pertussis while maintaining protection against tetanus and diphtheria. 1

Key Differences

• Components:

  • Td: Contains tetanus and diphtheria toxoids only
  • Tdap: Contains tetanus and diphtheria toxoids PLUS acellular pertussis antigens

• Primary Use:

  • Td: Used for routine booster doses after initial Tdap
  • Tdap: Recommended as a one-time replacement for a Td booster for most adults

Vaccination Schedule for Adults

For Adults with Complete Vaccination History:

1. First adult booster: Tdap (one-time dose)
2. Subsequent boosters: Td every 10 years

For Adults with Unknown/Incomplete Vaccination History:

1. First dose: Tdap
2. Second dose: Td ≥4 weeks after Tdap
3. Third dose: Td 6-12 months later 2

Special Situations for Tdap Use

Wound Management

• Tdap is preferred over Td for adults vaccinated >5 years earlier who require tetanus prophylaxis for wound management and have not previously received Tdap 2
• For adults who have already received Tdap, Td should be used for wound care when indicated
• Adults who completed the 3-dose primary series and received tetanus toxoid-containing vaccine <5 years earlier do not need additional vaccination for wound management

Adults with Close Contact with Infants

• Adults who have or anticipate having close contact with infants <12 months should receive Tdap regardless of when they last received Td 1
• This includes parents, grandparents, childcare providers, and healthcare personnel
• Vaccination should ideally occur at least 2 weeks before beginning close contact with the infant

Healthcare Personnel

• Healthcare personnel with direct patient contact should receive Tdap as soon as feasible if they haven't previously received it 1
• An interval as short as 2 years from the last Td is acceptable for these individuals

Pregnancy

• Women should receive Tdap during each pregnancy, preferably between 27-36 weeks gestation 1
• If not vaccinated during pregnancy, women should receive Tdap immediately postpartum

Safety Considerations

• Both vaccines are generally well tolerated 3, 4
• Local injection-site reactions are the most common adverse events
• Most adverse events are mild to moderate and transient
• Serious vaccination-related adverse events are rare

Common Pitfalls to Avoid

1. Using pediatric formulations in adults: Pediatric DTaP vaccine formulations should never be administered to adults 2

2. Waiting too long between boosters: While the standard interval is 10 years, shorter intervals may be appropriate in certain situations:

   • During pertussis outbreaks
   • For healthcare workers (as short as 2 years from last Td)
   • For adults with infant contact (as short as 2 years from last Td)

3. Assuming prior pertussis infection provides lifelong immunity: Adults with a history of pertussis should still receive Tdap according to routine recommendations, as immunity wanes over time (possibly as early as 7 years after infection) 2

4. Overlooking the need for Tdap in adults: Despite recommendations, Tdap coverage among adults aged 18-64 years was estimated to be only 5.9% in 2008 5

By following these evidence-based recommendations, clinicians can help protect adults against tetanus, diphtheria, and pertussis while also reducing the risk of transmission to vulnerable populations, particularly infants.