From the Guidelines
The TdaP vaccine provides moderate protection against pertussis in adults, with effectiveness ranging from 60-70% initially after vaccination, but this protection wanes significantly within 2-4 years to approximately 30-40% effectiveness.
Key Points
- Adults should receive one dose of TdaP as a replacement for a regular tetanus booster (Td), regardless of when they last received a tetanus-containing vaccine, as recommended by the Advisory Committee on Immunization Practices (ACIP) 1.
- For those who have never received TdaP, it's recommended even if they're up-to-date with tetanus boosters, to reduce the risk of transmitting pertussis to infants and in health-care settings 1.
- The standard adult dose is 0.5 mL administered intramuscularly, typically in the deltoid muscle.
- Protection decreases over time because the acellular pertussis component in TdaP induces a less robust and durable immune response than whole-cell vaccines used previously, as noted in the 2018 recommendations of the ACIP 1.
- This waning immunity explains why pertussis outbreaks can still occur in vaccinated populations.
- Despite its limitations, TdaP vaccination remains important for reducing disease severity and protecting vulnerable populations like infants through cocooning strategies, where vaccinating adults helps prevent transmission to those at highest risk of severe disease.
Recommendations
- Adults aged 19--64 years should receive a single dose of Tdap to replace tetanus and diphtheria toxoids vaccine (Td) for booster immunization against tetanus, diphtheria, and pertussis if they received their last dose of Td >10 years earlier and they have not previously received Tdap 1.
- Adults who have or who anticipate having close contact with an infant aged <12 months should receive a single dose of Tdap to reduce the risk for transmitting pertussis, with an interval as short as 2 years from the last Td suggested 1.
- Health-care personnel who work in hospitals or ambulatory care settings and have direct patient contact should receive a single dose of Tdap as soon as feasible if they have not previously received Tdap, with an interval as short as 2 years from the last dose of Td recommended 1.
From the Research
TdAp Vaccine Protection for Pertussis in Adults
- The Advisory Committee on Immunization Practices recommends one-time tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination for all adults 19 years and older 2.
- A cost-effectiveness analysis of Tdap vaccination for adults aged 19 through 85 in the United States found that the incremental cost-effectiveness ratios (ICERs) for vaccinating US adults with Tdap ranged from $248,000/QALY to $900,000/QALY 2.
- The study found that the lowest cost per QALY was $248,000 for the age 65 cohort, followed by $332,000 for the cohort of age 19, and $477,000 for the age 50 cohort 2.
- Sensitivity analysis showed that the most dramatic changes in ICER occurred when changing the underreporting factor, vaccine effectiveness, and vaccination costs 2.
- While the study suggests that Tdap vaccination may not be as cost-effective as predicted earlier, it remains the best available preventive measure against pertussis 2.
Limitations and Future Research
- Further investigation of the true burden of pertussis disease among adults and the effectiveness of Tdap vaccination in this population is needed to better estimate the impact of Tdap vaccination 2.