Saar Kuzi
Alessandra Coutinho Fernandes
William Cope
Richard Tapping
Kashif Ahmad
Reda Sadki
Shubhra Kanti Karmaker Santu
Adam P Rusch
Elizabeth Edwards
Matthew LawFA16 Immunization Module’s Updates
Timing of Vaccinations & Adverse Reactions: DTaP vs. Tdap
Multiple formulations of combination vaccines exist for tetanus, diphtheria, and pertussis. The Td vaccine immunizes against the tetanus and diphtheria toxoids, while DTaP and Tdap also include protection against pertussis. Despite the upfront similarities between the DTaP and Tdap vaccines, differences exist that are important to keep in mind when choosing a formulation.
The primary difference is in the antigenic dosages used in each formulation. DTaP vaccines have a comparatively higher amount of diphtheria toxoid and acellular pertussis antigen. These antigens are reduced in dose per Tdap vaccine.1,3 “D” and “P” are capitalized in DTaP to signify the higher levels of respective antigen present.1
This difference in antigenic dosage also affords differences in protective immunity and adverse effects. Thus, DTaP and Tdap are indicated for use in different populations. DTaP should be used to vaccinate children under 7 years of age because the higher antigen levels present are necessary to mount an adequate initial immune response. Tdap should be used as a booster immunization for children older than 11 years of age and adults, when a reduced antigen dosage is sufficient.1,3 The reduced antigen level also means that the incidence of adverse effects is decreased with Tdap than DTaP, although the type and severity of adverse effects are similar between the two and are mostly localized reactions.1,2,3 Patients who receive DTaP instead of Tdap as a booster do not need to be revaccinated with Tdap, but should be informed of the increased risk of developing side effects. However, a child improperly vaccinated with Tdap instead of DTaP should be revaccinated with DTaP.1,3
Confusion between DTaP and Tdap continues to occur during vaccine administration. Recognition of the differences, in addition to improved labeling and oversight of dosages, should help minimize incorrectly administered vaccines.3
1DeDea, L. The difference between Tdap and DTaP; dabigatran versus warfarin. (2011) Journal of the American Academy of Physician Assistants. 24(1):14.
2Klar, S; Harris, T; Wong, K; Fediurek, J; Deeks, SL. Vaccine safety implications of Ontario, Canada’s switch from DTaP-IPV to Tdap-IPV for the pre-school booster. (2014) Vaccine. 32(48):6360-3.
3Paparella, S. Alphabet soup: confusion between DTaP and Tdap. (2010) Journal of Emergency Nursing. 36(6):570-1.
Thanks for the info! That makes sense that capital letters stand for more antigen; it's more intuitive than the order of the letters. It's good to know that switching the 2 isn't necessarily harmful, but requires revaccination for children and may result in increased side effects for adults. I wonder why children need more antigen than adults to mount an adequate immune response? If adults have a higher proportion of memory cells and a less active thymus, it seems they would be less prepared to deal with a new antigen!
This is a very important post and similar to another that is floating around out there. It is important to know this material and it will come up soon in the Microbiology course as well!
Very interesting update! I had no idea that the capital vs. lower case letters gave information about the relative antigen levels or that there were different risk factors between the vaccines. It's crazy how such small details can make such a big difference!
Interesting! I had heard both words, but I had not realised they were different vaccines; I just assumed it was two ways to reference the same thing. Thanks for the enlightenment @Sara Sun!