US Pharm. 2006;5(Student suppl):19-21.     

What are the recommendations for the simultaneous administration of the recently approved combination vaccines containing tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis, adsorbed (Tdap/Boostrix or Adacel) with other vaccines routinely administered to adolescents? What are the appropriate minimum intervals between specific vaccines, namely, the administration of Tdap in relation to the tetanus and diphtheria toxoids, adsorbed (Td/Decavac and others) and the new tetravalent meningococcal polysaccharide diphtheria conjugate vaccine (MCV4/Menactra)?

Background
In January 2005, the recommended childhood and adolescent immunization schedule advises that children receive the diphtheria toxoid, tetanus toxoid, and acellular pertussis adsorbed vaccine (DTaP) at ages 2, 4, 6, and 15 to 18 months and again at ages 4 to 6 years.1 In order for the fourth dose to be given earlier (e.g., when the patient is age 12 to 14 months), a minimum of six months should have elapsed since the previous dose. It is unnecessary to give a fifth dose if the fourth dose was administered to a child on or after his or her fourth birthday.

In addition to the DTaP series, children should receive a Td booster at their preadolescent visit (usually ages 11 to 12 years), providing that they had received the last diphtheria- and/or tetanus-containing vaccines at least five years prior. If the child did not receive his or her Td booster at the preadolescent visit, he or she may receive it at ages 13 to 18 years. Additional boosters of Td should be given every 10 years.1

Two new Tdap vaccines have recently received FDA approval for use as a one-time dose.2,3 Boostrix is indicated for adolescents ages 10 to 18 years.2 Adacel is approved for use in 11- to 64-year-olds, broadening the indication to the adult population.3 To date, there are no official guidelines on the use of these vaccines in either the adolescent or adult populations; however, t he Advisory Committee on Immunization Practices (ACIP) has voted on and released provisional recommendations for the use of Tdap in adolescents.4

According to the provisional recommendations, the two Tdap vaccines can be used interchangeably, depending on availability.4,5 In general, adolescents ages 11 to 18 years who have received the entire DTaP series should receive a single dose of Tdap in place of the Td booster, preferably at their preadolescent visit. This visit provides clinicians with the opportunity to vaccinate children against pertussis as well as meningococcal disease.4,5

In clinical practice, health care professionals face many scenarios that affect vaccination administration. For instance, children may not have received the recommended schedule of vaccinations, or vaccinations may not have been properly documented. Recommendations for addressing these situations are found below.4,5

Clinical Scenarios
Clinical Scenario #1: ACIP recommends that MCV4 and Tdap be administered at the same visit, if both are available.4,5 Diphtheria toxoid is used as a protein carrier for MCV4 and provides an antibody response to diphtheria.4-6 Can the two vaccines be administered together?
Recommended Action: It is important to note that MCV4 is not approved as a vaccination against diphtheria.4-6 Some health care professionals have raised concerns about giving two vaccines containing diphtheria (MCV4 and Tdap or Td) together or within such a short interval, potentially increasing the risk of local reactions. The coadministration of Tdap and MCV4 is being studied.4,5 Because Td and MCV4 have been given together in clinical trials with acceptable rates of local reactions, ACIP states that MCV4 and Tdap can be safely given together.4-6 The benefits of vaccination outweigh the risks of local reactions or missing the opportunity to vaccinate.4,5

Clinical Scenario #2: Either MCV4 or Tdap isin short supply due to production shortages. Should cli­ nicians wait until both vaccines are available?
Recommended Action: Sometimes it is not feasible to administer the MCV4 and Tdap together due to supply shortages. If this is the case:
• The available vaccine should be administered immediately, and the one in short supply can be administered when it becomes available.4,5
• Tdap and MCV4 can be administered at any time before or after each other, and ACIP does not recommend a minimum interval between the two vaccines, although it is continuing to study this issue.4,5

Clinical Scenario #3: The Tdap vaccine is not available due to supply issues. An adolescent is due to receive his or her Td booster vaccine. Should a clinician wait to administer Tdap when it becomes available or administer the Td booster at this visit?
Recommended Action: It is acceptable for practitioners to defer Td vaccination in favor of Tdap if all of the following conditions apply:
• The last dose of tetanus-containing vaccine was within the last 10 years;
• The patient does not require immediate tetanus protection, as in the case of a wound; and
• The patient is likely to return for follow-up care to receive the dose of Tdap when it is available. The clinician must ensure that patient follow-up occurs.4,5

Clinical Scenario #4: An adolescent has already received his or her Td booster. Should a clinician provide pertussis protection with Tdap?
Recommended Action: ACIP encourages clinicians to wait at least five years after a diphtheria- or tetanus-containing vaccine has been given before administering the single dose of Tdap. This minimizes the risk of local reactions; however, ACIP realizes that it is not always clinically feasible to wait.4,5 The provisional recommendations do not define a minimum interval, thus allowing maximum flexibility in administering the vaccines.4,5 Intervals as short as two years were found to be acceptably safe in two Canadian studies involving more than 6,000 students who safely received Tdap, subsequent to vaccination with Td or DTaP.4,5,7

For this reason, the minimum interval may be shortened to less than five years when there is an increased risk of pertussis, including communities with outbreaks of pertussis or households with infants present.4,5 When deciding whether to shorten the minimum interval between Td and Tdap, the benefit of protection should outweigh the risk of local reactions.4,5

Clinical Scenario #5: A child has not received the complete DTaP series. Should a clinician administer Tdap?
Recommended Action: Clinicians may administer one dose of Tdap.2-5 The timing depends on the official labeling of the Tdap formulation. For example, Boostrix may be administered to pediatric patients ages 10 years or older, while Adacel may be given only to patients at least 11 years old.2,3 ACIP does not recommend giving more than one dose of Tdap because it is not FDA approved for subsequent dosing.2-5

Clinical Scenario #6: An adolescent does not have documentation that he or she has had the age-appropriate series of DTaP; diphtheria, tetanus toxoid pertussis (antigens unspecified) vaccine (DTP); diphtheria and tetanus toxoid, adsorbed, pediatric strength (DT); or Td.
Recommended Action: ACIP recommends assuming that the patient has not received the series and administering the following regimen:4,5
• If the child is at least age 10 years, he or she should receive a single dose of the appropriate Tdap formulation.2-5 This should be follow­ed by:
• Td at least four weeks later, followed by:
• A second Td dose at least six months after the first Td dose.
• Any one of these Td doses can be replaced with Tdap, but only one of the three in the series should be Tdap.4,5

Conclusion
Keep in mind that these are only provisional recommendations and will become official once they have been reviewed and published in Morbidity and Mortality Weekly Report ( MMWR). Once official, the MMWR document containing the recommendations will be made available on the CDC Web site: www.cdc.gov/mmwr.4

REFERENCES
1. CDC. Recommended childhood and adolescent immunization schedule--United States, 2005. MMWR. 2005;53(Nos. 51 & 52):Q1-Q3.
2. GlaxoSmithKline. Boostrix package insert. Research Triangle Park, NC; May 2005.
3. Aventis Pasteur. Adacel package insert. Swiftwater, PA; June 2005.
4. CDC. Advisory Committee on Immunization Practices (ACIP) votes to recommend routine use of combined tetanus, diphtheria and pertussis (Tdap) vaccines for adolescents. Available from: www.cdc.gov/nip/vaccine/tdap/tdap_acip_recs.pdf. Accessed September 28, 2005
5. CDC. Immunization update 2005. Available from: www.phppo.cdc.gov/PHTN/webcast/immup2005. Accessed September 28, 2005.
6. Aventis Pasteur. Menactra package insert. Swiftwater, PA; January 2005.
7. FDA. Vaccines and related biological products advisory committee, 102nd meeting, 2005 Mar 15. Available from: www.fda.gov/ohrms/dockets/ac/05/transcripts/2005-4097t1.htm. Accessed September 28, 2005.

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