The two different formulations of pneumococcal vaccines currently available in the U.S. are pneumococcal conjugate vaccine 7-valent, also called PCV7 and sold as Prevnar® (Wyeth-Lederle), and pneumococcal 23-valent vaccine (Pneumovax 23® [Merck] and Pnu-Immune-23® [Wyeth-Lederle]). The pneumococcal conjugate vaccine 7-valent is a conjugated vaccine, rendering it more immunogenic in infants and children younger than 2 years of age and in patients with immunodeficiencies. The 23-valent vaccine is indicated for use in adults aged 65 or older, immunocompromised adults, and in children older than 2 years of age with chronic illnesses associated with increased risk of pneumococcal disease. PCV7 is administered as a four- injection series, typically starting in the second month of life (see Figure 1). The 23-valent vaccine is administered as a single injection, with booster injections considered every five years. In October 2000, the ACIP recommended that all infants aged 2 to 24 months receive PCV7 as part of their routine vaccination schedule.
Prevnar® has been in short supply since August 2001, when Wyeth-Lederle, the sole manufacturer of PCV7, experienced supply problems, including facility and product testing-related limitations at its production sites, halting the distribution of Prevnar® for several weeks. During the latter half of 2001, only about half of the monthly doses needed in the U.S. were being produced by the manufacturer. The CDC has twice published recommendations for managing the shortage of PCV7. Recommendations for management of the PCV7 include:
- vaccination deferral for all children older than 2 years of age except those at an increased risk of invasive pneumococcal disease.
- deferral of doses to healthy infants and children younger than 24 months of age.
These children should receive a decreased number of pneu-mococcal conjugate vaccine doses on the basis of the age at which vaccination is initiated and the estimated amount of vaccine available to the health care provider’s practice. For example, in the event of a moderate shortage, a three-injection schedule should be used for infants who received their first vaccination before 6 months of age. If a severe shortage were to be experienced, infants receiving their first dose of vaccine prior to 11 months of age would receive only a two-injection series. In addition, children receiving their first vaccination at 12 to 23 months of age would receive only a single dose of PCV7. In either case, initial vaccination of children older than 24 months of age with PCV7 is not recommended. The 23-valent vaccine should be considered an alternative in these older children. These strategies are designed to ensure that adequate supplies of the vaccine are available to initiate abbreviated vaccine schedules in all children rather than leave some children unvaccinated.
Tetanus toxoid (TT) is available as a single-agent product and in combination with either diphtheria alone (Td and TD) or diphtheria and pertussis (DTP). DTP products contain either acellular or whole-cell pertussis. Products containing whole-cell pertussis are designated DTwP; products containing acel-lular pertussis are designated DTaP.
Acellular pertussis vaccine (DTaP) is associated with a significantly lower incidence of local and systemic adverse reactions and better efficacy when compared to DTwP. DTaP is the currently recommended agent for routine vaccination of infants and children, although DTwP remains an acceptable alternative.
DTP is administered as a five-injection series starting at 2 months of age (see Figure 1). The fifth dose (booster) is usually given at 4 to 6 years, before the child enters school. If the fourth dose was given after the child’s fourth birthday, however, a booster dose is not necessary. If a child receives whole-cell pertussis DTP for one or more initial doses, acellular pertussis vaccine may be given to complete the five-dose series.
TD is used to denote the tetanus and diphtheria toxoid used in children under 7 years of age and contains a greater amount of diphtheria toxoid compared with the adult product. Td denotes that the product contains the same amount of tetanus tox-oid but less diphtheria, and it is used for adults and children over 7 years of age to boost immunity. A lower dose of diphtheria is delivered to adults and older children in order to decrease adverse reactions. TT is used in emergency situations and when patients have contraindications to the combination products.
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All tetanus-containing products are currently in some state of short supply. Until recently, Td, TD, and TT were manufactured by Wyeth-Lederle and Aventis Pasteur. Wyeth-Lederle discontinued all products containing tetanus toxoid, leaving Aventis as the sole producer of these two products. Glaxo-SmithKline manufactures a DTaP but no other tetanus-containing product. Aventis has not been able to meet the increased demand left by Wyeth’s exit of the market, thus creating a critical shortage of TT, Td, and TD. The problem has been compounded by issues related to the removal of the preservative thimerosal (mercury) from vaccines following a Joint Statement issued by American Academy of Pediatrics and the Public Health Service in July 1999. The statement established the goal of removing thimerosal from vaccines routinely recommended for infants.
The timing of the shortage of TT, Td, and TD is especially unfortunate, in light of a recently published study demonstrating that only 60% of Americans 6 years of age or older had fully protective levels of diphtheria antibody, and 72% had protective levels of tetanus antibody. The CDC has issued guidance on prioritizing vaccine candidates in order to preserve the existing vaccine supply. These recommendations include the delay of all routine Td boosters in adolescents and adults until resolution of the shortage except:
- persons traveling to a country where the risk for diphtheria is high.
- persons requiring tetanus vaccination for prophylaxis in wound management.
- persons who have received less than three doses of any vaccination containing Td.
- pregnant women who have not been vaccinated with Td during the preceding 10 years.
It is especially important that patients receiving tetanus vaccines for wound management meet the ACIP recommendations for wound management, in order to receive a booster dose. Aventis Pasteur has increased production of the vaccine in an effort to meet the nation’s demand. However, because the vaccine takes 11 months to produce, there will be a lag time before supplies are back up to normal. Currently, hospitals may purchase up to 100 doses of Td vaccine per week from the Aventis Pasteur; private physicians are allowed to order 50 doses per week. DTaP is available on a limited basis from Aventis Pasteur (eight vials per institution per week), or GlaxoSmithKline (30 doses per week). Health care providers should maintain records of patients whose vaccine has been delayed because of the shortage. Health care providers and institutions requiring Td for priority indications should contact Aventis Pasteur.