2012 Antigen Review for the New Zealand National Immunisation Schedule: Diphtheria

Abstract

As a result of the introduction of vaccines against diphtheria, the disease is now rare in developed countries. Evidence suggests that the Diphtheria, Tetanus, acellular Pertussis vaccine (DTaP) is safe and well tolerated in infants, toddlers, adolescents and adults. The adult reduced antigen concentration tetanus-diphtheria (Td) is not associated with any safety concerns in 10-64 year olds or in 65 + year olds. Administration of diphtheria, tetanus, acellular pertussis vaccine (Tdap) to pregnant women is not associated with any unexpected safety patterns in maternal, infant, or fetal outcomes. DTaP vaccines have been proven to be highly immunogenic as primary and booster vaccinations. When the primary series is given during the first few years of life, the antibody levels decrease over time with a booster dose being recommended around pre-school/early school and adolescence age. Adults who have received a primary course also require a booster dose at some time during their adulthood. For people who have never had a primary series of diphtheria vaccines as a child, three doses of the adult formulation vaccine has been found to induce an adequate immune response. The reduced-antigen-content dTpa-IPV vaccine has been found to be non-inferior to full-strength DTPa-IPV vaccine with respect to immunogenicity when administered to pre-school children. The duration of protection from an adult booster dose of diphtheria containing vaccine is unknown as data is limited. Co-administration studies suggest that Tdap vaccine could be co-administered, without compromise of either the reactogenicity or immunogenicity profiles, with Pneumococcal conjugate vaccine containing antigens from 7 pneumococcal serotypes(PVC7), Pneumococcal conjugate vaccine containing antigens from 10 pneumococcal serotypes (PCV10), Pneumococcal conjugate vaccine containing antigens from 13 pneumococcal serotypes (PCV13), HPV16/18, MenACWY and influenza vaccines. New multi-valent combination DTaP vaccines are being developed, including two fully liquid hexavalent vaccines combining diphtheria (D), tetanus (T), acellular pertussis (aP), inactivated polio (IPV), hepatitis B virus (HBV) and Haemophilus influenzae type b (Hib) vaccines; and hexavalent and heptavalent vaccines based around three component aP. Early trials with transcutaneous vaccination patches also sound promising. In developed countries, the primary series of immunisations usually-consists of three doses of DPT vaccine, given at intervals of 4 or more weeks, beginning at 2 or 3 months of age, and reinforced by a fourth dose sometime in the second year of life. The policy of using booster doses of vaccines containing diphtheria toxoid varies considerably. Diphtheria vaccines are well embedded in the immunisation schedule for children and adolescents around the world. Adult booster doses are generally recommended but not always funded and awareness of adult booster vaccines may be low amongst the adult population. Travellers may not be aware of the recommendations for them to have a booster vaccine before travelling to regions where diphtheria is endemic. With respect to diphtheria, the NZ immunisation schedule is in line with international policy and practice.