Indications and Role:
The vaccine is made from a cell-free purified toxin extracted from a strain of C. diphtheriae and treated with formaldehyde which converts it into a diphtheria toxoid. These are NOT live vaccines and can not cause the diphtheria.
Diphtheria vaccines are produced in two strengths:
- ‘D’ indicates a higher strength of 30 IU (given for primary immunisation in those under the age of 10 years)
- ‘d’ indicates the lower dose of 2 IU
Diphtheria vaccines are only given as part of combined products and are now part of most countries immunisation schedule:
- diphtheria/tetanus/acellular pertussis/inactivate polio vaccine/Haemophilus influenza type b (DTaP/IPV/Hib)
- diphtheria/tetanus/acellular pertussis/inactivated polio vaccine (DTaP/IPV or dTaP/IPV)
- tetanus/diphtheria/inactivated polio vaccine (Td/IPV)
Administration and dosing:
- Vaccines should be injected intramuscularly into the upper arm or anterolateral thigh. This is to reduce the risk of localised reactions which are more common via the subcutaneous route.
- If the patient has a bleeding disorder then a subcutaneous route is preferred.
Dosage immunisation schedule (A total of five doses is considered adequate for long-term protection but remember immunity wains and boosters should be given every 10 years):
- 1st, 2nd and 3rd dose should be given 1 month apart (usually at 2, 3 and 4 months of age as a DTaP/IPV/Hib).
- If this time frame is missed it can be initiated at any time after 2 months of age.
- If the schedule is interrupted it should be resumed and not repeated.
- If starting in a child older than 10 years, the regimen should include vaccines with the ‘d’ combination and give the first three 1 month apart.
- The first booster should be given 3 years after completion of the primary course. Or if there has been delay in the primary course, 1 year after completion.
- The second booster should be given 10 years after the first booster. If there has been a delay in the usual regimen then the second booster may be given 5 years as a minimum interval after the first booster.
- If adults are at risk or travelling to areas of risk then boosters should be given again if one has not been provided within 10 years.
Contraindications or complications and special populations:
- Other vaccines can be given at the same time.
- It is safe in pregnancy and in breastfeeding mothers.
- HIV patients should be discussed with a specialist to review their antibody response.
- Very premature infants </= 28 weeks gestation should be observed in hospital for 48-72 hours post vaccination.
- Uncontrolled seizures in childhood should have their vaccine schedule discussed with a specialist.
- Contraindications include a confirmed anaphylactic reaction to a previous diphtheria containing vaccine or confirmed anaphylactic reaction to neomycin, streptomycin or polymyxin B. The US rates of anaphylaxis are 0.65 – 3 events per million doses of vaccine given.
- The green book – diphtheria