Diphtheria Vaccination

See also our record on Diphtheria.

Classical diphtheria disease is an acute communicable respiratory infection. Symptoms are caused by the effects of the exotoxin produced by strains of Corynebacterium diphtheriae and occasionally C. ulcerans.
Vaccination confers protection against disease by production of antibodies to the diphtheria toxin. The vaccine is produced from purified inactivated toxin from a strain of C. diphtheriae.¹

Elimination of diphtheria requires a minimum immunity rate of 90% in children and 75% in adults.
The WHO states that 95% of British children should have received primary diphtheria immunisation by 2 years of age.² This target was met in England and Wales in the mid 1990s when an uptake of 96% was achieved. Since then the national coverage rates have decreased slightly with average uptake of 94% in 2004.³ Notably however, within that cohort 11% (33/294) of primary care organisations reported less than 90% coverage, which poses a threat to disease control.⁴

After the primary course of immunisation 94-100% of individuals have protective serum antibody levels. However, serum antitoxin titres fall steeply with time unless boosted with further toxoid.⁵ The efficacy of diphtheria vaccination after a further 2 boosters is approximately 92%.⁶

Immunisation against diphtheria was introduced in the UK during the 1940s.
The incidence of diphtheria then rapidly declined, with only 6 deaths in 1957 compared with 3283 in 1940.¹ Since 1985 there have been only 2 deaths from diphtheria in England and Wales.³

During the 1990s there was a diphtheria epidemic in the republics of the former USSR and the disease is still common in many developing countries. Indeed most cases of diphtheria reported in the UK in recent years, have occurred in travellers returning from Africa and the Indian subcontinent.¹

Recently, strains of non-toxigenic C. diphtheriae, which cause atypical symptoms such as endocarditis and septic arthritis, have emerged in Europe. As the diphtheria exotoxin is not produced, vaccination does not provide immunity. The survival of such strains may be selected by extensive vaccination coverage.⁷

Diphtheria vaccines are available in 2 strengths according to dose of toxoid:

• High-dose - vaccines contain > 30iu of diphtheria toxoid and are used to achieve satisfactory primary immunisation of children - as in DTaP vaccine (capital D= high dose).
• Low-dose - vaccines contain only 2iu of toxoid and are used for primary immunisation of those aged over 10 years and subsequent boosters (lower case d signifies low dose as in dTaP).

Monovalent diphtheria vaccine is not available. Vaccination should only given as a component of the following combination products,

• Diphtheria/ tetanus/ acellular pertussis/ inactivated polio/ Haemophilus influenzae type b vaccines (DTaP/IPV/ Hib)
• Diphtheria/ tetanus/ acellular pertussis/ inactivated polio vaccines (DTaP/ IPV or dTaP/IPV)
• Tetanus/ diphtheria/ inactivated polio (Td/IPV)

Five doses of a diphtheria-containing vaccine are given intramuscularly. Upper arm or anterolateral thigh sites are recommended to minimise risks of local reactions. Other vaccinations such as MMR, MenC or Hepatitis B can be given at the same time but should be injected at an alternative site and preferably in a different limb.

Primary immunisation

All infants should receive the primary immunisation course involving 3 doses of diphtheria-containing vaccine. It is recommended that DTaP/IPV/ Hib be given at 2, 3 and 4 months of age, as levels of passively acquired maternal antitoxin decline. However if necessary the same dosing schedule can be used in children up to 10 years of age. Older individuals should receive 3 doses of a d-containing preparation (usually Td/IPV) at monthly intervals.

Boosters

The first booster dose is given to children between the ages of 3 1/2 and 5 years. Either DTaP/ IPV or dTaP/IPV will elicit an adequate immune response. If primary immunisation has been delayed, the first booster dose must be given at least one year after completion of the initial course. All individuals aged over 10 years who require a first booster should be given a dose of Td/IPV.

The second booster dose is offered to 13 to 18 year olds by the school health service. The Td/IPV preparation should always be used. If previous doses have been delayed, the second booster should be given at least 5 years after the first booster. Note that patients may have inadvertently already received a diphtheria booster associated with tetanus toxoid.

Immigrants¹

Children from developing countries may not be fully immunised against diseases such as diphtheria. If the history is unclear, children are considered unimmunised and should complete the full UK schedule.

Travellers⁸

Travellers to endemic areas should be fully immunised according to the UK schedule before travel. Travellers to developing countries for over one month duration, who had their last diphtheria booster dose more than 10 years ago, should be offered a further booster of Td/IPV.

Laboratory and healthcare workers¹

Individuals who may be exposed to diphtheria at work must be fully immunised and should be offered a booster dose. Further boosters should be given every 10 years if risks persist. Workers who are unimmunised should undergo the complete vaccination schedule with subsequent antibody testing as proof of immunity.

Contacts⁹

Close contacts of a diphtheria case should be offered full immunisation or a booster if their most recent vaccine dose was more than 12 months ago.

The diphtheria vaccination should not be administered to patients with:

• Confirmed anaphylactic reaction to diphtheria toxoid-containing vaccine
• Confirmed anaphylactic reaction to neomycin, streptomycin or polymycin B
• Acute illness with systemic upset and fever
• Evolving or undiagnosed, deteriorating neurological abnormalities

The following situations do not prohibit diphtheria vaccination:

• History of a stable neurological condition, seizures or febrile convulsions (without neurological deterioration)
• Fever, persistent screaming, severe local reactions or hypotonic-hyporesponsive episodes following previous diphtheria vaccinations
• Immunosuppression including HIV infection (but individuals may not achieve an adequate immunological response)
• Pregnancy or breast-feeding

• Pain, swelling, redness or a transient nodule at injection site may occur
• Fever, convulsions, screaming, pallor, cyanosis and hypotonic-hyporesponsive episodes
• Allergic reactions and very occasional anaphylactic episodes

There is no evidence for any association between the DPT vaccine and autism.¹⁰