Letters. Immunisation does not rule out tetanus  BMJ 2000;320:383 ( 5 February )

Shimoni et al illustrate a needed caution to clinicians: do not exclude a diagnosis of tetanus in a patient who has been fully immunised.1 Their report adds to the list of rare cases of tetanus that have occurred despite complete immunisation. Although the authors state that all reported cases of tetanus in the United States have occurred in people who have not been immunised, this is not altogether true. A catalogue of the 740 tetanus cases reported by the Centers for Disease Control since 1982 discloses that of the minority whose immunisation status was known, 53 cases had completed a primary series, 22 had received their latest booster between five and nine years before, and two had received a booster within five years  
>           Immunisation status of patients with tetanus
>  in the United States reported by the Centers for Disease Control
                      Immunisation    Primary series    Latest booster
Years - No of cases - status known -  completed -  5-9 years, <5years


1995-97    122              56             16             6           2
1989-90    117              57             12             4           0
1987-88    101              46             5              2           0
1985-86    147              NR             9              5           0
1982-84    253              NR            11              5           0

  NR = not reported.  

In light of their patient's adequate immunisation record, Shimoni et al presume that he should have mounted a protective titre of neutralising antibody. With this I agree. But against what, in particular, does this titre confer protectionclinical infection or fatal infection? The understanding of "protection" was derived from animal studies that correlated serum concentrations of tetanus antibody with symptoms of tetanus.2 The threshold of 0.01 IU/ml was established because guinea pigs with titres above this level were protected from fatal tetanus, not from clinical tetanus; six of 45 animals with protective levels developed non-fatal tetanus.3 Similarly, in humans, non-fatal tetanus has been described in 10 out of 64 consecutive patients with antitetanus titres greater than 0.01 IU/ml.4 More recent cases have borne this out.5

A number of rare and exceptional cases of tetanus occur despite adequate immunisation and protective levels of neutralising antibodies. Since tetanus is likely to be fatal if not recognised and treated properly, the caveat from Shimoni et al1 merits repeating: doctors should entertain the diagnosis of tetanus in the proper clinical setting, regardless of the patient's immunisation record.

David R Vinson, staff physician. 
Department of Emergency Medicine, Kaiser Permanente Medical Center,
Sacramento, CA 95825, USA

 1. Shimoni Z, Dobrousin A, Cohen J, Pitlik S. Tetanus in an immunised patient. BMJ 1999; 319:1049[Full Text]. (16 October.)
 2. McComb JA. The prophylactic dose of homologous tetanus antitoxin. N Engl J Med 1964;270: 175-178.
 3. Sneath PAT, Kerslake EG, Scruby F. Tetanus immunity: the resistance of guinea pigs to lethal spore doses induced by active and passive immunization. Am J Hygiene 1937; 25: 464-476.
 4. Goulon M, Girard O, Grosbuis S, Desormeau JP, Capponi MF. Les anticorps antitétaniques: titrage avant séro-anatoxinothérapie chez 64 tétaniques. Nouv Presse Med 1972; 1:3049-3050[Medline].
 5.  Crone NE, Reder AT. Severe tetanus in immunized patients with high anti-tetanus titers. Neurology 1992; 42: 761-764[Medline].

© British Medical Journal 2000

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