Editor—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 (table).
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 protection—clinical 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.
Table.
Immunisation status of patients with tetanus in the United States reported by the Centers for Disease Control
| Years | No of cases | Immunisation status known | Primary series completed | Latest booster
|
|
|---|---|---|---|---|---|
| 5-9 years | <5 years | ||||
| 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.
References
- 1.Shimoni Z, Dobrousin A, Cohen J, Pitlik S. Tetanus in an immunised patient. BMJ. 1999;319:1049. doi: 10.1136/bmj.319.7216.1049. . (16 October.) [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.McComb JA. The prophylactic dose of homologous tetanus antitoxin. N Engl J Med. 1964;270:175–178. doi: 10.1056/NEJM196401232700404. [DOI] [PubMed] [Google Scholar]
- 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. [Google Scholar]
- 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. [PubMed] [Google Scholar]
- 5.Crone NE, Reder AT. Severe tetanus in immunized patients with high anti-tetanus titers. Neurology. 1992;42:761–764. doi: 10.1212/wnl.42.4.761. [DOI] [PubMed] [Google Scholar]