Adult Immunization - Tetanus and Diphtheria

This article discusses tetanus and diphtheria immunization for adults. A future article will discuss influenza and pneumococcal immunization for adults.

Tetanus and Diphtheria

Immunization status is considered an integral part of the health assessment of any adult. Opportunities to provide vaccines to adults are often missed. Prevention of infection by immunization is a lifelong process that should be tailored to meet individual variations in risk resulting from age, underlying illness, lifestyle, occupation and foreign travel.

All Canadian adults require tetanus and diphtheria immunization preferably with Td. It is important to ensure that adults have primary immunization with Td. Adult boosters should be given at 10 year intervals. (Level 4 evidence)

Influenza vaccine and Pneumococcal vaccine are also important for all individuals over the age of 65 years and for those less than 65 years of age with certain high risk medical conditions. (Level 4 evidence) One practical approach to start to increase coverage rates similar to those recommended by several authorities including the American Association of Family Practice would be to consider an age 50 vaccination check where all adults aged 50 should receive a dose of Td vaccine if they have not had a booster within the last 10 years and vaccination should be reviewed if any have high risk medical conditions such as chronic respiratory or cardiac disease for which Influenza or Pneumococcal vaccine is recommended.

History of Tetanus and Diphtheria:

Since tetanus spores occur everywhere in our environment, immunization is the only effective means of protection. In the early 1900's over 5000 cases of tetanus occurred in the U.S. every year. Since 1982, fewer than two (2) cases per year have been reported in Canada.

Prior to 1900, diphtheria was one of the main causes of death of children. Since 1983, there have been fewer than five cases of diphtheria and no deaths from diphtheria in Canada. Most cases in Canada occurred in adults who had been either partially immunized or not immunized at all. In the former Soviet Union there were 839 cases of diphtheria reported in 1989. From 1990 to 1995, approximately 125,000 cases and 4,000 deaths were reported in the Newly Independent States (NIS) of the former Soviet Union. The major reason for the diphtheria epidemic in the NIS has been attributed to a deterioration of the public health immunization programs: low immunization coverage rates among children (related to irregular supply of vaccines, decreased vaccine utilization by health care workers, and a decreased acceptance of immunization by the public and the medical community resulting from anti-immunization propaganda); waning immunity among adults; and large movements of the population following the breakup of the former Soviet Union.

Serology of Canadians

After a primary series of properly spaced doses of tetanus toxoid, essentially all recipients achieve antitoxin levels considered to exceed the minimal protective level of 0.01 IU/ml. Efficacy of the tetanus toxoid has never been studied in a vaccine trial. It can be inferred from protective antitoxin levels that a complete tetanus toxoid series has a clinical efficacy of virtually 100%; cases of tetanus occurring in fully immunized persons whose last dose was within the last 10 years are extremely rare. Following a properly administered primary series, virtually all persons develop a protective level of antitoxin that falls over time. While some persons may be protected for life, most persons have antitoxin levels that approach the minimal protective level by 10 years after the last dose. As a result, routine boosters are recommended every 10 years.¹

In July 1996, an adult immunization survey was done in the Ottawa area by the Laboratory Center for Disease Control (LCDC) Field Epidemiology students.² Weighted estimates of coverage were 50% for tetanus, 60% among those for whom influenza vaccine is recommended (®65 years of age or certain chronic medical conditions).²

Missed opportunities for immunization were frequent: 83% of 94 individuals who had not received tetanus toxoid in the past 10 years reported a visit to their physician in the past year, as did 35% of the 89 influenza vaccine candidates who were not immunized in the previous year.²

In 1996, LCDC and the Canadian Red Cross conducted a serosurvey of a sample of healthy adult blood donors, aged 20 to 80 years, in five Canadian centers.³ Diphtheria antitoxin levels were measured by an in vitro neutralization test. Overall 20.3% (95% CI: 18.4% to 22.4%) of the study population had diphtheria antitoxin levels below the accepted protective threshold of 0.01 IU/mL, raising the possibility of clinical susceptibility. The proportion varied by age group, ranging from 9.5% (6.8% to 13.0%) among those 30 to 39 years to 36.3% (29.7% to 43.3%) in those aged ® 60 years. As well, the proportion of susceptible persons differed by study center, ranging from 13.4% (10.0% TO 17.7%) to 32.2% (26.8% to 38.2%).

In all age groups except these 40-49 years, a higher proportion of males lacked protective antitoxin levels; overall 20.8% (18.5% to 23.2%) of males and 19.0% (15.4% to 23.3%) of females had antitoxin levels < 0.01 IU/mL. Similar low levels of diphtheria immunity were reported in another study of Canadian Red Cross adult donors in Toronto. The frequency of susceptibility ranged from 12.5% to 17.9% among donors <40 years of age to a range of 42.6% and 40% among donors aged ®60 years.³

These recent serosurveys indicate a lack of evidence of immunity to diphtheria among Canadian adults, leading to concerns about the potential for diphtheria to resurface in Canada. The results are particularly important given that these studies were based on relatively healthy populations and therefore the actual levels of immunity in the general adult population are likely to be even lower. The resurgence of diphtheria in parts of Europe means that the possibility for the resurgence of diphtheria in Canada must be considered.³

- Jeff Scott

Thanks to Dr. Graham L. Pollett MD,MHSc,FRCPC Medical Officer Of Health Middlesex London Health Unit, London Ontario for reviewing the draft copy of this article.

References:

1. CDC - ed. Atkinson W.; Humiston S; Wolfe C; Nelson R; Epidemiology and Prevention of Vaccine Preventable Diseases, 5th edition, Jan. 1999.
    
2. LCDC - Adult Immunisation Survey - Ottawa, 1996. Canada Communicable Disease Report: Volume 22-21, November 1, 1996.
    
3. LCDC - Guidelines for the Control of Diphtheria in Canada. Canada Communicable Disease Report. Supplement Vol. 24S3 July 1998

You can search for abstracts of the above references by following this link: PubMed