Immunity against diphtheria in adults in Poland

Technical and diagnostic performance of five commercial anti-diphtheria toxoid IgG enzyme-linked immunosorbent assay kits

The technical and diagnostic performances of five commercially available enzyme-linked immunosorbent assays for the measurement of anti-diphtheria toxoid IgG antibodies were evaluated. There was good agreement between the relative sensitivities of the five assays, but the relative specificity of one of the assays differed from that of the other four assays. Three of the five assays possessed recoveries of the international reference material NIBSC 00/496 within the range of 90% to 110% at antibody levels >0.1 IU/ml. The data suggest that there are manufacture-dependent differences in relative sensitivity, specificity, and accuracy for the determination of anti-diphtheria toxoid IgG antibodies that could result in different diagnostic interpretations.

Issues related to the decennial tetanus-diphtheria toxoid booster recommendations in adults

In terms of disease prevention, reduction of adverse reactions, and cost benefit studies, a strong case can be made for a policy that focuses on assuring high levels of primary immunization with tetanus and diphtheria (Td) toxoids and abandons the decennial Td booster in favor of a single midlife booster at age 50-65 years. The addition of acellular pertussis antigens to Td for routine use in adults has potential problems in terms of schedule, cost, and possible adverse reactions. Careful risk/benefit studies are necessary to evaluate its effectiveness and priority.

Comparison of four serological methods for the detection of diphtheria anti-toxin antibody

The aim of this study was to compare four serological methods for the detection of Corynebacterium diphtheriae IgG anti-toxin antibodies (IgG-DTAb) in human serum. One hundred serum samples were evaluated for C. diphtheriae IgG-DTAb by four different methods: passive haemagglutination (PHA), latex agglutination test (LA), toxoid enzyme-linked immunosorbent assay (Toxoid-ELISA), and toxin-binding inhibition enzyme-linked immunosorbent assay (ToBI-ELISA). As the external standardisation the neutralisation test for C. diphtheriae toxin in Vero cells (TN Vero) was used. For internal standardisation of IgG-DTAb titres, the WHO standard serum of human diphtheria antitoxin was used. The study revealed a poor correlation between the reference test and the PHA (r=0.34 Pearson's correlation coefficient), an acceptable correlation for the LA (r=0.74), a good correlation for the Toxoid-ELISA (r=0.81) and a very good correlation for ToBI-ELISA (r=0.93). The sensitivity measurements of PHA, LA, Toxoid-ELISA and ToBI-ELISA tests, were 14, 100, 94, 96% respectively and the corresponding specificity characteristics were 86, 76, 94, 90 respectively. Of the four evaluated methods, the ToBI-ELISA could be recommended for scientific and precise laboratory assays of diphtheria antibody levels in humans. For screening purposes the Toxoid-ELISA could be used, but the accuracy of antibody titres below 0.1 IU/ml, considered as the limits of protection, is questionable. Both tests offer very useful alternatives to the in vitro diphtheria toxin neutralisation test in Vero cells. Because of their unsatisfactory correlation and sensitivity as compared to the reference method, PHA and LA should be avoided and replaced by one of the two enzyme immunoassays.

The changing epidemiology of diphtheria in the vaccine era

The epidemic of diphtheria in the Newly Independent States (NIS) of the former Soviet Union has drawn attention to our incomplete understanding of the epidemiology of diphtheria. Many unanswered questions remain concerning the reasons for a resurgence of diphtheria and for the shift in the age of patients and concerning the mechanisms for acquisition of immunity in adults through natural infection under unfavorable living conditions. Other unanswered questions relate to the precise role of socioeconomic factors and hygiene conditions in the initiation, buildup, and spread of the epidemic. Important characteristics of the NIS epidemic can be used to help predict the spread of future diphtheria epidemics. These characteristics include a high proportion of infected adults, a progressive spread of disease from urban centers to rural areas, and transition from initial amplification of disease in groups with high rates of close contacts in focalized, well-distinguished outbreaks to a more generalized epidemic.

Evaluation of the effectiveness of vaccination against diphtheria among medical staff of the chair and the Jagiellonian University Hospital of Infectious Diseases in Cracow, Poland. Some epidemiological observations

In Poland, twenty-five cases of diphtheria, mostly among adults (including five foreigners) in the region adjacent to the eastern border were registered in the years 1992-1996. In 1993-1994, because of the threat of diphtheria infection, 41 healthy members of the medical staff of the University Hospital of Infectious Diseases in Kraków, mainly women aged 25-57 years were immunized with Td and d vaccines with a 6-month interval between courses. Prior to vaccination, 17(41%) individuals showed a lack of diphtheria antibodies as determined with a passive haemagglutination test. 14 of them were aged 30-49 years. Six months after the 2nd dose of vaccine, all seronegative persons had developed a protective level of antibodies. Moreover, all vaccinated subjects showed a statistically significant increase of the antibody titre between the first and last serological examinations.

Immunity to diphtheria in a sample of the Canadian adult population

OBJECTIVE

To assess immunity to diphtheria in a sample of Canadian adults.

DESIGN

A seroprevalence study of a group of plasmapheresis donors was performed over a four-month period in 1996. A convenience sample of 1619 sera was collected to obtain a good distribution by age groups and centres. The determination of diphtheria antitoxin concentrations was performed by neutralization of diphtheria toxin in cell culture.

SUBJECTS

A total of 1619 plasmapheresis donors from Halifax, Quebec City, London, Calgary and Edmonton were studied.

RESULTS

Of the 1619 sera, 20.3% tested showed susceptibility to diphtheria (antitoxin concentration less than 0.01 IU/mL). The proportion of susceptibles increased from 9.5% in subjects 30 to 39 years of age to 36.3% in those 60 years of age or more. The age group 20 to 29 years demonstrated a higher proportion of susceptibles (18.3%) than the next age group (30 to 39 years) in four of the five centres. Significant differences in antibody levels were also observed among the centres. There was no statistically significant difference between sexes.

CONCLUSIONS

Overall, detectable antibody and presumably immunity to diphtheria in the present sample of Canadian adults is relatively good. However, reason(s) for the relatively high proportion of susceptibles in those aged 20 to 29 years of age in certain centres, as well as why Canada has not experienced any diphtheria outbreaks in the past 20 years given these susceptibility levels, should be investigated further.

Diphtheria: epidemiological update and review of prevention and control strategies

The importance of anti-diphtheria immunity in adults through periodic booster doses of vaccine is now increasing after last years diphtheria outbreaks in Newly Independent States (NIS) and Algeria and a few cases found in Europe and USA. Diphtheria cases notified in Italy between 1991-1994 have been reported. In 1995 WHO outlined the need to review vaccination schedules against diphtheria in all countries where gaps occur in the immunity of adults. The main sero-epidemiological studies performed in adults and vaccination schedules against diphtheria in some industrialized countries have been examined. Actual situation and control strategies adopted by WHO in the NIS and implications for other countries have been briefly presented. Finally, guidelines for management, investigation and control of diphtheria have been reported, including CDCs recommendations.

Serological survey on the immunity to diphtheria of the northern Greek population

The recent outbreak of diphtheria in the Newly Independent States (NIS) of the former USSR and the immigration from these high risk areas to Greece prompted us to determine the diphtheria antitoxin levels by enzyme-linked immunosorbent assays (ELISA) in 509 healthy individuals (307 males and 202 females) from northern Greece. The population under study was divided in ten age groups from 1 day to > 60 years old. Diphtheria antitoxin levels of > or = 0.1 IU/ml were considered as protective ones. 44.6% of the examined people were found susceptible. The children up to their twenties seem to be immune to diphtheria in a high proportion (86-88.4%). The diphtheria antitoxin levels declined sharply above this age (17.6% in the age group 21-30 years old). The level of protection in adults appeared to be higher in the oldest group (49%). According to these results, the adults are not properly protected. Booster doses of vaccine for them are recommended to improve the resistance of the northern Greek population from possible infection by toxigenic stains of Corynebacterium diphtheriae, imported or endogenous.

Current situation and control strategies for resurgence of diphtheria in newly independent states of the former Soviet Union

Since 1990, an epidemic of diphtheria has spread throughout the newly independent states of the former Soviet Union, and by 1995 a total of 47 808 cases were reported. During the early stages of the epidemic, adequate control measures were not taken and vaccine was in short supply; possible contributing factors to the spread of the epidemic are the presence of highly susceptible child and adult populations, socioeconomic instability, population movement, and a deteriorating health infrastructure. Although WHO views the epidemic as an International public-health emergency and, together with UNICEF and the International Red Cross, has formulated a strategy to combat the epidemic, the necessary funds have not been made fully available. Current vaccination recommendations also need to be reviewed to ensure that population immunity will be adequate to prevent any resurgence of diphtheria in Europe and North America.

Low prevalence of diphtheria immunity in the population of Florence, Italy

A seroepidemiological study was conducted in 1994 on a representative sample of the population of Florence in order to verify the immunity coverage against diphtheria. Subjects were divided according to sex and age class. Sera from each selected class were at least 1.5/1000 of the residing population. Diphtheria antitoxin was titrated using a quantitative ELISA test. The results show an overall adjusted prevalence of diphtheria immunity (> or = 0.01 IU/ml) equal to 63.7%. Subjects of younger age classes have good protection levels (85.5% immune under 30 years), while only half individuals aged > or = 50 years have antibody titres > or = 0.01 IU/ml. Full protection (antibody titre > or = 0.1 IU/ml) was detected only in a very small proportion of those aged > or = 40 years. Our data show (1) how a recrudescence of diphtheria could theoretically take place in older subjects living in Italy, and (2) stress the importance of periodical re-vaccination of adults.

Diphtheria immunity in UK blood donors

Immunity to diphtheria was determined in serum samples from 1000 UK-born blood donors at the North London Blood Transfusion Centre during a three-month period in 1993; 125 women and 125 men were stratified in 10-year age groups, from 20 to 59. A tissue (vero cell)-culture toxin-neutralisation assay was used to measure serum diphtheria antitoxin concentrations. According to internationally accepted definitions (antitoxin < 0.01 IU/mL = susceptibility, 0.01-0.09 IU/mL = basic protection, and > or = 0.1 IU/mL = full protection), 37.6% of donors were susceptible to diphtheria, 31.5% had basic protection, and 30.9% were fully protected. Log-linear modelling of the influence of age and sex on population immunity showed a significant trend (p < 0.001) of decreasing immunity with increasing age: 25.2% of donors aged 20-29 were susceptible compared with 52.8% of those aged 50-59. There was a small sex effect (p = 0.052); similar proportions of men and women were susceptible, but fewer women had full protection. There was no age-sex interaction on immunity (p = 0.454). Our results suggest that booster immunisation of adults is necessary to increase herd immunity of the adult population.

Diphtheria: changing patterns in the developing world and the industrialized world

In the past, diphtheria was considered one of the most serious childhood diseases because it took a heavy toll in health and life among preschool-aged children. Prior to the widespread availability of diphtheria toxoid, nearly 70% of cases were in children younger than 15 years of age. In the industrialized countries, immunization against diphtheria became widespread in the 1940s and 1950s. This led to a marked decrease in the incidence of diphtheria. There was also a decrease in circulating toxigenic Corynebacterium diphtheriae organisms, resulting in less natural boosting of antibody levels. This had led to gaps in the immunity of the adult population. Since 1990, diphtheria has made a spectacular comeback in several European countries, with a high proportion of cases in adults. In developing countries, immunization of infants with diphtheria toxoid was introduced with the Expanded Programme on Immunization in the late 1970s. Coverage rose slowly to 46% in 1985 and 79% in 1992. Because the pool of immunized persons is not yet large, the process of maintaining immunity still operates through natural mechanisms, including frequent skin infections caused by C. diphtheriae. But recently, several developing countries where coverage has been high for 5-10 years have reported diphtheria outbreaks. These outbreaks have been characterized by high case fatality rates, a large proportion of patients with complications, and their occurrence in both young and older age groups. In all countries, priority should be given to efforts to reach at least 90% coverage with three doses of diphtheria toxoid in children below one year of age. In countries where diphtheria has been successfully controlled, immunity levels should be maintained by booster doses.

Molecular epidemiology of nasopharyngeal corynebacteria in healthy adults from an area where diphtheria vaccination has been extensively practiced

In addition to conventional biochemical tests, a DNA probe specific for Corynebacterium diphtheriae was used to characterize 53 cystinase-positive and urease-negative corynebacteria strains isolated from pharyngeal and nasal swabs obtained from 515 healthy adults living in an urban area of central Italy. No Corynebacterium diphtheriae strain was found. Six "atypical" strains were isolated, which could not be classified in any of the species so far defined in the Corynebacterium genus. These strains appeared to be biochemically close to Corynebacterium pseudodiphtheriticum and genetically close to Corynebacterium diphtheriae, since their DNAs strongly hybridized, under relatively low stringency conditions, with a Corynebacterium diphtheriae-specific probe and since insertion sequences which are usually found in Corynebacterium diphtheriae genomes were also found to be present in their genomes. No one of these six strains was either toxigenic or susceptible to lysogenization by beta-corynephage carrying the tox gene. Therefore, they do not seem to have any epidemiological relevance as possible hosts for beta-phages.