Diphtheria antibody levels in the Italian Population

Protection against Tetanus and Diphtheria in Europe: The impact of age, gender and country of origin based on data from the MARK-AGE Study

Due to the successful implementation of vaccination strategies early-life morbidity and mortality due to infectious disease has been reduced dramatically. Vaccines against tetanus and diphtheria are among the most frequently used vaccines worldwide, but various studies in different European countries have shown that protection against tetanus and particularly against diphtheria is unsatisfactory in adults and older persons. In this study we analyzed tetanus- and diphtheria-specific antibody concentrations in 2100 adults of different age from 6 selected European countries (Austria, Belgium, Germany, Greece, Italy, Poland) in order to investigate differences in the level of protection against tetanus and diphtheria across Europe. Our data reveal that tetanus- and diphtheria-specific antibody concentrations vary greatly between countries, which is also reflected in the percentage of persons with antibody concentrations below the protective level (0.1IU/ml), which ranged from 2 to 31% percent for tetanus and 28-63% for diphtheria. In most countries, tetanus- and diphtheria-specific antibody concentrations decrease with age. This phenomenon is more pronounced in countries with generally low antibody levels, such as Italy, Poland and Greece. Interestingly, tetanus-specific antibody concentrations are generally higher in males than in females, which is probably due to vaccination during their military service or more frequent booster vaccinations after injuries, whereas no gender-related differences were found for diphtheria-specific antibodies. In conclusion, our study demonstrates that the European population is not fully protected against tetanus and diphtheria. Measures to improve protection should include a life-long perspective on vaccination, more education to increase awareness of and compliance with vaccination guidelines, and a harmonization of recommendations and incentives across Europe.

Adult vaccination against tetanus and diphtheria: the European perspective

Besides immunizations against influenza, Streptococcus pneumoniae and herpes zoster, which are recommended specifically for elderly people, regular booster vaccinations against tetanus, diphtheria and in some cases pertussis and polio are recommended in many European countries for adults, including elderly people. Vaccination recommendations for adults differ greatly between individual countries and coverage data is scarce. Tetanus-specific antibody concentrations are generally higher than diphtheria-specific antibodies, and a substantial proportion of adults, and particularly of elderly people, do not have protective antibody concentrations against diphtheria. Antibody levels increase upon booster vaccination in all age groups, but diphtheria-specific antibody concentrations remain below protective levels in some older individuals, even immediately after vaccination and long-term protection is frequently not achieved. Future vaccination strategies should therefore include regular and well-documented booster shots, e.g. against tetanus and diphtheria, throughout life.

Evaluation of human antibody responses to diphtheria toxin subunits A and B in various age groups

This study aimed to evaluate human antibody responses to diphtheria toxin subunits in various age groups. Antibodies against the intact diphtheria toxin and the diphtheria toxin subunits A and B were evaluated in 1319 individuals using a double-antigen ELISA. Although high levels of protection (83.6%, 95% CI 79.2-87.4) were found in children and adolescents, the middle-aged adult population was less protected (28.8%, 95% CI 24.3-33.6). An increase in age was associated with a decrease in the frequency of protected individuals in the 0-39-year age group (p <0.001). Anti-subunit B levels correlated well (p <0.01) with levels of antibodies against the intact toxin. In children aged < or =16 years, the intervals at which the peaks in geometric mean titres of anti-subunit B antibodies were observed were found to correlate with the ages at which booster doses are administered. Overall, males appeared to be more protected than females (OR 1.67, 95% CI 1.34-2.08, p <0.001). A small group of individuals had antibody levels of > or =0.1 IU/mL against the intact toxin, but did not have protective antibody against subunit B. Determination of anti-subunit B antibody levels should help in evaluating the effectiveness of diphtheria boosters and other aspects of diphtheria immunity.

Susceptibility to diphtheria in adults: prevalence and relationship to gender and social variables

Recent outbreaks of diphtheria have drawn attention to the re-emergence of this disease. This study investigated susceptibility to diphtheria in north-east Germany and its relationship to gender and social factors. A study population of 4275 individuals recruited for the population-based Study of Health in Pomerania (SHIP) was available for analysis. IgG antibodies against diphtheria toxin were determined by ELISA and were used to define susceptibility to diphtheria (i.e., IgG titres < 0.1 IU/mL). The prevalence of susceptibility to diphtheria was 32.4%. Multivariate analysis revealed 45% increased odds of women being susceptible to diphtheria. Women who had not received diphtheria toxoid vaccination during the previous 10 years had four-fold increased odds of being susceptible to diphtheria toxin compared with unvaccinated men. None of the social factors investigated was associated with susceptibility status. It was concluded that a high proportion of middle-aged adults was susceptible to diphtheria. Women lacked seroprotection more often than men, which might be explained, in part, by gender-specific immune responses following vaccination. There is a need for information campaigns to improve public awareness of these problems.

Effect of monophosphoryl lipid A on antibody response to diphtheria toxin and its subunits

Monophosphoryl lipid A (MPL) was evaluated for its ability to enhance the antibody response to diphtheria toxin and its fragment A and fragment B subunits. BALB/c mice were immunized subcutaneously with 1 Lf of diphtheria toxoid in the presence of 25 microg of MPL on days 0 and 14. Two weeks after the second immunization, sera were obtained from the mice and analysed for antibody response to diphtheria toxin and its subunits. A new ELISA method, developed in our laboratory, was used to measure antibody levels against the toxin, fragment A, and fragment B. It was observed that MPL significantly enhanced antibody responses to diphtheria toxin and its subunits. However, there was no statistical difference between anti-A and anti-B responses. The results indicated that MPL seems to be a potential candidate as an adjuvant for future diphtheria vaccine formulation.

Immunogenicity of a combined diphtheria–tetanus–acellular pertussis vaccine in adults

Two clinical studies were undertaken to evaluate the immunogenicity of an adult-type dTpa booster vaccine (Boostrix by GlaxoSmithKline Biologicals). Blood samples taken prior to vaccination showed that 24.4 and 13.0% of subjects were seronegative for diphtheria and tetanus antibodies, respectively. Moreover, about one-third of the vaccinees had no detectable levels of antibodies to pertussis toxoid (PT) or pertactin (PRN). One month post-vaccination, more than 93% of all individuals, regardless of age or type of vaccine received, had seroprotective antibody levels for diphtheria and tetanus (> or = 0.1IU/ml). In those individuals vaccinated with the adult-type dTpa vaccine (Boostrix), more than 98% were found to be seropositive for antibodies to all three pertussis antigens (PT, filamentous haemogluttin (FHA), and PRN). These data suggest that immunity to diphtheria, tetanus and pertussis (DTP) in adults wanes and that booster vaccination with an adult-type combined dTpa vaccine would boost the serological response to diphtheria antitoxin, tetanus antitoxin and antibodies to Bordetella pertussis PT, FHA and PRN.

Diphtheria immunization rates and the effect of several sociodemographic factors on immunization of children in eastern Turkey

BACKGROUND

One of the aims of the World Health Organization is to eliminate diphtheria in all countries. Thus, it is important to achieve a high level of childhood immunization. The present study was performed to determine the level of child immunization against diphtheria and the effect of several sociodemographic factors on immunization of children aged 0-6 years.

METHODS

Using the cluster-sampling method, 767 healthy children were selected at random from three provinces in eastern Turkey. Children were categorized as completely vaccinated, incompletely vaccinated, unvaccinated or vaccination status unknown. If the child had no immunization card, he/she was categorized as vaccination status unknown.

RESULTS

Of the 767 children, 72.3% were completely vaccinated, 18.3% were incompletely vaccinated and 5.7% were not vaccinated. Vaccination status was unknown for 3.7% of children. As the age of the children increased, the proportion of completely vaccinated children increased and the proportion of non-vaccinated and incompletely vaccinated children decreased. The vaccination rates increased in parallel with the education level of the parents. While the vaccination rate was significantly correlated with the socioeconomic level of the families, it was inversely correlated with sibling number.

CONCLUSIONS

The results of the present study show that the immunization status necessary for the elimination of diphtheria has not yet been reached in eastern Turkey. In immunization programs for children in eastern Turkey, priority should be given to increasing primary immunization levels to 90-95% with three or more doses of diphtheria toxoid.

Immunity to diphtheria among refugees in southern Italy

This study assessed the immune status against diphtheria of a sample of refugees (mainly Kosovars and Kurds) in southern Italy (Puglia). The 54.8% of 1128 subjects showed full protection against diphtheria, 30.1% had basic protection and 15.1% resulted seronegative for antitoxin antibody. Only from 45.9 to 73.9% of 0-10 years old refugees were fully protected while from 12.3 to 24.2% were seronegative to diphtheria with the poorest protection rate among Kurdish children from Turkey. Kosovars showed the highest protection rate to diphtheria whereas data suggest a probable endemic level of diphtheria in Iraq. The screening of refugees revealed a low coverage rate for diphtheria, especially in children, probably due to deterioration of the health service infrastructure or intermittent basic health care in the country of provenience. In terms of public health measures, there is the need of administering booster doses to all refugees coming into Italy and into other host countries to increase the coverage rate against diphtheria. The implementation of the immunization programs against diphtheria in the countries of provenience is also strongly recommended.

Reactogenicity and immunogenicity of adult versus paediatric diphtheria and tetanus booster dose at 6 years of age

We evaluated the reactogenicity and immunogenicity of a booster dose of diphtheria-tetanus vaccine administered at the age of school-entry, comparing a low-dose vaccine (dT) to the standard paediatric dose (DT). Participants were randomly assigned to receive one of the two vaccines; the study was evaluator-blinded. The frequency of side-reactions was similar when comparing the two groups, except when considering local redness and swelling, which were significantly more frequent among the DT group. The post-booster geometric mean titre of diphtheria antibodies in the DT group was twice as high as that in the dT group (14.1 IU/ml versus 7.7 IU/ml; P<0.001). The higher antibody response and the comparable reactogenicity indicate that DT should be used as booster at school-entry, particularly if additional booster doses during adolescence or adulthood are not administered.