Antitoxins for diphtheria and tetanus decline more slowly after vaccination with DTwP than with DTaP: A study in a Chinese population

Objectives

DTP vaccines are used for the prevention of pertussis, diphtheria and tetanus. In 2007, in Gaobeidian city, China, the DTwP vaccine was replaced with DTaP. This study described the diphtheria and tetanus sero-epidemiology in subjects vaccinated solely with DTwP or DTaP.

Methods

Blood samples were obtained between October 2012 and June 2013 from 587 healthy subjects aged 2–17 years. Serum IgG antibodies against diphtheria and tetanus were determined using ELISA. Interrupted time series analyses examined the changes in antitoxin levels over time and analyzed the alterations in diphtheria and tetanus antitoxin levels after the vaccine switch.

Results

Mean concentrations of diphtheria antitoxin and tetanus antitoxin were 0.074 IU/ml (95% CI 0.065–0.084) and 0.063 IU/ml (95% CI 0.053–0.076). The protection rates (antitoxins >0.01 IU/ml) for diphtheria and tetanus were 88.25% and 82.11%. Mean antitoxin levels for both diphtheria and tetanus decreased with increasing age, but this decrease was much slower for DTwP than DTaP.

Conclusions

Although the observed protection rates for diphtheria and tetanus were sufficient to prevent an outbreak at present, the means levels of diphtheria and tetanus antitoxins decreased with increasing age; therefore, booster vaccinations at 7 and 12 years of age would be strengthened in Gaobeidian city, China.     

Immunity to diphtheria and tetanus in England and Wales

The immunity profile of the English and Welsh population to diphtheria and tetanus has been determined by measuring diphtheria and tetanus antitoxin levels for 3088 and 3142 sera, respectively. Time-resolved fluorimetric immunoassay - DELFIA was used to measure diphtheria antitoxin levels and an in-house, indirect ELISA to measure tetanus antitoxin levels. More than 80% of those aged between 2 and 20-24 years had protective diphtheria antitoxin levels of 0.01 IU/ml, or greater, and more than 80% of those aged between 4 and 35-39 years had protective tetanus antitoxin levels of 0.1 IU/ml, or greater. Only 29% and 53% of those aged 60 and over were protected against diphtheria and tetanus. Two increases of diphtheria antitoxin levels greater than 0.1 IU/ml and tetanus antitoxin levels greater than 1.0 IU/ml were apparent, starting at 4 and 14 years of age, which correspond with the policy of giving a diphtheria and tetanus toxoid booster on school entry and a tetanus plus low-dose diphtheria toxoid (recently introduced) booster to school leavers. This is the first comprehensive study of diphtheria and tetanus immunity in the English and Welsh population and shows that the accelerated schedule of immunisation, introduced in 1990, has effectively primed immunological memory against both these antigens and that boosting at school entry and at school leaving is effective in increasing levels of immunity.     

Immune response to a diphtheria and tetanus toxoid administration in a three-dose diphtheria tetanus whole-cell pertussis/enhanced inactivated poliovirus vaccination schedule: a 7-year follow up

The immune response to diphtheria and tetanus toxoid components of a combined diphtheria tetanus whole-cell pertussis/enhanced inactivated poliovirus (DTwP/eIPV) vaccine, administered in a three-dose schedule to infants at 2, 3 and 10 months of age and followed by a booster at the age of 8 years, was compared with the immune profile of a group of children at the same ages given the customary DTwP vaccine schedule at 2, 4, 6, and 12 months of age and a booster at the age of 8. Diphtheria- and tetanus-antitoxin titers were measured in parallel enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay (RIA). After the reinforcing dose given at 10 months of age, diphtheria antitoxin concentrations of 0.01 IU/ml were found in 100% of infants in the study group, 91.7% of whom reached a titer of 0.1 IU/ml and a geometric mean titer (GMT) of 0.40 and 0.93 IU/ml in ELISA and RIA, respectively. At 3 and 6 years of age, diphtheria antitoxin values of 0.01 IU/ml were detected in 100 and 94% of children with GMT of 0.043 and 0.024 IU/ml, respectively. Seropositivity and GMT values indicative of protection were measured by both ELISA and RIA after the booster at the age of 8 years. Similar results were found in the control group, although the GMT tended to be higher. A good correlation between results obtained by ELISA vs. RIA was evident throughout. Priming at 2 and 3 months with diphtheria and tetanus antitoxin, as a component of a DTwP program, and reinforcing 6 months later induced an immune response indicative of protection against the diseases, which persisted up to the age of the booster recommended at school entry.     

Immunity to diphtheria in Siena.

The aim of this study, carried out in 1993, was to evaluate diphtheria immunity in Siena. Diphtheria antitoxin levels were measured by means of the immunoenzymatic test (ELISA) in serum samples of 602 apparently healthy subjects (239 males and 363 females) of all ages residing in Siena. According to widely used criteria, 6% of the total population were susceptible to diphtheria (antibody levels < 0.01 IU/ml), 71% had basic protection (0.01-0.09 IU/ml) and 23% were fully protected (> or = 0.1 IU/ml). The results suggested that a high proportion of young population had a protective level of immunity against diphtheria, that susceptibility increased with age and a smaller proportion of males (2.9%) than females (8.3%) were unprotected; this difference was statistically significant. Our results suggest that it may be useful to revaccinate adults with low levels of diphtheria toxoid so that the percentage that remains unprotected does not put the community at risk of an outbreak of diphtheria.     

杭州市1995--2006年健康人群百日咳白喉破伤风抗体水平监测分析

目的了解杭州市健康人群百日咳、白喉、破伤风抗体水平。方法1995～2006年,在不同区（县、市）,分2～4岁、6～8岁、13～15岁、25～39岁4个年龄组开展百日咳、白喉、破伤风抗体监测。结果百日咳抗体共监测1942人,保护率为93．87％,几何平均摘度为1：1037．36。其中农村2～4岁保护率低于其它三个年龄组,与6～8岁、13～15岁组保护率差异有非常显著的统计学意义（χ^2=8．80、6．13;P均〈0．01）。白喉抗体监测2141人,阳性率91．59％,几何平均浓度（GMC）为0．291国际单位／毫升（IU／m1）。破伤风抗体监测2141人,阳性率72．35％,GMC为0．095IU／ml。结论应加强农村地区的免疫规划管理及预防接种工作。     

Prevalence of IgG diphtheria antitoxin in blood donors in Rio de Janeiro

The lack of information on the immunity of adults in Brazil against diphtheria prompted us to analyse sera from 234 blood donors aged 18-61 years (30.3% females and 69.7% males). IgG diphtheria antitoxin levels determined by means of an ELISA, validated by toxin neutralization test in Vero cells, showed that 30.7% (95% CI 25.0-37.1) of the population was fully protected (>or=1 IU/ml). The highest percentage of subjects fully protected was in the 31-40 years age group. Most of the subjects with uncertain or no protection (<1 IU/ml) were found in the 18-30 years age group (43.8%, OR 2.18, P=0.01). Antitoxin levels were not influenced by the increase in age. Males were more protected than females (80.5%, OR 0.44, P=0.01). The prevalence of 30% of individuals fully protected against diphtheria in blood donors in Rio de Janeiro supports the fact that immunity to diphtheria among healthy Brazilian adults is inadequate. To avoid diphtheria epidemics in the future the immunity among adults should be raised in the coming years.     

The prevalence of diphtheria immunity in healthy population in Poland

The degree of seroprotection against diphtheria in Poland was evaluated by determination of IgG antibodies to Corymebacterium diphtheriae toxin (IgG-DTAb). The study population consisted of 4,829 healthy subjects aged from 1 day to 85 years from 7 regions of Poland. Serum samples collected between 1996 and 1998 were assayed for IgG-DTAb antibodies using a toxoid enzyme immunoassay. Neutralization of toxin in Vero cells was performed as a reference method with the WHO standard for human diphtheria antitoxin. The study revealed a lack of seroprotection (IgG-DTAb < 0.1 IU/ml) in 23% of individuals, basic seroprotection (0.1-1.0 IU/ml) in 64%, and effective seroprotection (> 1.0 IU/ml) in 13%. The non-protected group consisted of non-vaccinated children below 2 months of age (10%), individuals between 2 months and 18 years old (20%) and greater than 19 years old (70%). Of the adults, 32% were seronegative, 63% had basic seroprotection and only 5% were fully protected; 43% of adults between 30 and 64 years, who had not been vaccinated at least during the previous 10 years were not protected against diphtheria. The geometric mean titre (GMT) of IgG-DTAb was 0.25 IU/ml in the total population. Age-related GMTs differed significantly from each other and were higher (0.44 IU/ml) in individuals from 2 months to 18 years old, compared with 014 IU/ml and 0.17 lU/ml in children under 2 months and adults, respectively. No significant difference was found in the GMTs of men and women in all age groups. We conclude that the currently used vaccination programme in Poland is highly effective and assures protection against diphtheria in the majority of the population in the 10-year period following the last booster. However, a significant proportion of adults between 30 and 64 years lack protection and this indicates a need for booster immunization for this group.     

Immunity to diphtheria in Izmir, Turkey

In order to assess immunity to diphtheria in Izmir, Turkey, a total of 743 persons 1–70 years of age were selected with cluster sampling. The information on socio-demographic characteristics, vaccination status and diphtheria history was gathered for each participant. Diphtheria antitoxin levels were measured qualitatively by using micro-enzyme immune assay. Of studied population, 79.1% had fully protective antitoxin levels ( 0.1 IU/ml). Diphtheria protection rates showed a gradual age-related decrease, reaching minimum in the 30–44 age group, in which 40.2% of these subjects had antibody titre below the full protective level. The diphtheria antitoxin geometric mean titer was highest in the 5–9 year age group (1.05 IU/ml). Then, geometric mean titer decreased with increasing age, and reached the minimum level in the 30–44 age group (0.19 IU/ml). These results suggest that in Izmir, Turkey, full serological protection against diphtheria is only detectable in 60% of the adult population. The enhancement of diphtheria immunity by booster vaccinations in adolescents and adults should be considered in Turkey.     

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 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.     

嘉兴市健康人群百日咳、白喉、破伤风抗体水平监测

目的了解嘉兴市健康人群百日咳、白喉、破伤风抗体水平状况。方法采用分层随机抽样方法，抽取4个年龄组健康人群220名，用试管凝集试验检测百日咳凝集抗体，用间接血凝试验检测白喉、破伤风抗毒素。结果百日咳抗体保护率为91．10％，GMT 1：887．13；白喉抗毒素保护率为97．60％，GMT 0．4283 U／ml；破伤风抗毒素保护率为95．70％，GMT 0．3097 U／ml。结论嘉兴市健康人群对百日咳、白喉、破伤风已形成了良好的免疫屏障。     

Seroprevalence of diphtheria immunity among injured adults in Austria

Over a period of 1 year a seroepidemiological study was conducted at the outpatient clinic of a trauma department. Immunity to diphtheria was determined in serum samples from 558 injured patients (205 women and 353 men, age from 18 to 70). Diphtheria-antitoxin concentrations were measured with an enzyme immunoassay and a tissue culture toxin-neutralization assay. Sero-immunity was classified as susceptibility (<0.01 IU/ml), basic protection (0.01-<0.1 IU/ml) and full protection (>/=0.1 IU/ml) against the toxic manifestations of the disease. A total of 27.1% of the subjects were susceptible to diphtheria, 26.5% had basic protection, and 46.4% were fully protected. The median antitoxin concentration reached 0.08 IU/ml (0. 0-0.29; quartiles Q25-Q75). A non linear trend toward decreasing immunity with increasing age was observed (P<0.001) and females proved less protected than males (P=0.006). The country of original immunization (Austria, Western European countries, Eastern European countries and Non European countries) had no influence on sero-immunity (P=0.49). Multiple linear regression analysis revealed that age (P<0.001) and gender (P=0.004) had a significant independent influence on diphtheria immunity level, whereas the country of original immunization was not significant (P=0.72).     

The primary serological response to a single dose of adsorbed tetanus toxoid, high concentration type

Single-dose immunization against tetanus was studied in 511 previously non-immunized residents of rural villages in Upper Volta. Males and females were equally represented and a wide age range was covered. A single dose of adsorbed tetanus toxoid containing 17.5 Lf units of toxoid and 3.86 mg of aluminium phosphate per 0.5 ml dose was used. Blood samples were taken 7 days, 2 months, and 12 months after immunization, and serum antitoxin titres were determined by neutralization titrations in mice. Adverse reactions were negligible. Only 2 participants gave evidence of prior immunization by developing detectable antitoxin titres after 7 days; they were eliminated from the study. After 12 months, 59% of the participants had antitoxin titres of ≥0.01 IU/ml, a titre usually considered protective. The mean titre and the proportion of those protected decreased substantially with increasing age; overall, females gave somewhat greater serological responses than males. Mean titre increased by 25% between 2 months and 1 year after immunization; the increase was greater in females than in males. In children under 6 years of age, 100% of females and 82% of males had protective titres after 1 year.     

A multicentre serosurvey on diphtheria immunity in a French population of 1004 subjects

Diphtheria immunity was determined in serum specimens obtained in 1994 from 1004 subjects seen in emergency departments of three distant French cities. An enzyme immunoassay was used to measure serum diphtheria antitoxin concentrations according to the following criteria: (a) antitoxin < 0.01 IU/ml: susceptibility, (b) 0.01–0.09 IU/ml: basic protection, (c) 0.10 IU/ml: full protection. Among these patients, 20.3% were fully susceptible to diphtheria, 30.3% had basic but doubtful protection and only 49.4% were fully protected. Protection was different by age-groups: 73.5% of the subjects under 40 years of age, 46% between 40 and 65 and 33% over 65 were fully protected. Protection decreased with increasing age (p < 0.001)and was greater for men than women after 40 years of age (p < 0.001). The results of this exploratory study indicate that the enhancement of diphtheria immunity by boosters in adult population should be reconsidered in France as well as in many industrialized countries.     

临沂市健康人群白喉和破伤风抗体水平调查

目的为有计划地进行人群抗体水平监测,了解人群免疫状况,为制定免疫对策、评价免疫效果提供依据。方法采用分层随机抽样的方法,2001、2003、2004年调查了临沂市10个县(区)0~39岁847人的白喉和破伤风抗体水平。结果白喉和破伤风抗体总阳性率分别为77.80%和74.03%,阳性率均是0~4岁组最高,20~39岁组最低;山区县低于平原县和市区。白喉和破伤风抗体几何平均浓度分别为0.0997U/ml和0.0674U/ml,均是8~10岁组最高,20~39岁组最低。结论临沂市白喉和破伤风疫苗基础免疫的效果可靠,但随着年龄的增长,免疫力衰退而重新成为易感者,故应及时对成人加强百日咳、白喉的免疫,并在新生儿破伤风高危县区对育龄期妇女开展破伤风疫苗免疫。     

临沂市健康人群白喉和破伤风抗体水平调查

目的 为有计划地进行人群抗体水平监测,了解人群免疫状况,为制定免疫对策、评价免疫效果提供依据。方法 采用分层随机抽样的方法,2001、2003、2004年调查了临沂市10个县（区）0-39岁847人的白喉和破伤风抗体水平。结果 白喉和破伤风抗体总阳性率分别为77.80%和74.03%,阳性率均是0-4岁组最高,20-39岁组最低;山区县低于平原县和市区。白喉和破伤风抗体几何平均浓度分别为0.0997U/ml和0.0674U/ml,均是8-10岁组最高,20-39岁组最低。结论 临沂市白喉和破伤风疫苗基础免疫的效果可靠,但随着年龄的增长,免疫力衰退而重新成为易感者,故应及时对成人加强百日咳、白喉的免疫,并在新生儿破伤风高危县区对育龄期妇女开展破伤风疫苗免疫。     

Diphtheria antitoxin titres six years after basic immunization of adults

Diphtheria antitoxin titres were analysed in 160 adults (median age 59 years, range 34–70), who completed basic vaccination with three doses of 7.5 Lf or 15 Lf of diphtheria toxoid (D) in a previous vaccination trial in 1987, in serum samples drawn 6 years later. The median titre had decreased from 3.2 IU ml⁻¹ in the post vaccination samples to 0.2 IU ml⁻¹ after 6 years in the 15 Lf group and 0.1 IU ml⁻¹ in the 7.5 Lf group. An antitoxin titre of <0.01 IU ml⁻¹, a level usually considered to give no safe protection, was found in 21/73 (29%) individuals, who had received 7.5 Lf and in 12 of 87 (14%), who received 15 Lf diptheria toxoid (P<0.05). In the orginal study, the vaccinees were enrolled as unimmunized based on their own vaccination histories, but many participants had serological evidence of previous immunization. In the subgroup of 48 truly nonimmune participants, i.e. without prevaccination titres and without booster response after the first injection, 46% (32% in the 15 Lf group and 58% in the 7.5 Lf group) had antitoxin levels of <0.01 IU ml⁻¹ 6 years after basic vaccination. Therefore, individuals who have received basic vaccination with three doses of diphtheria toxoid need at least one booster injection 5–10 years later.     

Immunity to diphtheria in a sample of adult population from central Italy

A sample of 643 healthy subjects from central Italy aged 20 to 80, were screened for diphtheria antitoxin. Serum diphtheria antitoxin was assayed by a new passive haemagglutination technique using turkey red blood cells sensitized with diphtheria toxoid, after having performed a correlation study between this technique and the reference in vivo neutralization test. Of the studied population 26.7% showed a lack of serum antitoxin titres considered to be protective. The rate of susceptible subjects increased with age, showing the highest value (38.9%) in the sixth decade of age. Males proved less protected than females; 53.2% of the male population aged 50-59 were lacking a protective anti-diphtheria immunity. On the basis of present results, a periodical revaccination of the entire adult population with reduced doses of diphtheria toxoid would be advisable.     

河南省健康人群白喉和破伤风抗体水平调查

目的为有计划地进行人群抗体水平监测,了解人群免疫状况,为制定免疫对策、评价免疫效果提供依据。方法采用分层整群随机抽样的方法,1998~2002年调查了河南省21个县(区、市)2~39岁3 510人的白喉和破伤风抗体水平。结果白喉和破伤风抗体总阳性率分别为80.5%和77.9%,阳性率均是2~3岁最高,25~39岁最低;山区县低于平原县和市区。白喉和破伤风抗体几何平均浓度分别为0.101IU/ml和0.073IU/ml,均是8~9岁最高,25~39岁最低。结论河南省白喉和破伤风疫苗基础免疫的效果可靠,但随着年龄的增长,免疫力衰退而重新成为易感者,故应及时对成人加强白喉疫苗的免疫,并在新生儿破伤风高危县对育龄期妇女开展破伤风疫苗免疫。     

Anti-diphtheria immunity in Nigerian mothers and their newborns

Background

Immunity to diphtheria has been noted to wane with age such that previous studies have shown that a significant proportion of females with characteristics comparable to those of Nigerian women of reproductive age have inadequate levels of immunity to diphtheria. Thus, it is envisaged that Nigerian newborns may inherit inadequate levels of immunity to diphtheria from their mothers.

Methods

Cord blood and peripheral maternal blood samples were collected from 231 mother–infant pairs at delivery. Anti-diphtheria antibody titres were assayed using Enzyme-linked immunosorbent assay (ELISA) technique. Recruited babies were those born at term with normal birth weight.

Results

As much as 29.9% of both mothers and their babies had no protection (antibody titre < 0.01 IU/ml) from diphtheria. Ninety (39.0% CI 33%,45%) mothers and 107 (46.3% CI 40%,52%) babies were inadequately protected (antibody titre < 0.1 IU/ml) from diphtheria. The difference in the geometric mean antibody titres of mothers and babies was statistically significant (p < 0.0001). There was a strong positive linear correlation between maternal and newborn antibody titres (“r” = 0.983, p < 0.0001), such that, as mothers antibody titres increased those of their babies also increased.

Conclusion

Significant proportions of Nigerian mothers and newborns are at risk of developing diphtheria. Vaccination of parturient women with booster doses of diphtheria toxoid vaccine is recommended.     

Evaluation of diphtheria convalescent patients to serve as donors for the production of anti-diphtheria immunoglobulin preparations

AIMS: The study was conducted to evaluate the possibility of selecting convalescent diphtheria patients to serve in emergency situations as donors for the production of anti-diphtheria immunoglobulin. To select suitable donors, the criterion of an antitoxin titer >/=3.0 IU/ml was used. In addition, the effects of treatment and the effect of immunization with diphtheria toxoid on the level of anti-diphtheria toxin antibodies were evaluated. SCOPE: Three groups of diphtheria patients were included in the study. The first group (n = 23) consisted of patients who had a basic antibiotic treatment, with or without serotherapy using horse antitoxin and/or human immunoglobulin. The second group (n = 12) comprised patients examined immediately after the onset of disease. The immunological history of this group was not known. The third group (n = 20) included patients with a known immunization history, treated only with antibiotics but having received a booster immunization with diphtheria toxoid. Antitoxin titers were measured using the toxin binding inhibition (ToBI) assay. CONCLUSIONS: In the first group, 47.8% (11/23) of the patients had a diphtheria antibody titer >/=3.0 IU/ml. For most of them, however, the antibody titers could have resulted from treatment with exogenous antibodies from horse antitoxin or human immunoglobulin (18/23). Only two of the 11 high-titer subjects had received antibiotics only. Among the second group, only two (16.76%) of the patients had an antibody titer of >/=3.0 IU/ml. In the third group 50% (10/20) of the patients showed an antibody titer of >/=3.0 IU/ml prior to vaccination, and therefore could be directly considered as donors. Three weeks after booster vaccination, 70% (14/20) had an antibody titer of >/=3.0 IU/ml and 1 year after booster vaccination, 28.6% (2/7) of the subjects still had titers of >/=3.0 IU/ml. In 40% of these patients, a decrease was observed 3-4 weeks after the booster dose. It was concluded that convalescent diphtheria patients could be considered as donors in an emergency situation, since approximately half of them showed antitoxin titers of >/=3.0 IU/ml.