Serosurveillance of Vaccine Preventable Diseases and Hepatitis C in Healthcare Workers from Lao PDR

Background and Aims

Healthcare workers (HCW) have an increased risk of exposure to infectious diseases and are a potential source of infections for their patients. The Lao People’s Democratic Republic (Lao PDR) has no national policy regarding HCW vaccinations and routine vaccination coverage is low within the general population. This cross-sectional serostudy determines the level of exposure and risk of infection in Lao HCW against 6 vaccine preventable diseases and hepatitis C.

Methods

1128 HCW were recruited from 3 central, 2 provincial and 8 district hospitals. Sera were tested by ELISA for the presence of antibodies and antigens to hepatitis B, hepatitis C, measles, rubella, varicella zoster, tetanus and diphtheria.

Results

Only 53.1% of the HCW had protective anti-hepatitis B surface antigen antibodies (anti-HBs) with 48.8% having anti-hepatitis B core antibodies (anti-HBc), indicating previous exposure and 8.0% were hepatitis B surface antigen carriers. 3.9% were hepatitis C seropositive. Measles and rubella antibodies were detected in 95.4% and 86.2% of the HCW, with 11.9% of females being unprotected against rubella. Antibodies against varicella zoster, tetanus and diphtheria were detected in 95%, 78.8% and 55.3%, respectively. Seroprevalence varied according to age, gender and number of children.

Conclusion

An unacceptably high proportion of Lao HCW remain susceptible to infection with hepatitis B, diphtheria, tetanus and rubella. Furthermore, a high number of healthcare workers are chronically infected with hepatitis B and C viruses. These data emphasize the need for a robust HCW vaccination policy in addition to increased awareness within this subpopulation.     

Expanded program on immunization and its implementation in the Czech Socialist Republic

National immunization programs carried out in the CSR are here confronted with the EPI regional targets for Europe, a component of the WHO global program "Health for all by the year 2000". The EPI target diseases to be brought under control in Europe by 1990 include measles, poliomyelitis, diphtheria and neonatal tetanus; control of congenital rubella infection is to be achieved by the year 2000. The presented data show that Czechoslovakia has succeeded in implementing this program much ahead of the WHO time schedule. The elimination of measles infection was achieved in 1982, poliomyelitis was brought under control in 1961, and the effective diphtheria control has been in effect since the mid-1960s. Cases of neonatal tetanus are absent in the CSR since 1965, the annual incidence of postnatal tetanus is permanently 0.1-0.2 per 100,000 population. The goal of achieving the rubella-free status and thus the elimination of congenital rubella cases at country level is expected to be reached in the early 1990s. Implementation of the remaining WHO recommendations pertinent to infections other than EPI target diseases appears also satisfactory. Regular immunization against whooping cough, one of the oldest immunization programs in Czechoslovakia, succeeded in effectively eliminating this infection in the early 1970s. Selective immunization campaigns against influenza infection, introduced many years ago, help protect, together with a large-scale use of available chemoprophylactics, some 200,000 individuals every year in CSR. The hepatitis B immunization program was started in 1983 and is primarily limited to health service staff, which is in line with the existing WHO recommendations. Inception of the regular immunization program against mumps is planned for the beginning of 1987.     

Vaccination coverage in hard to reach Roma children in Slovenia

The results of the retrospective analysis of data on vaccination coverage in the preschool-aged and school-aged Roma children (436 preschool and 551 schoolchildren) in three geographical regions of Slovenia were analyzed to establish the differences concerning coverage for specific vaccinations: poliomyelitis, diphtheria, tetanus, pertussis, measles, mumps and rubella between the two generation. The data were obtained from health records, immunization records (Vaccination booklet) and National Computerized Immunization System (CEPI 2000). Vaccination coverage was calculated by comparing the number of children eligible for immunization with the number of vaccinated children. This article performs the log-rank statistical test, also known as the Mantel-Haenszel test. Log rang test is comparing survival curves for two generations. Preschool-aged Roma children showed higher vaccination coverage than the school-aged Roma generation. There was no significance difference in the generations of preschool aged and school aged Roma children fully vaccinated against poliomyelitis, diphtheria, tetanus and pertussis. Rubella vaccination was significantly lower in the school aged Roma generation. Only 33% of school aged Roma population received two doses of measles, mumps and rubella vaccine. Vaccination coverage of preschool Roma children in Slovenia against poliomyelitis, diphtheria, tetanus, pertussis and MMR (measles, mumps, rubella) were significantly lower then the national vaccination coverage for preschool aged Slovenia children. Many joint efforts will have to be made to improve the vaccination coverage in Roma communities.     

Immunization

Vaccines have eliminated or substantially reduced the incidence in Canada of smallpox, poliomyelitis, measles, mumps, rubella, diphtheria, tetanus and pertussis. The Canadian Medical Association (CMA) advocates a single immunization schedule, complete for all age groups and diseases where immunization is indicated and available. CMA has endorsed in principle (1984), the second edition of the Guide to Immunization for Canadians compiled by the National Advisory Committee on Immunization and requested that it be disseminated to all practising physicians in Canada. CMA also firmly endorses the concept of a readily accessible nationwide method of recording immunization status. In keeping with the World Health Organization''s commitment to global control of measles, CMA (1981) supports and encourages mandatory vaccination against measles for children. The association advocates a much more aggressive and sustained public education program to promote public awareness and acceptance of immunization.     

不同来源血浆对静注人免疫球蛋白中抗-HBs、白喉抗体效价的影响

调查分析不同来源原料血浆对静注免疫球蛋白(IVIG)制品内的抗-HBs、白喉抗体效价的影响。选择6个单采血浆站,对其提供的血浆为原料制备的IVIG所含的抗-HBs抗体、白喉抗体效价进行了测定。检测结果显示,用A、B、C、D、E、F编号的6个相应血浆站采集的血浆为原料制备成IVIG其抗-HBs抗体(IU/g)效价分别为33.77、103.95、70.94、132.45、78.84、58.28;白喉抗体平均效价分别为5.17、7.36、4.26、7.67、10.14、9.24。6个单采血浆站间的IVIG制品中白喉抗体效价无明显差异,但抗-HBs效价却存有显著差异。     

Alternative diphtheria, tetanus and whooping cough immunization schedule to evoke a Th2 tetanus and a Th1 pertussis immune response

In a previous study, using BALB/c mice, we found that while diphtheria (D), tetanus (T) and whooping cough (Pw, whole-cell Bordetella pertussis) immunization induces a Th1/Th2 tetanus response and memory T cells able to proliferate in response to in vitro stimulation with B. pertussis, DTPa immunization induces a Th2 tetanus immune response and no memory T cells that recognize B. pertussis as stimulus. Considering that a pro-inflammatory cytokine production is not necessary for protection against tetanus and therefore should be avoided, an alternative DTP immunization schedule with minimal Pw exposure was assessed in order to obtain a Th2 tetanus response and a Th1 pertussis response. BALB/c mice were primed with DT vaccine at day 0, with Pw vaccine at day 14 and boosted with DTPa vaccine at days 21 and 28. A control group was inoculated with saline. Antibodies against B. pertussis surface antigens, tetanus and diphtheria toxoids were produced by mice. Spleen cells stimulated in vitro with B. pertussis produced IL-6 and IFNgamma. Only IL-5 was produced by cells in response to tetanus toxoid stimulation. These results are in line with the low IgG1/IgG2a ratio for pertussis antibodies compared with those corresponding to tetanus and diphtheria. The immunization protocol presented herein succeeded in producing tetanus and pertussis immune responses of Th2 and Th1 type, respectively. In contrast to previous results obtained with DTPw immunization, no IL-12 production was observed. Our findings provide direct evidence that an immunization protocol with an interval of 14 days between DT and Pw primings, followed by DTPa boosters, can induce appropriate immune responses against DTP vaccine antigens.     

Evaluation of the reactogenicity and immunogenic potency of combined vaccine "Bubo-Kok" in the immunization of children against diphtheria, tetanus, pertussis and viral hepatitis B

Combined vaccine "Bubo-Kok" is characterized by safety and high immunological activity. The number of postvaccinal reactions in children aged 1 and 2 years, immunized with vaccine "Bubo-Kok", was not statistically different from those in groups of children immunized with adsorbed DPT vaccine, as well with such vaccine in combination with vaccine against hepatitis B. After the completion of the primary course of immunization 100% of children had protective antibody titers against diphtheria, tetanus and hepatitis B. Antibody titers against pertussis, equal to or exceeding protective titers, were found in more than 70% of immunized children. The immunogenic potency of vaccine "Bubo-Kok" with respect to all its components was not inferior to that of adsorbed DPT vaccine and vaccine against hepatitis B, when introduced simultaneously in different areas of the body. Vaccine "Bubo-Kok" successfully passed state trials and was recommended for registration.     

Comparative study of the immunoglobulins and specific antibodies in the blood of rabbits immunized with ADTP vaccine and ADT-anatoxin with normal and reduced antigen contents

Adsorbed DPT vaccine and adsorbed DT toxoids with normal and reduced antigen content were used for the immunization of rabbits. The levels of IgM and IgG and the dynamics of antibodies to diphtheria and tetanus toxins and to Bordetella pertussis in the blood sera of the animals were studied in the postvaccinal period (on days 15 and 34). This study revealed that the reduction of the antigen content of adsorbed DT toxoid to 5 Lf of diphtheria toxoid and 5 binding units of tetanus toxoid did not decrease the capacity of the preparation for increasing the levels of IgG and IgM, antibodies to diphtheria and tetanus toxins in the sera of the rabbits. The reduced content of these toxoids in adsorbed DPT vaccine did not affect its capacity for inducing the enhanced synthesis of IgG, antibodies to diphtheria and tetanus toxins, while the production of IgM and IgA remained unchanged. At the same time an increase in the titers of antibodies to B. pertussis in the animals was less pronounced than that observed after the injection of commercial adsorbed DPT vaccine. Additional investigations are necessary in order to establish the protective potency of the pertussis component in adsorbed DPT vaccine with the reduced content of toxoids and to find out the optimum antigenic composition for this preparation.     

Murine red blood cells as efficient carriers of three bacterial antigens for the production of specific and neutralizing antibodies.

Three bacterial toxoids, CRM 197 (mutagenized diphtheria toxin), tetanus toxoid (formaldehyde-treated tetanus toxin), and PT-9K/129G (double mutant of pertussin toxin) were encapsulated within red blood cells (RBCs) of B6D2F1 and Balb/C mice according to a mild procedure based on hypotonic dialysis-isotonic resealing that yielded undamaged RBCs. The toxoid-loaded RBCs were injected intravenously in order to immunize animals and their effects were compared to those of identical amounts (30-95 micrograms per mouse subdivided into multiple injections) of the corresponding free toxoids injected intravenously in saline. Sera from treated mice were collected and tested for titers of specific antibodies against each of the three antigens and also for titers of neutralizing antibodies, i.e., affording protection from toxic effects induced by the corresponding native toxins. In all experiments, significant seroconversion was observed with both immunization systems. Titers of both specific and neutralizing antibodies against CRM 197 and tetanus toxoid were several-fold higher upon immunization with the RBC-encapsulated toxoids, than with the free toxoids. These differences were not due to qualitatively different recognition patterns of antigenic determinants by the two types of sera. Conversely, intravenous immunization with pertussis toxoid either as RBC-encapsulated or as free antigen elicited a comparably high production of specific and of neutralizing antibodies. These data demonstrate that properly engineered RBCs behave as natural carriers and possibly adjuvants for antigens of vaccinal interest.     

Epidemiological and immunological criteria of the effectiveness of immunization with adsorbed DPT vaccine by the old and new schedules

The study revealed that the immunization of children with adsorbed DPT vaccine from the age of 3-4 months, as compared with the immunization of children from the age of 5-6 months, did not lead to an essential increase in the coverage of children with immunization at the period under study (1970-1983) and did not affect the total level of pertussis morbidity, as well as the proportion of children aged up to 1 year in the total number of pertussis cases. Children immunized at an early age produced antibodies in titers, equivalent to the titers in older children, but their immunity against pertussis, in contrast to their immunity against diphtheria and tetanus, was retained for a shorter period. The injection of adsorbed DPT vaccine at the age of 3-4 months was accompanied by a poorly pronounced increase in the content of IgG, the predominant synthesis of IgM and the suppression of the synthesis of IgA. The shift of the start of vaccination to the age of 3-4 months has probably some immunological grounds for diphtheria and tetanus, but it is premature with respect to pertussis.     

昆明市西山区2009年人群4种免疫抗体水平的监测分析

为了解昆明市西山区2009年健康人群中麻疹IgG、白喉IgG、乙肝表面抗原、乙肝表面抗体、乙脑IgG的免疫水平,评价预防接种效果,按卫生部《预防接种工作规范》(2005年版)人群免疫水平监测方法开展了调查。结果显示,白喉抗体总阳性率57.67%,1～4岁组白喉抗体阳性率为89.71%,白喉疫苗在计划免疫人群中实施效果较好,其它人群未能达到免疫成功率;麻疹抗体总阳性率69.71%,未能达到保护水平,而1～6岁组麻疹抗体阳性率为88.10%,达到计划免疫规程人群抗体阳性率85%的指标;乙肝表面抗原阳性率1.57%,乙肝抗体阳性率75.55%,但1～6岁组抗体阳性率较高,然后随年龄增加而降低;乙脑全人群抗体阳性率为70.53%,经过多次乙脑强化免疫,在人群中构建了较为有效的免疫屏障。西山区四种疫苗预防接种工作在国家免费所针对人群中实施效果较好,学龄前人群抗体阳性率较高,除乙脑疫苗接种人群外其它人群因未开展加强免疫工作,未能形成有效抗体免疫屏障,需定期开展重点人群强化免疫工作。     

Evaluation of the immunological effectiveness of the planned vaccinal prophylaxis of diphtheria and tetanus in Sverdlovsk and Sverdlovsk Province

The level and intensity of antitoxic immunity to diphtheria and tetanus in children and adolescents were determined. The presence of tetanus antitoxin in titers exceeding the protective level in 96.3-98.5% of the examined children and adolescents is indicative of a high actual coverage by immunization. Protective titers against diphtheria were lower. There was no essential difference in the levels of protection in children immunized according to the vaccination schedule and in those immunized with some deviations from this schedule. A considerable part of newborns and children aged 3 months had antibodies to diphtheria and tetanus antitoxins. After the third booster immunization changes in antidiphtheria immunity characteristics occurred only in 2.5% of the vaccines and no changes in antitetanus immunity characteristics were observed.     

青海省2006年14岁以下儿童百日咳白喉破伤风抗体水平监测

调查青海省0~14岁健康儿童百日咳、白喉、破伤风抗体水平,抽样评价预防接种质量。在全省六州一地一市各选择1个县,对0~14岁健康儿童进行抗体检测。结果显示,百日咳、白喉、破伤风抗体阳性率分别为93.42%、94.96%和92.93%。不同地区0~14岁健康儿童百日咳、白喉和破伤风抗体阳性率虽有差别,但都达到较高的抗体水平;个别地区抗体水平低,说明青海省儿童计划免疫工作存在薄弱环节。     

Reactivity, immunogenicity and epidemiological effectiveness of vaccination according to various schemes of immunization against whooping-cough, diphtheria and tetanus]

An extended controlled epidemiological trial was carried out for the purpose of studying the reactogenic properties, immunological and epidemiological efficacy of immunization against whooping cough, diphtheria and tetanus according to a scheme suggested by the authors (AKdeltaC-AKdeltaC-KB) in comparison with the official scheme (AKdeltaC-AKdeltaC-AKdeltaC). There was revealed some increase in the frequency of general reactions in children vaccinated by the experimental scheme; however strong general reactions and local reactions of different intensity were encountered with equal frequency in both groups. Two months after the end of the vaccination significantly higher titres of pertussis agglutinins were revealed in children immunized by the AKdeltaC-AKdeltaC-KB scheme; no significant difference was found in the content of the protective titres of diphtheria and tetanus antitoxins. The duration of preservation of postvaccinal antibodies against all the AKdeltaC-vaccine components and increase in their amount after the first revaccination (in 1.5-2 years) was the same in both the groups of children. A greater epidemiological efficacy of pertussis antigen was revealed by prolonged observation in immunization by the AKdeltaC-AKdeltaC-KB sheme in comparison with immunization by the official scheme (pertussis incidence per 100 thousand children proved to be 12.7 and 71.2, respectively).     

Multiplexed measurement of serum antibodies using an array biosensor

The array biosensor provides the capability for simultaneously measuring titers of antibody against multiple antigens. Human antibodies against four different targets, tetanus toxin, diphtheria toxin, staphylococcal enterotoxin B (SEB) and hepatitis B, were measured simultaneously in sera from eight different donors in a single assay and titers were determined. The assays could measure amounts of bound antibody as low as approximately 100 fg. Each individual serum exhibited a different pattern of reactivity against the four target antigens. Applications of this biosensor capability include monitoring for exposure to pathogens and for efficacy of vaccination.     

Recall Responses to Tetanus and Diphtheria Vaccination Are Frequently Insufficient in Elderly Persons

Demographic changes and a more active life-style in older age have contributed to an increasing public awareness of the need for lifelong vaccination. Currently many older persons have been vaccinated against selected pathogens during childhood but lack regular booster immunizations. The impact of regular vaccinations when started late in life was analyzed in an open, explorative trial by evaluating the immune response against tetanus and diphtheria in healthy older individuals. 252 persons aged above 60 years received a booster vaccination against tetanus, diphtheria, pertussis and polio and a subcohort (n=87) was recruited to receive a second booster vaccination against tetanus, diphtheria and pertussis 5 years later. The percentage of unprotected individuals at the time of enrollment differed substantially for tetanus (12%) and diphtheria (65%). Despite protective antibody concentrations 4 weeks after the first vaccination in almost all vaccinees, antibodies had again dropped below protective levels in 10% (tetanus) and 45% (diphtheria) of the cohort after 5 years. Protection was restored in almost all vaccinees after the second vaccination. No correlation between tetanus- and diphtheria-specific responses was observed, and antibody concentrations were not associated with age-related changes in the T cell repertoire, inflammatory parameters, or CMV-seropositivity suggesting that there was no general biological “non-responder type.” Post-vaccination antibody concentrations depended on pre-existing plasma cells and B cell memory as indicated by a strong positive relationship between post-vaccination antibodies and pre-vaccination antibodies as well as antibody-secreting cells. In contrast, antigen-specific T cell responses were not or only weakly associated with antibody concentrations. In conclusion, our findings demonstrate that single shot vaccinations against tetanus and/or diphtheria do not lead to long-lasting immunity in many elderly persons despite administration at relatively short intervals. Sufficient antigen-specific B cell memory B generated by adequate priming and consecutive booster vaccinations and/or exposure is a prerequisite for long-term protection.

Trial Registration

EU Clinical Trials Register (EU-CTR); EudraCT number 2009-011742-26; www.clinicaltrialsregister.eu/ctr-search/trial/2009-011742-26/AT     

Obtaining monoclonal antibodies to Bordetella pertussis antigens

The immunization of mice with the protein fraction of B. pertussis strain 305 has made it possible to obtain hybridomas producing monoclonal antibodies to B. pertussis antigens. Ascitic fluids containing monoclonal antibodies react in the ELISA in high titers and actively agglutinate B. pertussis strains 305 and 475.     

Neutralization of five subgenotypes of Enterovirus 71 by Taiwanese human plasma and Taiwanese plasma derived intravenous immunoglobulin

Enterovirus 71 (EV71) commonly occurs in children, causing hand, foot and mouth disease (HFMD) in about 29% of patients. Studies have suggested that patients develop meningitis and encephalopathy with a mortality rate of 4–26%. EV71 subgenotypes including B4, B5, C2, C4 and C5 have caused HFMD epidemics in Taiwan. In terms of therapeutical strategy, intravenous immunoglobulin (IVIG) has been shown to improve patient conditions. In this study, the EV71 neutralizing titer was evaluated in 75 human plasmas and 8 lots of Taiwanese plasma derived IVIG. Results showed that human plasmas and IVIG significantly neutralized B4 and C2 subgenotypes. Four percent of human plasma contained neutralizing antibody titer of 1:128 against B4 and C2. Most IVIG lots possessed a median effective dose of over 100 against B4 and C2. IVIG lots had an average neutralizing capacity of 5.60, 0.90, 4.30, 1.12 and 0.77 log₁₀ CCID₅₀/ml against B4, B5, C2, C4 and C5, respectively. In conclusion, effective neutralization of B4 and C2 could be due to their earlier appearance in the EV71 epidemiology timeline of Taiwan. IVIG derived from Taiwanese plasma may be desirable for treatment of patients infected with EV71 of specific subgenotypes.     

采用多种抗原测定静注人免疫球蛋白(pH4)中抗体Fc段生物学活性的初探

目的初步探讨采用多种抗原测定静注人免疫球蛋白(IVIG)(pH4)中抗体的Fc段生物学活性,了解IVIG中抗体的Fc段生物学活性。方法采用补体活化的经典途径中免疫复合物激活补体的方法,将不同浓度的麻疹病毒、风疹病毒、乙肝表面抗原(HBsAg)、破伤风类毒素、脑膜炎球菌P64k外膜蛋白和白喉类毒素6种抗原分别致敏人O型血红细胞形成红细胞-抗原结合物;然后,6种致敏红细胞分别与IVIG孵育,与特异性抗体形成红细胞-抗原-抗体复合物;最后,此复合物与补体反应,在541 nm波长处读取吸光值,并绘制溶血反应动力学曲线,分别计算IVIG中针对上述6种抗原IgG的Fc段生物学活性。采用此方法,用6种抗原致敏的红细胞测定IVIG的Fc段生物学活性10次,验证此方法的重复性。结果麻疹病毒、风疹病毒、HBsAg、破伤风类毒素和脑膜炎球菌P64k外膜蛋白致敏的红细胞分别与供试品和补体反应后,测定的溶血反应动力学曲线较平缓,而白喉类毒素致敏的红细胞与供试品和补体反应后,测定的溶血反应动力学曲线下降明显,呈典型的"S"型曲线。计算结果显示,IVIG中针对此六种抗原的抗体Fc段生物学活性相对于参考品均大于80%。Fc段生物学检测方法重复性较好。结论采用多种抗原分别致敏红细胞,可以用来检测IVIG中多种抗体的Fc段生物学活性,为深入了解IVIG制品中的多种抗体的Fc段生物学活性奠定了基础。     

Postvaccinal antidiphtheria and antitetanus immunity in patients with systemic connective tissue diseases

The retrospective evaluation of the intensity of postvaccinal immunity at different periods after the primary course of immunization against diphtheria and tetanus was made. In the sera taken from 130 children with systemic connective tissue diseases the content of antibodies to diphtheria and tetanus was determined. As revealed in this study, the protective levels of antibodies to diphtheria and tetanus toxoids were retained by both sick and healthy children for 5 years and longer. Significantly lower titers of antibodies to diphtheria and tetanus toxoids were registered in children undergoing therapy with glucocorticosteroids and cytostatics at the time of the study.