High tetanus antitoxin antibody concentrations in the Netherlands: A seroepidemiological study

A literature review and evidence-based evaluation of the Dutch national immunisation schedule yield possibilities for improvements

National Immunisation Programmes (NIPs) develop historically. Its performance (disease incidences, vaccination coverage) is monitored. Reviewing the schedule as a whole could inform on further optimisation of the programme, i.e., providing maximal protection with the lowest number of doses. We systematically evaluated the performance and strategies of the Dutch pathogen-specific NIP schedules through literature review, assessment of surveillance data and expert opinions. Pathogen-specific vaccinations were categorised according to their strategy of protection: I) elimination or eradication, II) herd immunity or III) 'only' individual protection. The schedule of each vaccine-component was evaluated based on fixed criteria: 1. Is the achieved protection adequate? 2. Is the intended protection achieved? 3. Does the programme include too many or too few doses? 4. Is the timing optimal or acceptable? and 5. Are there drawbacks of the NIP for (part of) the population? Identified issues were explored using surveillance data and literature. Using fixed criteria facilitated comparison between pathogens and revealed opportunities to optimise the Dutch NIP by: i. Reducing the number of polio and tetanus vaccinations; ii. prolonging the interval between diphtheria, pertussis, tetanus, polio, hepatitis B, and Hib vaccine doses for improved effectiveness; iii. Expedite the second measles vaccination from 9 to 2-4 years of age to offer unvaccinated children and primary vaccine failures an earlier chance to be protected; and iv. Delaying the second mumps vaccination to enhance protection in adolescents/young adults. No schedule adaptations were deemed necessary for the vaccines against HPV, rubella, pneumococcal disease, and meningococcal disease. Based on this evaluation the NITAG advised to move the DTaP-IPV-HBV-Hib-booster from age 11 to 12 months, the second MMR-dose from 9 to 2-4 years, replace the Tdap-IPV at 4 years with a Tdap at 5-6 years and move the dt-IPV from 9 to 14 years. Implementation of these changes is planned for 2025.

Investigating sources of non-response bias in a population-based seroprevalence study of vaccine-preventable diseases in the Netherlands

BACKGROUND

PIENTER 3 (P3), conducted in 2016/17, is the most recent of three nationwide serological surveys in the Netherlands. The surveys aim to monitor the effects of the National Immunisation Programme (NIP) by assessing population seroprevalence of included vaccine preventable diseases (VPDs). The response rate to the main sample was 15.7% (n = 4,983), following a decreasing trend in response compared to the previous two PIENTER studies (P1, 55.0%; 1995/1996 [n = 8,356] and P2, 33.0%; 2006/2007 [n = 5,834]). Non-responders to the main P3 survey were followed-up to complete a "non-response" questionnaire, an abridged 9-question version of the main survey covering demographics, health, and vaccination status. We assess P3 representativeness and potential sources of non-response bias, and trends in decreasing participation rates across all PIENTER studies.

METHODS

P3 invitees were classified into survey response types: Full Participants (FP), Questionnaire Only (QO), Non-Response Questionnaire (NRQ) and Absolute Non-Responders (ANR). FP demographic and health indicator data were compared with Dutch national statistics, and then the response types were compared to each other. Random forest algorithms were used to predict response type. Finally, FPs from all three PIENTERs were compared to investigate the profile of survey participants through time.

RESULTS

P3 FPs were in general healthier, younger and higher educated than the Dutch population. Random forest was not able to differentiate between FPs and ANRs, but when predicting FPs from NRQs we found evidence of healthy-responder bias. Participants of the three PIENTERs were found to be similar and are therefore comparable through time, but in line with national trends we found P3 participants were less inclined to vaccinate than previous cohorts.

DISCUSSION

The PIENTER biobank is a powerful tool to monitor population-level protection against VPDs across 30 years in The Netherlands. However, future PIENTER studies should continue to focus on improving recruitment from under-represented groups, potentially by considering alternative and mixed survey modes to improve both overall and subgroup-specific response. Whilst non-responder bias is unlikely to affect seroprevalence estimates of high-coverage vaccines, the primary aim of the PIENTER biobank, other studies with varied vaccination/disease exposures should consider the influence of bias carefully.

Association between season of vaccination and antibody levels against infectious diseases

Vaccination has reduced the disease burden of vaccine-preventable diseases. However, the extent to which seasonal cycles of immunity could influence vaccine-induced immunity is not well understood. A national cross-sectional serosurveillance study performed in the Netherlands (Pienter-2) yielded data to investigate whether season of vaccination was associated with antibody responses induced by DT-IPV (diphtheria, tetanus and poliomyelitis), MMR (measles, mumps and rubella) and meningococcus C (MenC) vaccines in children. In total, 434 children met the inclusion criteria to study DT-IPV immunity, 811 for MMR and 311 for MenC. Differences in log(antibody levels) by season of vaccination were investigated with linear multivariable regression analyses. Seroconversion rates varied according to season of vaccination for rubella (90% of autumn-vaccinated children vs. 99% of winter-vaccinated had concentrations above cut-off levels). Summer-vaccinated boys showed a slower decline of tetanus antibodies (6% per month), in comparison with winter-vaccinated boys. In conclusion, season of vaccination showed little association with immunological protection. However, a number of associations were seen with a P-value of about 0.03; and adding data from a just-completed nationwide serological study might add more power to the current study. Further immunological and longitudinal investigations could help understand the mechanisms of seasonal influence in vaccine-induced responses.

Is there an association between socioeconomic status and immune response to infant and childhood vaccination in the Netherlands?

INTRODUCTION

Socioeconomic status (SES) is a well-known determinant of health, but its relation with vaccine-induced immunity is less documented. We explored the association between SES and immunoglobulin G (IgG) levels against vaccine-preventable diseases in vaccinated children in the Dutch National Immunization Programme.

METHODS

Data from a population-wide cross-sectional serosurvey in the Netherlands (2006-2007) were used. We compared geometric mean IgG concentrations/titers (GMC/T ratios) against measles, mumps, rubella, Haemophilus influenzae type b (Hib), Neisseria meningococcus type C, diphtheria, tetanus, poliovirus types 1,2,3 and pertussis in children of high versus low SES by linear regression analysis. We included 894 children (0-12 years) at one of two timeframes: 1 month to 1 year, or 1-3 years after vaccination. Mother's educational level and net household income served as binary indicators of SES.

RESULTS

Of 58 possible associations of vaccine-induced antibody responses with educational level and 58 with income, 10 (9%) were statistically significant: 2 favouring (that is, with higher IgG levels at) high educational level (for Hib 1 m-1y after vaccination (GMC/T ratio: 2.99, 95%CI: 1.42-6.30) and polio 2 1 m-1y after the 9-year booster dose (1.14, 1.01-1.27)) and 8 favouring low income (polio 1, 2 and 3 1 m-1y after the 11-month booster (0.74, 0.58-0.94; 0.79, 0.64-0.97; 0.72, 0.55-0.95), polio 3 and pertussis 1-3y after the 11-month booster (0.70, 0.56-0.88; pertussis-prn: 0.60, 0.37-0.98; pertussis-ptx: 0.66, 0.47-0.95), mumps and rubella 1-3y after first vaccination (0.73, 0.55-0.97; 0.70, 0.55-0.90), and rubella 1 m-1y after second vaccination (0.83, 0.55-0.90)). After adjustment for multiple testing, none of the differences remained significant. There was no association between SES and proportion of children with protective IgG levels.

CONCLUSION

In this explorative study, we found no consistent association between SES and immune response to vaccination in the Netherlands and no association with protective IgG levels. Additional studies in other settings should confirm this finding.

Comparison of antibody response between boys and girls after infant and childhood vaccinations in the Netherlands

BACKGROUND

Infectious diseases can differ by sex in their incidence, prevalence, or severity of disease. These differences may be induced by sex-dependent immune responses and resulting protection, for example after vaccination. Therefore, this study aims to assess possible sex-differences in immunoglobulin levels (IgG) after infant and childhood vaccination.

METHODS

Data from a national cross-sectional serosurvey conducted in 2006/2007 were used (Pienter 2). We compared IgG levels against measles, mumps, rubella, diphtheria, tetanus, poliomyelitis, pertussis, Haemophilus influenzae type b (Hib), and Neisseria meningitidis serogroup C (MenC) between girls and boys both short term (1 month to 1 year) and long term (1-3 year) after infant and childhood vaccinations, using linear regression analysis. Proportions of boys and girls reaching a protective IgG level were compared using Fishers exact test.

RESULTS

Differences in IgG were found at specific time points after vaccination against measles, mumps, rubella, MenC, and polio. The geometric mean concentration or titer (GMC/T) girls:boys ratios ranged between 1.10 for polio type 1 <1 year after the first childhood booster to 1.90 for MenC <1 year after infant vaccination, indicating higher antibody levels in girls. No significant differences were found between boys and girls for diphtheria, tetanus, pertussis, and Hib at either time point. Proportions with protective levels differed only at 1-3 years after infant vaccination for mumps (82.5% boys vs. 91.9% girls, p = 0.046), and at the same time point for MenC (7.0% boys vs. 18.2% girls, p = 0.015), and polio type 1 (87.8% boys vs. 95.9% girls, p = 0.047).

CONCLUSION

Differences in IgG between boys and girls were generally small and not consistent, neither between pathogens nor within pathogens. If differences were observed, girls were favored over boys. On the whole, the results suggest that there are no major sex differences in protection from the studied pathogens in the Netherlands.

Third national biobank for population-based seroprevalence studies in the Netherlands, including the Caribbean Netherlands

BACKGROUND

This paper outlines the methodology, study population and response rate of a third large Dutch population-based cross-sectional serosurvey carried-out in 2016/2017, primarily aiming to obtain insight into age-specific seroprevalence of vaccine-preventable diseases to evaluate the National Immunization Programme (NIP). In addition, Caribbean Netherlands (CN) was included, which enables additional research into tropical pathogens.

METHODS

A two-stage cluster sampling technique was used to draw a sample of Dutch residents (0-89 years) (NS), including an oversampling of non-Western migrants, persons living in low vaccination coverage (LVC) areas, and an extra sample of persons born in Suriname, Aruba and the former Dutch Antilles (SAN). A separate sample was drawn for each Caribbean island. At the consultation hours, questionnaires, blood samples, oro- and nasopharyngeal swabs, faeces, - and only in the Netherlands (NL) saliva and a diary about contact patterns - were obtained from participants. Vaccination- and medical history was retrieved, and in CN anthropometric measurements were taken.

RESULTS

In total, blood samples and questionnaires were collected from 9415 persons: 5745 (14.4%) in the NS (including the non-Western migrants), 1354 (19.8%) in LVC areas, 501 (6.9%) SAN, and 1815 (23.4%) in CN.

CONCLUSIONS

This study will give insight into protection of the population against infectious diseases included in the NIP. Research based on this large biobank will contribute to public health (policy) in NL and CN, e.g., regarding outbreak management and emerging pathogens. Further, we will be able to extend our knowledge on infectious diseases and its changing dynamics by linking serological data to results from additional materials collected, environmental- and pharmacological data.

Immunity against measles, mumps, rubella, varicella, diphtheria, tetanus, polio, hepatitis A and hepatitis B among adult asylum seekers in the Netherlands, 2016

Asylum seekers are a vulnerable population for contracting infectious diseases. Outbreaks occur among children and adults. In the Netherlands, asylum seeker children are offered vaccination according to the National Immunization Program. Little is known about protection against vaccine-preventable diseases (VPD) in adult asylum seekers. In this 2016 study, we assessed the immunity of adult asylum seekers against nine VPD to identify groups that might benefit from additional vaccinations. We invited asylum seekers from Syria, Iran, Iraq, Afghanistan, Eritrea and Ethiopia to participate in a serosurvey. Participants provided informed consent and a blood sample, and completed a questionnaire. We measured prevalence of protective antibodies to measles, mumps, rubella, varicella, diphtheria, tetanus, polio type 1-3 and hepatitis A and B, stratified them by country of origin and age groups. The median age of the 622 participants was 28 years (interquartile range: 23-35), 81% were male and 48% originated from Syria. Overall, seroprotection was 88% for measles (range between countries: 83-93%), 91% for mumps (81-95%), 94% for rubella (84-98%), 96% for varicella (92-98%), 82% for diphtheria (65-88%), 98% for tetanus (86-100%), 91% (88-94%) for polio type 1, 95% (90-98%) for polio type 2, 82% (76-86%) for polio type 3, 84% (54-100%) for hepatitis A and 27% for hepatitis B (anti-HBs; 8-42%). Our results indicate insufficient protection against certain VPD in some subgroups. For all countries except Eritrea, measles seroprotection was below the 95% threshold required for elimination. Measles seroprevalence was lowest among adults younger than 25 years. In comparison, seroprevalence in the Dutch general population was 96% in 2006/07. The results of this study can help prioritizing vaccination of susceptible subgroups of adult asylum seekers, in general and in outbreak situations.

Novel Intervention in the Aging Population: A Primary Meningococcal Vaccine Inducing Protective IgM Responses in Middle-Aged Adults

Introduction

Vaccine responses are often reduced in the elderly, leaving part of the elderly population vulnerable to infectious diseases. Timely vaccination may offer a solution for strengthening memory immunity before reaching old age, which classifies middle-aged persons as a target age group for vaccine interventions. However, knowledge regarding the immunogenicity of primary immunizations in middle-aged adults is lacking. We determined the immunogenicity of a primary meningococcal vaccine towards which no or (very) low pre-vaccination immunity exists in middle-aged adults (NTR4636).

Methods

A vaccine containing multiple meningococcal groups (tetravalent) conjugated to tetanus toxoid (MenACWY-TT) was administered to middle-aged adults (50–65 years of age, N = 204) in a phase IV single-center and open-label study. Blood samples were taken pre-, 7 days, 28 days, and 1 year post-vaccination. Functional antibody titers were measured with the serum bactericidal assay (SBA). Meningococcal- and tetanus-specific antibody responses were determined with a fluorescent bead-based multiplex immunoassay. A bi-exponential decay model was used to estimate long-term protection.

Results

In the majority of the participants, the meningococcal vaccine clearly induced naïve responses to meningococci W (MenW) and meningococci Y (MenY) as compared to a booster response to meningococci C (MenC). After 28 days, 94, 99, and 97% of the participants possessed a protective SBA titer for MenC, MenW, and MenY, respectively, which was maintained in 76, 94, and 86% 1 year post-vaccination. At this 1-year time point, significantly lower SBA titers were found in participants without a pre-vaccination SBA titer. Overall, protective antibody titers were predicted to persist after 10 years in 40–60% of the participants. The SBA titers correlated well with the meningococcal-specific IgM responses, especially for MenW and MenY. Interestingly, these IgM responses were negatively correlated with age.

Conclusion

Primary immunization with a tetravalent meningococcal vaccine was highly immunogenic in middle-aged adults, inducing protective antibody titers in the vast majority of the participants lasting for at least 1 year. The age-related decrease in highly functional IgM responses argues in favor of vaccination against de novo antigens before reaching old age and, hence, middle-aged persons are an age group of interest for future vaccine interventions to protect the aging population.

Non-protective immunity against tetanus in primiparous women and newborns at birth in rural and urban settings in Ibadan, Nigeria

INTRODUCTION

Nigeria remains among the few countries that are yet to achieve eradication of neonatal tetanus in the world despite the availability of an effective vaccine. This study investigated immunity against tetanus in primiparous mothers and neonates at birth, and identified associated factors.

METHODS

This cross-sectional study involved consecutive selection of 244 primiparous mother-neonate pairs (119 from rural areas, 125 from urban areas, 137 male neonates and 107 female neonates) delivered at primary healthcare facilities in Ibadan, Nigeria. Socio-demographic characteristics, obstetric history, immunisation and birthweight were obtained from mothers by interview. A validated immunochromatographic rapid diagnostic test kit was used to test for immunity against tetanus. Positive and negative results were interpreted as protective immunity against tetanus (PIaT) and non-protective immunity against tetanus (NPIaT), respectively. Data were analysed using descriptive statistics, Chi-square and logistic regression at p = 0.05.

RESULTS

The mean age of mothers was 27.9±3.4 years (range: 20-33) and median birthweight was 2700g (range: 1760-3300). Of the 244 mothers, 198 (81.1%) received at least two doses of tetanus toxoid injection during pregnancy and prevalence of NPIaT and PIaT was 28.7% and 71.3%, respectively. The prevalence of PIaT was significantly higher among mothers in urban areas (n= 96; 80.7%) than rural (n=78; 62.4%), p<0.001.The prevalence of NPIaT among neonates was 36.5% (n= 89). Predictors of NPIaT among neonates were residence in rural LGA (OR = 2.22; 95% CI = 1.23-3.99) and maternal tetanus immunisation <2 doses (OR = 11.68; 95% CI = 4.05-21.75).

CONCLUSION

Lack of protective immunity against tetanus among neonates of primiparous women in Ibadan is prevalent and a more conscientious enforcement of routine tetanus prevention practices is needed.

Vaccinations in migrants and refugees: a challenge for European health systems. A systematic review of current scientific evidence

The decline of immunization rates in countries of origin of migrants and refugees, along with risky conditions during the journey to Europe, may threaten migrants' health. We performed a systematic review of the scientific literature in order to assess the frequency of vaccine preventable diseases, and vaccination coverage among migrants and refugees in Europe. To this end, Medline and Cochrane databases were considered. After the screening and the selection process, 58 papers were included in the review. We focused on the following vaccine-preventable diseases: hepatitis B, measles, rubella, mumps, tetanus, poliomyelitis, pertussis, diphtheria, meningitis, and varicella. The results were presented as a qualitative synthesis. In summary, several studies highlighted that migrants and refugees have lower immunization rates compared to European-born individuals. Firstly, this is due to low vaccination coverage in the country of origin. Then, several problems may limit migrants' access to vaccination in Europe: (i) migrants are used to move around the continent, and many vaccines require multiple doses at regular times; (ii) information on the immunization status of migrants is often lacking; (iii) hosting countries face severe economic crises; (iv) migrants often refuse registration with medical authorities for fear of legal consequences and (v) the lack of coordination among public health authorities of neighboring countries may determine either duplications or lack of vaccine administration. Possible strategies to overcome these problems include tailoring immunization services on the specific needs of the target population, developing strong communication campaigns, developing vaccination registers, and promoting collaboration among public health authorities of European Countries.

Performance of a bedside test for tetanus immunity: results of a cross-sectional study among three EDs in the Netherlands in 2012-2013

INTRODUCTION

Despite sustained high vaccination coverage and a national guideline by the Health Council (HC-guideline) on tetanus postexposure prophylaxis (T-PEP), tetanus sporadically occurs in the Netherlands. This study aims to assess the added value of a bedside test for tetanus immunity (Tetanos Quick Stick (TQS); Ingen BioSciences Group, France), in the context of routine T-PEP in two adult cohorts: those born before introduction of tetanus toxoid vaccination in the National Immunization Programme (NIP) in 1957 (pre-NIP-cohort; n=196) and those born after (NIP-cohort; n=405).

METHODS

Adults included at the time of visiting one of three participating EDs received T-PEP as per routine recommendations. Subsequently, a nurse performed the TQS and filled in a questionnaire. We compared the indication for T-PEP based on TQS results with those based on the HC-guideline and with actually administration of T-PEP, stratified by cohort.

RESULTS

Among the pre-NIP and NIP-cohort, 16% and 9%, respectively, received T-PEP, while this was not indicated based on the HC-guideline. Furthermore, 8% and 7%, respectively, did not get T-PEP, although it was indicated by the guideline. Comparing the indication derived from the HC-guideline with TQS result found that 22% (pre-NIP-cohort) and 8% (NIP-cohort) were not eligible for T-PEP according to the HC-guideline but had a negative TQS. Conversely, 36% (pre-NIP-cohort) and 73% (NIP-cohort) were eligible for T-PEP according to the HC-guideline but had positive TQS, indicating sufficient tetanus protection.

CONCLUSION

Use of the TQS would allow better targeting of T-PEP. Furthermore, stricter adherence to the HC-guideline can prevent overimmunisation and decrease the risk of tetanus.

Factors contributing to the immunogenicity of meningococcal conjugate vaccines

Various glycoprotein conjugate vaccines have been developed for the prevention of invasive meningococcal disease, having significant advantages over pure polysaccharide vaccines. One of the most important features of the conjugate vaccines is the induction of a T-cell dependent immune response, which enables both the induction of immune memory and a booster response after repeated immunization. The nature of the carrier protein to which the polysaccharides are chemically linked, is often regarded as the main component of the vaccine in determining its immunogenicity. However, other factors can have a significant impact on the vaccine's profile. In this review, we explore the physico-chemical properties of meningococcal conjugate vaccines, which can significantly contribute to the vaccine's immunogenicity. We demonstrate that the carrier is not the sole determining factor of the vaccine's profile, but, moreover, that the conjugate vaccine's immunogenicity is the result of multiple physico-chemical structures and characteristics.

The use of tetanus post-exposure prophylaxis guidelines by general practitioners and emergency departments in the Netherlands: a cross-sectional questionnaire study

Background

The Dutch National Immunisation Programme includes six tetanus toxoid (TT) vaccinations and reaches a high rate of vaccination coverage. In the Netherlands, several guidelines related to tetanus post-exposure prophylaxis (T-PEP) are in place. In 2003, the Dutch Health Council (HC) reviewed the use of T-PEP. The aim of this study is to evaluate whether the HC recommendations have been implemented.

Methods

We asked 178 Dutch General Practitioner (GP) offices and 60 Emergency Departments (EDs) to participate in a cross-sectional questionnaire study and requested that participating facilities send in the T-PEP guidelines adopted by their practice. The differences, based on categories mentioned in the HC recommendations, between GPs and EDs and the type of T-PEP guidelines adopted were assessed.

Results

The response rates for the GPs and EDs were 38% (n = 67) and 70% (n = 42), respectively. 98% percent (n = 107) of the participants reported having T-PEP guidelines. Of the guidelines described in the survey responses, 28% (n = 23; EDs 41%, GPs 21%) were consistent with the HC-recommendations, 36% (n = 29; EDs 7%, GPs 52%) adhered to the guidelines of the College of GPs (CGP), which restricts the use of T-PEP to tetanus prone wounds but for these wounds is in line with the recommendations of the HC. The remaining 36% had adopted other guidelines, most of which can lead to over-prescription of T-PEP. Information on T-PEP was lacking in patients with higher risk vaccination histories.

Conclusion

Almost all participants have adopted T-PEP guidelines. Strict adherence to the HC recommendations is low. More than half of GPs have adopted the more restrictive CGP-guideline, which limits T-PEP to tetanus prone wounds.

Seroepidemiology of tetanus in Korean adults and adolescents in 2012

This seroepidemiologic study was performed to evaluate the immune status against tetanus in Korean adolescents and adults and to provide evidence to develop strategies for tetanus prevention. Between July 2012 and December 2012, serum samples were collected from adults and adolescents 11 years of age and older, and serum anti-tetanus IgG titers were determined using a commercial ELISA kit. Subjects were divided into six age groups: 11-20 years, 21-30 years, 31-40 years, 41-50 years, 51-60 years, and ≥61 years. The mean anti-tetanus IgG titers and tetanus seroprevalence of the age groups were compared. A total of 1193 adults and adolescents were enrolled. Mean anti-tetanus IgG titer and tetanus seroprevalence of all subjects were 1.20 ± 3.58 IU/mL and 56.4%, respectively. The mean anti-tetanus IgG titer decreased with an increase in age (p < 0.001). Tetanus seroprevalence increased from 92.0% in the 11-20 year age group to 95.7% in the 21-30 year age group, and then decreased with a further increase in age (p < 0.001). These results reflected an appropriate Td booster vaccine coverage at 11-12 years of age. However, the tetanus seroprevalence of adults older than 41 years was as low as the levels in previous studies: therefore, adults should be more encouraged to acquire decennial Td booster vaccinations recommended by the National Immunization Program.

Immunity against poliomyelitis in the Netherlands, assessed in 2006 to 2007: the importance of completing a vaccination series

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Seroprevalence of rubella antibodies in The Netherlands after 32 years of high vaccination coverage

Here we present rubella virus specific antibody levels in a large cross-sectional population-based serosurveillance study performed in The Netherlands in 2006/2007. In the nationwide sample, seroprevalence was high (95%). Higher levels of rubella specific antibodies were observed in the naturally infected cohorts compared with the vaccinated cohorts. After both vaccinations, the geometric mean concentration of rubella specific antibodies remained well above the protective level. However, antibody concentrations decreased faster after one than after two vaccinations. Infants too young to be vaccinated were a risk group in the nationwide sample. In the orthodox protestant group, individuals younger than 6 years of age were at risk for an infection with rubella, consistent with a small local outbreak that recently occurred at an orthodox protestant primary school. The general Dutch population is well protected against an infection with rubella virus. However, monitoring the rubella specific seroprevalence remains an important surveillance tool to assess possible groups at risk.

Tetanus in Italy 2001-2010: a continuing threat in older adults

Despite being a completely preventable disease, tetanus cases continue to occur in Italy and notification and hospitalization rates have been reported to be higher with respect to European and other industrialized countries. We examined statutory notification, hospitalization, mortality and seroprevalence data to describe tetanus epidemiology in Italy from 2001 to 2010. A total of 594 tetanus cases were notified, with an average annual incidence of 1.0/1,000,000 population. Most cases were unvaccinated or incompletely vaccinated. Eighty percent of cases occurred in subjects aged >64 years and a higher proportion of females with respect to males were reported in this age group. The annual number of hospital admissions was 1.4-1.7 times greater than the number of notifications in the same year. The mean annual number of reported deaths was 21. Seroprevalence data show progressively higher susceptibility levels with increasing age. Over 50% of persons aged 45-64 years and over two thirds of subjects ≥65 years had tetanus antibody levels <0.01 IU/ml. Results show that tetanus is a continuing problem in Italy and, as in other countries, most cases occur in older adults, especially elderly women. The observed differences in notification and hospitalization rates suggest underreporting by physicians. In recent years, Italy has accounted for most cases reported annually in the European Union (EU) but different case definitions are used. In Italy, a confirmed case is one that meets the clinical case definition while the EU case definition classifies confirmed cases as those with laboratory confirmation of disease. The incidence of clinical tetanus in Italy is ten-fold higher than in other industrialized countries, like Australia and Canada, likely due to higher susceptibility levels in Italy. In view of the low prevalence of tetanus antibodies in adults ≥45 years, strategies to improve vaccine uptake in this population group need to be implemented.

Immunogenicity and safety of a meningococcal serogroup A, C, Y and W glycoconjugate vaccine, ACWY-TT

A quadrivalent meningococcal serogroup A, C, W and Y conjugate vaccine (ACWY), utilising tetanus toxoid (TT) as its carrier protein (ACWY-TT; Nimenrix™, GlaxoSmithKline Vaccines, Rixensart, Belgium) has been demonstrated to be safe and immunogenic when administered to young children from 12 months of age, older children, adolescents, and adults. Administration of a single dose of ACWY-TT induces protective serum bactericidal antibodies against all four serogroups as well as good antibody persistence. Coadministration studies have demonstrated that ACWY-TT can be administered with diphtheria, tetanus, three-component acellular pertussis, hepatitis B, inactivated polio virus and Haemophilus influenzae type b conjugate vaccine (DTaP3-IPV-HBV/Hib, Infanrix™ hexa; GlaxoSmithKline Vaccines, Rixensart, Belgium); measles, mumps, rubella, varicella vaccine (Priorix-Tetra™; GlaxoSmithKline Vaccines, Rixensart, Belgium); 10-valent pneumococcal conjugate vaccine (Synflorix(®); GlaxoSmithKline Vaccines, Rixensart, Belgium); hepatitis A and B vaccine (Twinrix(®); GlaxoSmithKline Vaccines, Rixensart, Belgium); and seasonal influenza vaccine (Fluarix™; GlaxoSmithKline Vaccines, Rixensart, Belgium). Studies in young infants from 2 months of age have now commenced but immunisation with a single dose of ACWY-TT from 12 months of age is a safe and immunogenic option in the prevention of meningococcal disease.

Prevalence of susceptibility to tetanus and diphtheria in health care workers in Catalonia

A seroprevalence study of tetanus and diphtheria was carried out in a sample of 537 health care workers in Catalonia. The prevalence of protective antibodies against tetanus was 93.9% (95% confidence interval: 91.5-95.7). The prevalence of protective antibodies against diphtheria was 46.4% (95% confidence interval: 42.1-50.7). Tetanus protection should be improved in health care workers born before 1975. The immune status against diphtheria was poor, with less than half of people born before 1975 correctly immunized.

Immunity to tetanus and diphtheria in the UK in 2009

INTRODUCTION

This study aimed to estimate the immunity of the UK population to tetanus and diphtheria, including the potential impact of new glycoconjugatate vaccines, and the addition of diphtheria to the school leaver booster in 1994.

METHODS

Residual sera (n=2697) collected in England in 2009/10 were selected from 18 age groups and tested for tetanus and diphtheria antibody. Results were standardised by testing a panel of sera (n=150) to enable comparison with a previously (1996) published serosurvey. Data were then standardised to the UK population.

RESULTS

In 2009, 83% of the UK population were protected (≥0.1 IU/mL) against tetanus compared to 76% in 1996 (p=0.079), and 75% had at least basic protection against diphtheria (≥0.01 IU/mL) in 2009 compared to 60% in 1996 (p<0.001). Higher antibody levels were observed in those aged 1-3 years in 2009 compared to 1996 for both tetanus and diphtheria. Higher diphtheria immunity was observed in those aged 16-34 years in 2009 compared to 1996 (geometric mean concentration [GMC] 0.15 IU/mL vs. 0.03 IU/mL, p<0.001). Age groups with the largest proportion of susceptible individuals to both tetanus and diphtheria in 2009 were <1 year old (>29% susceptible), 45-69 years (>20% susceptible) and 70+ years (>32% susceptible). Low immunity was observed in those aged 10-11 years (>19% susceptible), between the scheduled preschool and school leaver booster administration.

DISCUSSION

The current schedule appears to induce protective levels; increases in the proportions protected/GMCs were observed for the ages receiving vaccinations according to UK policy. Glycoconjugate vaccines appear to have increased immunity, in particular for diphtheria, in preschool age groups. Diphtheria immunity in teenagers and young adults has increased as a result of the addition of diphtheria to the school leaver booster. However, currently older adults remain susceptible, without any further opportunities for immunisations planned according to the present schedule.

Differences in persistence of measles, mumps, rubella, diphtheria and tetanus antibodies between children with rheumatic disease and healthy controls: a retrospective cross-sectional study

OBJECTIVES

To compare the persistence of measles, mumps, rubella, diphtheria and tetanus antibodies between patients with juvenile idiopathic arthritis (JIA) and healthy controls.

METHODS

Measles, mumps, rubella (MMR) and diphtheria-tetanus toxoid (DT)-specific immunoglobulin G antibody concentrations were compared between 400 patients with JIA and 2176 healthy controls aged 1-19 years. Stored patient samples from the period 1997-2006 were obtained from one Dutch centre for paediatric rheumatology. Healthy control samples had been evaluated previously in a nationwide cohort. Participants had been vaccinated according to the Dutch immunisation programme. Antibody concentrations were measured by ELISA (MMR) or multiplex immunoassay (DT).

RESULTS

Corrected for age and the number of vaccinations, lower vaccine-specific geometric mean antibody concentrations (GMC) were found in patients with JIA against mumps, rubella, diphtheria and tetanus (p≤0.001). Measles-specific GMC were higher (p<0.001) compared with healthy controls. The prevalence of protective antibody concentrations was significantly lower in patients for mumps (OR 0.4; 95% CI 0.3 to 0.6), rubella (OR 0.4; 0.3 to 0.7), diphtheria (OR 0.1; 0.06 to 0.2) and tetanus (OR 0.1; 0.05 to 0.3). Seroprotection rates against measles did not differ between patients and healthy controls (OR 1.4; 0.8 to 2.5). Methotrexate and glucocorticosteroid use did not affect pathogen-specific GMC or seroprotection rates.

CONCLUSIONS

Patients with JIA had lower antibody concentrations and seroprotection rates than healthy controls against mumps, rubella, diphtheria and tetanus, but not measles. In these patients, regular assessment of antibody concentrations and further research on responses to other (booster) vaccines are warranted.

Impact of treatment reduction for childhood acute lymphoblastic leukemia on serum immunoglobulins and antibodies against vaccine-preventable diseases

BACKGROUND

The consequences of current intensive chemotherapy for childhood acute lymphoblastic leukemia (ALL) for immune defense are a matter of concern. The purpose of this study was to examine the effect of reduced compared with intensive (conventional) ALL chemotherapy on serum immunoglobulin levels and specific antibody concentrations against vaccine-preventable diseases.

PROCEDURE

Patients treated according to Dutch Childhood Oncology Group ALL 10 protocol were stratified by minimal residual disease to receive reduced (standard risk; SR) or intensive (medium risk; MR) intensification/maintenance treatment. Between November 2004 and July 2009 we compared serum immunoglobulins of 110 patients and specific antibodies against diphtheria toxin, tetanus toxin, and Bordetella pertussis antigens of 41 patients of SR and MR groups during chemotherapy.

RESULTS

Immunoglobulin levels showed significantly different patterns between the SR and MR groups. In the MR group IgG, IgA, and IgM levels decreased towards the end of intensive treatment; in the SR group IgG levels increased while IgA and IgM stabilized. In both groups IgM and IgG levels were most affected. Specific antibody levels against vaccine-preventable diseases decreased in both groups, but more profound in MR group.

CONCLUSIONS

Although reduced chemotherapy is beneficial for immunoglobulin level recovery and might prevent susceptibility for infections, specific antibodies remain decreased.

Improved specificity of a multiplex immunoassay for quantitation of anti-diphtheria toxin antibodies with the use of diphtheria toxoid

A nonspecific binding of antibodies to diphtheria toxin, especially in adult serum samples, was observed in our diphtheria-tetanus-pertussis multiplex immunoassay (DTaP4 MIA). This can be significantly reduced by the use of diphtheria toxoid, achieving a good correlation with the Vero cell neutralization test and the toxin binding inhibition assay.