Safety and immunogenicity of coadministering a combined meningococcal serogroup C and Haemophilus influenzae type b conjugate vaccine with 7-valent pneumococcal conjugate vaccine and measles, mumps, and rubella vaccine at 12 months of age

Reassurance of population immunity to diphtheria in England: Results from a 2021 national serosurvey

BACKGROUND

Diphtheria is rare in England because of an effective national immunisation schedule that includes 5 doses of a diphtheria-containing vaccine at 2, 3, 4 months, preschool and adolescent boosters. However, in recent years there has been a notable increase in cases due to Corynebacterium ulcerans among older adults and evidence of endemic transmission of C. diphtheriae (normally associated with travel to endemic countries). We aimed to update 2009 estimates of diphtheria immunity considering the evolving epidemiology.

METHODS

Residual sera collected from diagnostic laboratories and general practitioners in England in 2021 were randomly selected and tested for diphtheria antibody, to estimate proportions protected per age group. Diphtheria antibody levels were defined as susceptible (<0.01 IU/mL), basic protection (0.01-0.099 IU/mL) and full protection (≥0.1 IU/mL). Immunity estimates were standardised to the England population and compared to 2009.

RESULTS

Based on 3,745 residual sera tested, 89% (95%CI: 87%-90%) of the 2021 England population had at least basic diphtheria protection (vs. 90% [88%-92%] in 2009) and 50% (48%-52%) full protection (vs. 41% [38%-44%]). Higher antibody levels were observed in those aged 1 and under, 10-11, 12-15, 25-34 and 35-44 years compared to 2009. The largest proportion susceptible were observed in those aged 70+, 26% (21%-31%) vs 12% (7%-18%) in 2009.

CONCLUSIONS

Basic diphtheria protection is comparable between 2021 and 2009. The increase in immunity in working age adults is likely due to the school leaver booster introduced in 1994. The current vaccination schedule is maintaining sufficient population immunity. However, we recommend clinicians remain vigilant to severe diphtheria outcomes in older adults, because of their observed susceptibility.

Safety of routine childhood vaccine coadministration versus separate vaccination

INTRODUCTION

As new vaccines are developed more vaccine coadministrations vaccines are being offered to make delivery more practical for health systems and patients. We compared the safety of coadministered vaccines with separate vaccination for 20 coadministrations by considering nine types of adverse events following immunisation (AEFI).

METHODS

Real-life immunisation and adverse event data for this observational cohort study were extracted from the Oxford-Royal College of General Practitioners Research and Surveillance Centre for children registered in the database between 2008 and 2018. We applied the self-controlled case series method to calculate relative incidence ratios (RIR) for AEFI. These RIRs compare the RI of AEFI following coadministration with the RI following separate administration of the same vaccines.

RESULTS

We assessed 3 518 047 adverse events and included 5 993 290 vaccine doses given to 958 591 children. 17% of AEFI occurred less and 11% more frequently following coadministration than would have been expected based on the RIs following separate vaccinations, while there was no significant difference for 72% of AEFI. We found amplifying interaction effects for AEFI after five coadministrations comprising three vaccines: for fever (RIR 1.93 (95% CI 1.63 to 2.29)), rash (RIR 1.49 (95% CI 1.29 to 1.74)), gastrointestinal events (RIR 1.31 (95% CI 1.14 to 1.49)) and respiratory events (RIR 1.27 (1.17-1.38)) following DTaP/IPV/Hib+MenC+ PCV; gastrointestinal events (RIR 1.65 (95% CI 1.35 to 2.02)) following DTaP/IPV/Hib+MenC+ RV; fever (RIR 1.44 (95% CI 1.09 to 1.90)) and respiratory events (RIR 1.40 (95% CI 1.25 to 1.57)) following DTaP/IPV/Hib+PCV+ RV; gastrointestinal (RIR 1.48 (95% CI 1.20 to 1.82)) and respiratory events (RIR 1.43 (95% CI 1.26 to 1.63)) following MMR+Hib/MenC+PCV; gastrointestinal events (RIR 1.68 (95% CI 1.07 to 2.64)) and general symptoms (RIR 11.83 (95% CI 1.28 to 109.01)) following MMR+MenC+PCV. Coadministration of MMR+PCV led to more fever (RIR 1.91 (95% CI 1.83 to 1.99)), neurological events (RIR 2.04 (95% CI 1.67 to 2.49)) and rash (RIR 1.06 (95% CI 1.01 to 1.11)) compared with separate administration, DTaP/IPV/Hib+MMR to more musculoskeletal events (RIR 3.56 (95% CI 1.21 to 10.50)) and MMR+MenC to more fever (RIR 1.58 (95% CI 1.37 to 1.82)). There was no indication that unscheduled coadministrations are less safe than scheduled coadministrations.

CONCLUSION

Real-life RIRs of AEFI justify coadministering routine childhood vaccines according to the immunisation schedule. Further research into the severity of AEFI following coadministration is required for a complete understanding of the burden of these AEFI.

Vaccine safety issues at the turn of the 21st century

Global gains in vaccination coverage during the early 21st century have been threatened by the emergence of antivaccination groups that have questioned the effectiveness of vaccines to generate public distrust of vaccines and immunisation programmes. This manuscript summarises six key topics that have been at the centre of global discussions on vaccine safety during the early 21st century: thiomersal in multi-dose non-live vaccines, aluminium adjuvants used with several non-live vaccines, autism and auto-immune conditions as possible consequences of vaccination, a risk of immune overload with increasing numbers of vaccinations, and detrimental non-specific effects (NSEs) of vaccination. For each topic, we describe the hypothesis behind the public concern, the evidence reviewed by the WHO’s Global Advisory Committee for Vaccine Safety (GACVS) during 1999–2019, and any significant new data that has emerged since GACVS conclusions were made. Although the scientific evidence on these issues overwhelmingly supports the safety of vaccines, communication messages to caregivers and providers need to condense and convey scientific information in an appropriate way to address concerns contributing to vaccine distrust. In addition, there is need for further studies specifically designed to address both positive and negative NSE of vaccination. The role of GACVS will be increasingly important in evaluating the evidence and engaging the global community in promoting and assuring the safety of vaccines in the decades to come as we move into an era in which we use new vaccination platforms, antigens and formulations.

Vaccines Safety in Children and in General Population: A Pharmacovigilance Study on Adverse Events Following Anti-Infective Vaccination in Italy

Background: The concern for adverse events following immunization (AEFI) and anti-vaccination movements that lacked scientific evidence-based supports may reduce vaccine uptake in the general population. Thus, the aims of the present study were to characterize AEFI in general population (all age groups), in terms of frequency, preventability, and seriousness and to define predictors of their seriousness in children.

Methods: A retrospective study was performed on suspected AEFI reports for children and adults who received any form of vaccinations, collected in Tuscany, Italy, between 1 January and 31 December 2017. Patients’ characteristics, suspected vaccines, and AEFI description were collected. Causality and preventability were assessed using WHO and Schumock and Thornton algorithms, respectively. Logistic regression was used to estimate the reporting odds ratios of potential predictors of AEFI seriousness in children.

Results: A total of 223 suspected AEFI reports were collected, and the majority of them were defined as non-serious (76.7%). Reports were mostly related to one vaccine, and to a median of two to five strains/toxoids. The total number of simultaneously administered strains/toxoids and the presence of allergens did not correlate with AEFI seriousness. Considering vaccines with a high number of administered doses (≥60,000 doses), the rates estimated for serious AEFI reports were always very low, ranging between 0.01 and 0.2/1,000 doses. Twenty-four vaccines (8,993 doses) were not related to any AEFI.

Conclusion: Results of present study showed that AEFI were very rare; the vast majority of them was non-serious and, despite the claims of anti-vaccination movements, the simultaneous administration of vaccines was safe and did not influence the risk of reporting a serious AEFI, particularly in children.

Tetanus-diphtheria vaccination in adults: the long-term persistence of antibodies is not dependent on polyclonal B-cell activation and the defective response to diphtheria toxoid re-vaccination is associated to HLADRB1∗01

Cellular and humoral immune responses to tetanus-diphtheria vaccine (Td) were assessed in human leukocyte antigen (HLA)-typed Italian military personnel who received multiple concomitant vaccines. Td-specific antibodies and T-lymphocytes were measured in individuals with one (group-1) and more than one (group-2) Td boosters. A third group (group-3), who received several vaccines, but not Td, was studied to verify the hypothesis of the polyclonal B-cell activation as mechanism for antibody persistence. The antibody response to Td toxoids was higher in group-1, who showed lower baseline antibody levels, than in group-2 subjects. The antibody response to tetanus was higher than to diphtheria toxoid in both groups. No correlation between antibody and cellular response, and no interference in the response to Td by co-administration of different vaccines were observed. HLA-DRB1∗01 allele was detected at significant higher frequency in subjects unable to double the baseline anti-diphtheria antibody levels after the vaccination. Anti-tetanus and diphtheria antibodies half-lives were assessed and the long-lasting persistence above the threshold for protection (0.1 IU/ml) was estimated in over 65 and 20 years, respectively. No significant increase of anti-diphtheria antibodies was observed in consequence of polyclonal B-cell activation. This study emphasizes the duration of Td vaccination-induced seroprotection, suggesting that re-vaccination should probably be performed at intervals longer than 10 years. No reciprocal interference by concomitantly administered vaccines has been observed. HLA-DRB1∗01 allele was significantly associated with anti-diphtheria defective response. Finally, this study does not confirm that anti-diphtheria antibody levels are maintained by polyclonal B-cell activation. Clinical trial registry: The study was registered with NCT01807780.

Effect of Tdap upon antibody response to meningococcal polysaccharide when administered before, with or after the quadrivalent meningococcal TT-conjugate vaccine (coadministered with the 13-valent pneumococcal CRM197-conjugate vaccine) in adult Hajj pilgrims: A randomised controlled trial

Hajj pilgrims are susceptible to several serious infections and are required to receive multiple vaccinations. Polysaccharide-protein conjugate vaccines contain carrier proteins such as tetanus toxoid (TT), diphtheria toxoid or a mutant of diphtheria toxoid (CRM197). These carrier proteins may interact with other conjugate or combination vaccines containing tetanus or diphtheria on concurrent or sequential administration. We examined the immune interaction of separate and concomitant administration of a tetanus/diphtheria/acellular pertussis (Tdap) vaccine with a TT-conjugated quadrivalent meningococcal vaccine (MCV4) (coadministered with 13-valent pneumococcal CRM197-conjugate vaccine [PCV13]) in adult Australian pilgrims before attending Hajj in 2015. We randomly assigned each participant to one of three vaccination schedules. Group 1 received Tdap 3-4 weeks before receiving MCV4 coadministered with PCV13. Group 2 received all three vaccines concomitantly. Group 3 received MCV4 and PCV13 3-4 weeks before Tdap. Blood samples were collected at baseline, at each vaccination visit and 3-4 weeks after vaccination and tested for response to meningococcal serogroups C, W and Y using a serum bactericidal antibody (rSBA) assay with baby rabbit complement, and to diphtheria and tetanus toxoid, measuring IgG antibodies by ELISA. Participants completed symptom diaries after each vaccination. A total of 166 participants aged 18-64 (median 42) years were recruited, of whom 160 completed the study. Compared to the other groups, Group 1 (given Tdap first) had significantly lower proportion of subjects achieving a ≥4-fold rise in rSBA for serogroup W. No difference was detected across the three groups in achieving protection threshold (rSBA ≥8 post vaccination) or SBA geometric mean titre (GMT) post vaccination. Group 3, which was given MCV4/PCV13 first, had high levels of antibody against diphtheria and tetanus than the other groups, when tested prior to receipt of Tdap; Only the anti-tetanus responses remained significantly higher after Tdap administration. No serious adverse events were reported. In conclusion, when multiple vaccination is required for Hajj pilgrims, administering Tdap concurrently with MCV4/PCV13 produces adequate immune responses, and avoids meningococcal immune interference, in the convenience of a single consultation. However, giving Tdap 3-4 weeks after MCV4/PCV13 has the advantage of an enhanced tetanus toxoid response. The trial is Trials Registry (ANZCTR): ACTRN12613000536763.

Differences by sex in IgG levels following infant and childhood vaccinations: An individual participant data meta-analysis of vaccination studies

BACKGROUND

If immune responses to vaccination differ between males and females, sex-specific vaccination schedules may be indicated. We systematically reanalysed childhood vaccination studies conducted in The Netherlands for sex-differences in IgG-responses. To assess the impact of potential sex-differences in IgG-responses, we explored sex-differences in vaccine failure/effectiveness and reactogenicity.

METHODS

Six studies with IgG-measurements for 1577 children following infant pneumococcal (PCV7/PCV10/PCV13) and/or DTaP-IPV-Hib(-HepB) vaccinations, or the pre-school DTaP-IPV booster were included. We performed one-stage individual participant data meta-analyses per time-point of the effect of sex on IgG levels against pneumococcal serotypes, diphtheria toxoid, tetanus toxoid, pertussis Ptx/FHA/Prn and Hib-PRP using linear mixed models. Using existing study data, we compared reactogenicity after PCV7/PCV10 and DTaP-IPV-Hib(-HepB) vaccination in girls and boys. Vaccine failure/effectiveness was compared between girls and boys for invasive pneumococcal disease (IPD), invasive Hib disease and pertussis using notification data.

RESULTS

For pneumococcal vaccination, the geometric mean concentration ratio of IgG levels in girls versus boys pooled across serotypes was 1.15 (95%CI 0.91-1.45) 1 month following the primary series, 1.16 (1.02-1.32) at age 8 months, 1.12 (1.02-1.23) pre-booster (age 11 months) and 0.99 (0.89-1.10) post-booster (age 12 months). Diphtheria toxoid, tetanus toxoid, pertussis Ptx/FHA/Prn and Hib-PRP IgG levels did not differ between girls and boys, except for Hib post-booster (1.24; 95%CI 1.01-1.52) and tetanus before pre-school booster (0.71; 0.53-0.95). We found no difference between boys and girls in reactogenicity at age 4 or 11 months or in vaccine failure/effectiveness for IPD, invasive Hib disease or pertussis.

CONCLUSION

For most vaccine antigens investigated, there were no consistent differences in vaccine-induced IgG levels. Vaccine-induced pneumococcal IgG levels were slightly higher in girls, but only between the primary series and the 11-month booster. These results, along with similar reactogenicity and vaccine failure/effectiveness, support the uniform infant vaccination schedule in the Dutch national immunisation programme.

Interactions of conjugate vaccines and co-administered vaccines

Conjugate vaccines play an important role in the prevention of infectious diseases such as those caused by the bacteria Haemophilus influenzae (Hi) type b (Hib), Neisseria meningitidis, and Streptococcus pneumoniae. Vaccines developed against these 3 pathogens utilize 3 main carrier proteins, non-toxic mutant of diphtheria toxin (CRM197), diphtheria toxoid (DT) and tetanus toxoid (TT). Current pediatric immunisation schedules include the administration of several vaccines simultaneously, therefore increasing the potential for immune interference (both positively and negatively) to the antigens administered. Knowledge of vaccine interactions is principally derived from clinical trials, these are reviewed here to explore immune interference which may result of from carrier-specific T-cell helper interactions, bystander interference and carrier induced epitopic suppression.

Effect of Tdap when administered before, with or after the 13-valent pneumococcal conjugate vaccine (coadministered with the quadrivalent meningococcal conjugate vaccine) in adults: A randomised controlled trial

Sequential or co-administration of vaccines has potential to alter the immune response to any of the antigens. Existing literature suggests that prior immunisation of tetanus/diphtheria-containing vaccines can either enhance or suppress immune response to conjugate pneumococcal or meningococcal vaccines. We examined this interaction among adult Australian travellers before attending the Hajj pilgrimage 2014. We also investigated tolerability of these vaccines separately and concomitantly. We randomly assigned each participant to one of three vaccination schedules. Group A received adult tetanus, diphtheria and acellular pertussis vaccine (Tdap) 3-4weeks before receiving CRM197-conjugated 13-valent pneumococcal vaccine (PCV13) and CRM197-conjugated quadrivalent meningococcal vaccine (MCV4). Group B received all three vaccines on one day. Group C received PCV13 and MCV4 3-4weeks before Tdap. Blood samples collected at baseline, each vaccination visit and 3-4weeks after vaccination were tested using the pneumococcal opsonophagocytic assay (OPA) and by ELISA for diphtheria and tetanus antibodies. Funding for meningococcal serology was not available. Participants completed symptom diaries after each vaccination. A total of 111 participants aged 18-64 (median 40) years were recruited. No statistically significant difference was detected across the three groups in achieving OPA titre ⩾1:8 post vaccination. However, compared to other groups, Group A had a statistically significant lower number of subjects achieving ⩾4-fold rise in serotype 3, and also significantly lower geometric mean titres (GMTs) to six (of 13) pneumococcal serotypes (3, 5, 18C, 4, 19A and 9V). Group C (given prior PCV13 and MVC4) had statistically significant higher pre-Tdap geometric mean concentration (GMC) of anti-diphtheria IgG; however, there was no difference across the three groups following Tdap. Anti-tetanus IgG GMCs were similar across the groups before and after Tdap. No serious adverse events were reported. In conclusion, Tdap vaccination 3-4weeks before concomitant administration of PCV13 and MCV4 significantly reduced the antibody response to six of the 13 pneumococcal serotypes in adults. The trial is registered at the Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12613000536763.

Immune response to 13-valent pneumococcal conjugate vaccine with a reduced dosing schedule

BACKGROUND

The 7-valent pneumococcal conjugate vaccine (PCV7) has demonstrated effectiveness against pneumococcal illnesses when administered as 3 infant doses plus a toddler dose (3+1 schedule) or as an abbreviated schedule of 2 infant doses plus a toddler dose (2+1 schedule). The 13-valent pneumococcal conjugate vaccine (PCV13) is approved and World Health Organization-prequalified for administration in a 2+1 schedule when used as part of routine immunization programs.

OBJECTIVE

To summarize immunologic responses elicited by PCV13 administered in a 2+1 schedule and following 2 doses in a 3+1 schedule.

METHODS

Studies were double-blind, randomized, active-controlled, multicenter studies except the Mexico study (open-label, single-arm). In 2+1 studies, PCV13 was administered at 2, 4, and 12 (UK) or 3, 5, and 11 (Italy) months. In 3+1 studies (Spain and Mexico), assessment was made postdose 2 of the primary series (2, 4, and 6 months). The primary immunogenicity endpoint was the proportion of participants achieving serotype-specific antipolysaccharide immunoglobulin (Ig)G concentrations ≥ 0.35μg/mL (i.e., responders) 1 month postdose 2. Pneumococcal IgG geometric mean concentrations (GMCs), opsonophagocytic activity (OPA), and concomitant vaccine responses were assessed.

RESULTS

PCV13 and PCV7 elicited comparable immune responses for the 7 common serotypes after 2 infant doses. The proportion of PCV13 responders postdose 2 was >85% for most of the 7 common and 6 additional serotypes, except common serotypes 6B (27.9-81.4%) and 23F (55.8-77.5%) and additional serotypes 3 (73.8-96.9%) and 6A (79.2-94.4%). Serotypes 6B and 23F elicited lower IgG GMCs postdose 2 compared with other serotypes; all serotypes demonstrated boosting posttoddler dose. All serotypes demonstrated functional activity; >95% of participants achieved OPA levels ≥ 1:8 postdose 2. Concomitant vaccine responses were similar between PCV13 and PCV7 groups.

CONCLUSION

Immune responses elicited by PCV13 following 2 infant doses support transition from PCV7 to PCV13 in countries using a 2+1 schedule.

Pneumococcal 13-valent conjugate vaccine for the prevention of invasive pneumococcal disease in children and adults

Pneumococcal disease remains a global problem despite the availability of effective conjugate vaccines. The 13-valent pneumococcal conjugate vaccine (PCV13) extends the valency of PCV7 by including six additional serotypes highly associated with invasive pneumococcal disease (IPD). Comparisons between PCV13 and PCV7 or the pneumococcal polysaccharide vaccine have established noninferiority of PCV13 for both safety and immunogenicity profiles for use in children and adults, respectively. At the end of 2011, PCV13 had been approved and launched in 104 countries worldwide, with 54 including the vaccine in their pediatric national immunization program. Surveillance data from early adopters of PCV13 has indicated reductions are occurring in both overall IPD and IPD caused by the six non-PCV7 serotypes; early reports of serotype replacement in carriage are also emerging. While serotype replacement for PCV7 was observed to varying degrees for both carriage and disease, the extent to which this will occur for PCV13 is yet to be determined.

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.

Immunogenicity of a single dose of meningococcal group C conjugate vaccine given at 3 months of age to healthy infants in the United kingdom

BACKGROUND

From 1999, in the United Kingdom, meningococcal C conjugate (MCC) vaccines from 3 manufacturers were introduced to the infant immunization schedule at 2, 3 and 4 months of age. In 2006, the schedule was refined to a 2-dose primary schedule at 3 and 4 months of age, with a combined MCC/Haemophilus influenzae type b (MCC/Hib-TT) booster at 12 months of age. Recent data have demonstrated that 2 of the 3 MCC vaccines showed potential for use as a single priming dose in infancy.

METHODS

A randomized trial was undertaken with 2 MCC vaccines; one using tetanus toxoid carrier protein (MCC-TT) and one using CRM197 carrier protein (MCC-CRM197). Infants were immunized with MCC at 3 months of age followed by an MCC/Hib-TT booster at 12 months of age.

RESULTS

The serum bactericidal antibody geometric mean titers 1 month after a single dose of MCC-TT or MCC-CRM 197 were 223.3 (95% confidence interval [CI]: 162.9-306.1) and 95.8 (95% CI: 66.4-138.2) with 100% and 95.5% of infants having serum bactericidal antibody titers ≥ 8, respectively. Before boosting, antibody titers had declined, and 1 month after the MCC/Hib-TT booster, serum bactericidal antibody geometric mean titers rose to 2251.0 (95% CI: 1535.3-3300.3) and 355.9 (95% CI: 235.4-538.1) for children primed with MCC-TT and MCC-CRM 197, respectively.

CONCLUSIONS

In conclusion, a single priming dose of either MCC-TT or MCC-CRM197 administered at 3 months of age can be used together with the Hib/MCC-TT booster in the second year of life.

Evaluation of haemophilus influenzae type b vaccine for routine immunization in Nepali infants

BACKGROUND

Haemophilus influenzae type b (Hib) carriage and disease studies in Nepali children suggest a significant burden of infection. Hib conjugate vaccines (HibCV) do not have uniform immunogenicity between populations. We determined the immunogenicity of HibCV in Nepali infants, before its introduction into the routine immunization schedule.

METHODS

Ninety infants recruited at Patan Hospital, Kathmandu, received 3 doses of the HibCV with routine immunizations (diphtheria, tetanus, whole cell pertussis-hepatitis B vaccine + oral polio vaccine) at 6, 10 and 14 weeks of age, and a HibCV booster at 52 weeks. Anti-polyribosylribitol phosphate (PRP) concentrations were measured at 18, 52 and 56 weeks, and the antibody persistence at 52 weeks was compared with antibody values in unimmunized controls (n = 30).

RESULTS

After 3 doses of primary immunizations, at 18 weeks of age (n = 74), all infants had anti-PRP concentrations above the accepted thresholds for short- and long-term protection (0.15 and 1.0 µg/mL, respectively). At 1 year of age, before administration of the booster of HibCV, the anti-PRP geometric mean antibody concentration was 2.76 µg/mL (confidence interval: 1.88-4.07) in sera from the immunized children compared with 0.11 µg/mL (95% confidence interval: 0.08-0.17) in the nonimmunized control group (n = 30). Twenty-seven percent (20/74) of participants, however, had anti-PRP concentrations <1.0 µg/mL. Four weeks after the booster dose of HibCV, 98.5% of infants had anti-PRP concentrations above 1.0 µg/mL.

CONCLUSION

Immunization with HibCV given as part of the Expanded Program on Immunization schedule in Nepal elicits robust antibody responses. Though the antibody wanes during the first year of life, most 1-year-old infants remain protected and respond robustly to a booster dose of the vaccine.

Mechanisms of aluminum adjuvant toxicity and autoimmunity in pediatric populations

Immune challenges during early development, including those vaccine-induced, can lead to permanent detrimental alterations of the brain and immune function. Experimental evidence also shows that simultaneous administration of as little as two to three immune adjuvants can overcome genetic resistance to autoimmunity. In some developed countries, by the time children are 4 to 6 years old, they will have received a total of 126 antigenic compounds along with high amounts of aluminum (Al) adjuvants through routine vaccinations. According to the US Food and Drug Administration, safety assessments for vaccines have often not included appropriate toxicity studies because vaccines have not been viewed as inherently toxic. Taken together, these observations raise plausible concerns about the overall safety of current childhood vaccination programs. When assessing adjuvant toxicity in children, several key points ought to be considered: (i) infants and children should not be viewed as “small adults” with regard to toxicological risk as their unique physiology makes them much more vulnerable to toxic insults; (ii) in adult humans Al vaccine adjuvants have been linked to a variety of serious autoimmune and inflammatory conditions (i.e., “ASIA”), yet children are regularly exposed to much higher amounts of Al from vaccines than adults; (iii) it is often assumed that peripheral immune responses do not affect brain function. However, it is now clearly established that there is a bidirectional neuro-immune cross-talk that plays crucial roles in immunoregulation as well as brain function. In turn, perturbations of the neuro-immune axis have been demonstrated in many autoimmune diseases encompassed in “ASIA” and are thought to be driven by a hyperactive immune response; and (iv) the same components of the neuro-immune axis that play key roles in brain development and immune function are heavily targeted by Al adjuvants. In summary, research evidence shows that increasing concerns about current vaccination practices may indeed be warranted. Because children may be most at risk of vaccine-induced complications, a rigorous evaluation of the vaccine-related adverse health impacts in the pediatric population is urgently needed.

Do aluminum vaccine adjuvants contribute to the rising prevalence of autism?

Autism spectrum disorders (ASD) are serious multisystem developmental disorders and an urgent global public health concern. Dysfunctional immunity and impaired brain function are core deficits in ASD. Aluminum (Al), the most commonly used vaccine adjuvant, is a demonstrated neurotoxin and a strong immune stimulator. Hence, adjuvant Al has the potential to induce neuroimmune disorders. When assessing adjuvant toxicity in children, two key points ought to be considered: (i) children should not be viewed as "small adults" as their unique physiology makes them much more vulnerable to toxic insults; and (ii) if exposure to Al from only few vaccines can lead to cognitive impairment and autoimmunity in adults, is it unreasonable to question whether the current pediatric schedules, often containing 18 Al adjuvanted vaccines, are safe for children? By applying Hill's criteria for establishing causality between exposure and outcome we investigated whether exposure to Al from vaccines could be contributing to the rise in ASD prevalence in the Western world. Our results show that: (i) children from countries with the highest ASD prevalence appear to have the highest exposure to Al from vaccines; (ii) the increase in exposure to Al adjuvants significantly correlates with the increase in ASD prevalence in the United States observed over the last two decades (Pearson r=0.92, p<0.0001); and (iii) a significant correlation exists between the amounts of Al administered to preschool children and the current prevalence of ASD in seven Western countries, particularly at 3-4 months of age (Pearson r=0.89-0.94, p=0.0018-0.0248). The application of the Hill's criteria to these data indicates that the correlation between Al in vaccines and ASD may be causal. Because children represent a fraction of the population most at risk for complications following exposure to Al, a more rigorous evaluation of Al adjuvant safety seems warranted.