Calcium phosphate: a substitute for aluminum adjuvants?

INTRODUCTION: Calcium phosphate was used as an adjuvant in France in diphtheria, tetanus, pertussis and poliomyelitis vaccines. It was later completely substituted by alum salts in the late 80's, but it still remains as an approved adjuvant for the World Health Organization for human vaccination. Area covered: Thus, calcium phosphate is now considered as one of the substances that could replace alum salts in vaccines. The aim of this paper is to draw a review of existing data on calcium phosphate as an adjuvant in order to bring out the strengths and weaknesses for its use on a large scale. Expert commentary: Calcium phosphate is a compound naturally present in the organism, safe and already used in human vaccination. Beyond comparisons with the other adjuvants, calcium phosphate represents a good candidate to replace or to complete alum salts as a vaccine adjuvant.

The potential of adjuvants to improve immune responses against TdaP vaccines: A preclinical evaluation of MF59 and monophosphoryl lipid A.

The successful approach of combining diphtheria, tetanus and pertussis antigens into a single vaccine has become a cornerstone of immunization programs. Yet, even if vaccination coverage is high, a resurgence of pertussis has been reported in many countries suggesting current vaccines may not provide adequate protection. To induce better tailored and more durable immune responses against pertussis vaccines different approaches have been proposed, including the use of novel adjuvants. Licensed aP vaccines contain aluminum salts, which mainly stimulate humoral immune responses and might not be ideal for protecting against Bordetella pertussis infection. Adjuvants inducing more balanced T-helper profiles or even Th1-prone responses might be more adequate. In this study, two adjuvants already approved for human use have been tested: MF59 emulsion and the combination of aluminum hydroxide with the Toll-Like Receptor 4 agonist MPLA. Adjuvanticity was evaluated in a mouse model using a TdaP vaccine containing three B. pertussis antigens: genetically detoxified pertussis toxin (PT-9K/129G), filamentous hemagglutinin (FHA) and pertactin (PRN) The physico-chemical compatibility of TdaP antigens with the proposed adjuvants, together with a quicker onset and changed quality of the antibody responses, fully supports the replacement of aluminum salts with a new adjuvant to enhance aP vaccines immunogenicity.

Decennial administration in young adults of a reduced-antigen content diphtheria, tetanus, acellular pertussis vaccine containing two different concentrations of aluminium.

BACKGROUND: Regular booster vaccination might be necessary throughout life to protect against pertussis infection. Nevertheless the duration of protection after booster vaccination remains unclear. In this study, antibody persistence up to 10 years after previous vaccination of adolescents (N=478) with combined reduced-antigen-content diphtheria-tetanus-acellular pertussis vaccine (dTpa, Boostrix™, GlaxoSmithKline Belgium) containing 0.5mg, 0.3mg or 0.133mg of aluminium was assessed. The immunogenicity, reactogenicity and safety of a decennial booster dTpa dose were also investigated. METHODS: Young adults vaccinated as adolescents in the initial booster study were invited to participate in an assessment of antibody persistence at years 8.5 and 10, and to receive a dTpa booster dose at year 10 with immunogenicity assessment one month later. Those who originally received the 0.5mg or 0.3mg formulations received the same vaccine at year 10. Those in the 0.133mg group received the 0.5mg formulation. Reactogenicity and safety endpoints were captured until 30 days after booster vaccination. RESULTS: Prior to the decennial booster at year 8.5 and year 10, all participants had seroprotective antibodies for diphtheria (ELISA or neutralisation assay) and tetanus. At least 77.8% were seropositive for anti-pertussis toxin (PT) antibodies at year 8.5 and 82.8% at year 10. All participants were seropositive for antibodies for filamentous haemagglutinin and pertactin at both time points. The decennial booster dose induced robust increases in antibody GMCs to all antigens. The post-booster anti-PT geometric mean concentration was 82.5EL.U/ml (95%CI 67.0-101.6) and 124.0 (103.5-148.5) in the 0.3mg and 0.5mg groups, respectively. The reactogenicity and safety profile of the decennial booster dose was consistent with the known safety profile of dTpa. No serious adverse events were reported. CONCLUSIONS: Decennial booster vaccination with either of the two licensed formulations of dTpa was highly immunogenic and well tolerated in young adults. Either formulation could be confidently used as a decennial booster. This study is registered at www.clinicaltrials.govNCT01147900.

Early exposure to thimerosal-containing vaccines and children's cognitive development. A 9-year prospective birth cohort study in Poland.

UNLABELLED: The controversial topic of the early exposure to mercury is regarding ethylmercury, which is present in the thimerosal-containing vaccines (TCVs). The objective of this study was to determine the relationship between the early exposure to TCVs and cognitive development in children during the first 9 years of life. The cohort included 318 children vaccinated in an early period (neonatal and up to 6 months) against hepatitis B and diphtheria-tetanus-pertussis (DTP) using formulation with or without thimerosal. The children's development was assessed using the Fagan test (6th month of life), the Bayley Scales of Infant Development (BSID)-II (12th-36th month), the Raven test (5th, 8th year), and the Wechsler Intelligence Scale for Children (WISC-R) (6th, 7th, 9th year). Results were determined by multivariable linear and logistic regression, adjusted to potential confounders. Children exposed and not exposed to TCVs in the neonatal period had similar outcomes of cognitive-developmental tests; only the results of BSID-II at the 36th month and WISC-R at the 9th year were significantly higher for those exposed to TCVs. Developmental test results in children exposed to TCVs up to the 6th month of life also did not depend on thimerosal dose. CONCLUSION: TCV administration in early infancy did not affect children's cognitive development.

How common are long-lasting, intensely itching vaccination granulomas and contact allergy to aluminium induced by currently used pediatric vaccines? A prospective cohort study.

UNLABELLED: The frequency of long-lasting, intensely itching subcutaneous nodules at the injection site for aluminium (Al)-adsorbed vaccines (vaccination granulomas) was investigated in a prospective cohort study comprising 4,758 children who received either a diphtheria-tetanus-pertussis-polio-Haemophilus influenzae type b vaccine (Infanrix®, Pentavac®) alone or concomitant with a pneumococcal conjugate (Prevenar). Both vaccines were adsorbed to an Al adjuvant. Altogether 38 children (0.83 %) with itching granulomas were identified, epicutaneously tested for Al sensitisation and followed yearly. Contact allergy to Al was verified in 85 %. The median duration of symptoms was 22 months in those hitherto recovered. The frequency of granulomas induced by Infanrix® was >0.66 % and by Prevenar >0.35 %. The risk for granulomas increased from 0.63 to 1.18 % when a second Al-adsorbed vaccine was added to the schedule. CONCLUSION: Long-lasting itching vaccination granulomas are poorly understood but more frequent than previously known after infant vaccination with commonly used diphtheria-tetanus-pertussis-polio-Haemophilus influenzae type b and pneumococcal conjugate vaccines. The risk increases with the number of vaccines given. Most children with itching granulomas become contact allergic to aluminium. Itching vaccination granulomas are benign but may be troublesome and should be recognised early in primary health care to avoid unnecessary investigations, anxiety and mistrust.

Distribution of aluminum in hair of Brazilian infants and correlation to aluminum-adjuvanted vaccine exposure.

BACKGROUND: Nursing children are exposed to dietary aluminum (in breast milk and/or infant formulas) and through aluminum-adjuvanted vaccines (AAVs). We studied total hair-Al concentrations of nursing children that had been immunized with hepatitis B, DTP, and meningococcal vaccines. METHODS: We studied the hair of 37 young children (aged 26 to 824 days) who were exposed to cumulative doses of Al ranging from 0.63 to 6.88 mg from AAVs. Graphite furnace atomic absorption spectrometry was used to reliably measure total Al concentrations in hair samples. RESULTS: The analytical method proved sensitive enough to quantify Al in the hair of nursing children. At current levels of exposure it is possible to determine total Al in hair sample of 1.65 mg. Cumulative doses of AAV in children ranged from 0.63 to 6.88 mg Al. Median hair-Al was 47.7 µg g⁻¹ (ranging from 12.2 to 221.9 µg g⁻¹). There was no statistically significant correlation between hair-Al concentration and age of child (r=-0.049; p=0.774), total exposure from vaccine (r=-0.078; p=0.643), or the time elapsed after the last AAVs (r=0.015; p=0.931). CONCLUSION: Aluminum in children's hair can be reliably measured but we are still uncertain how representative it can be of the Al body burden.

A freeze-stable formulation for DTwP and DTaP vaccines.

Inadvertent vaccine freezing often occurs in the cold chain and may cause damage to freeze­sensitive vaccines. Liquid vaccines that contain aluminum salt adjuvants are particularly vulnerable. Polyol cryoprotective excipients have been shown to prevent freeze damage to hepatitis B vaccine. In this study, we examined the freeze-protective effect of propylene glycol on diphtheria-tetanus-pertussis-whole-cell (DTwP) and acellular (DTaP) vaccines. Pilot lots of DTwP and DTaP formulated with 7.5% propylene glycol underwent 3 freeze-thaw treatments. The addition of propylene glycol had no impact on pH, particle size distribution, or potency of the vaccines prior to freeze-thaw treatment; the only change noted was an increase in osmolality. The potencies and the physical properties of the vaccines containing cryoprotectant were maintained after freeze-thawing and for 3 months in accelerated stability studies. The results from this study indicate that formulating vaccines with propylene glycol can protect diphtheria-tetanus-pertussis vaccines against freeze damages.

Pharmacokinetic modeling as an approach to assessing the safety of residual formaldehyde in infant vaccines.

Formaldehyde is a one-carbon, highly water-soluble aldehyde that is used in certain vaccines to inactivate viruses and to detoxify bacterial toxins. As part of the manufacturing process, some residual formaldehyde can remain behind in vaccines at levels less than or equal to 0.02%. Environmental and occupational exposure, principally by inhalation, is a continuing risk assessment focus for formaldehyde. However, exposure to formaldehyde via vaccine administration is qualitatively and quantitatively different from environmental or occupational settings and calls for a different perspective and approach to risk assessment. As part of a rigorous and ongoing process of evaluating the safety of biological products throughout their lifecycle at the FDA, we performed an assessment of formaldehyde in infant vaccines, in which estimates of the concentrations of formaldehyde in blood and total body water following exposure to formaldehyde-containing vaccines at a single medical visit were compared with endogenous background levels of formaldehyde in a model 2-month-old infant. Formaldehyde levels were estimated using a physiologically-based pharmacokinetic (PBPK) model of formaldehyde disposition following intramuscular (IM) injection. Model results indicated that following a single dose of 200 µg, formaldehyde is essentially completely removed from the site of injection within 30 min. Assuming metabolism at the site of injection only, peak concentrations of formaldehyde in blood/total body water were estimated to be 22 µg/L, which is equivalent to a body burden of 66 µg or <1% of the endogenous level of formaldehyde. Predicted levels in the lymphatics were even lower. Assuming no adverse effects from endogenous formaldehyde, which exists in blood and extravascular water at background concentrations of 0.1 mM, we conclude that residual, exogenously applied formaldehyde continues to be safe following incidental exposures from infant vaccines.

Review of a new fully liquid, hexavalent vaccine: Hexaxim.

INTRODUCTION: The introduction of injectable vaccines targeting new diseases into childhood immunization programs has resulted in the need for combination vaccines to reduce the number of injections given during early childhood and maintain acceptability of targeting multiple pathogens by vaccination. Currently, there is only one licensed hexavalent combination vaccine which targets diphtheria, polio, tetanus, Haemophilus influenzae type b, hepatitis B and pertussis. A new, fully liquid formulation hexavalent vaccine ( Hexaxim ) has been developed and is currently undergoing licensure for use in childhood immunization programs. AREAS COVERED: Safety and immunogenicity studies of Hexaxim have been undertaken in a diversity of settings, been evaluated with different dosing schedules and in comparison to the other licensed hexavalent vaccine (Infanrix hexa). This review of published journal articles and conference proceeding is focused on the studies in which Hexaxim has been evaluated and which are contributing to its pending licensure. Non-inferiority was demonstrated at the level of proportion of children developing seroprotective titers or showing seroconversion following the primary series of vaccine compared to the same target-antigens included in licensed combination vaccines. Also, Hexaxim was associated with a favorable safety and tolerability profile when administered during the first 6 months of life. Adequate and robust memory responses were elicited following a booster dose in the second year of life. EXPERT OPINION: The development of new hexavalent combination vaccines targeting established pathogens is likely to assist in improving compliance and timeliness of vaccination in infants. These formulations will, however, need to be monitored for medium- and long-term effectiveness amidst growing concern of waning immunity against diseases such as pertussis when using acellular-pertussis vaccine and possibly hepatitis B when using combination vaccines. Nevertheless, the development of such combination vaccines remains necessary to help with the introduction of other new vaccines into an already crowded childhood immunization schedules.

A child with a long-standing, intensely itching subcutaneous nodule on a thigh: an uncommon (?) reaction to commonly used vaccines.

A 2-year-old girl presented with an intensely itching subcutaneous nodule on the front of a thigh. The nodule persisted for 10 months until it was excised. Subsequent investigation for malignancy and systemic disease showed no pathological findings. The diagnosis, persistent itching vaccination granuloma, was revealed by hazard almost 2 years after the onset of symptoms. Persistent itching subcutaneous nodules at the injection site for aluminium containing vaccines (mostly diphtheria-tetanus-pertussis combination vaccines for primary immunisation of infants) may appear with a long delay after the vaccination (months), cause prolonged itching (years) and are often associated with contact allergy to aluminium. The condition is poorly recognised in Health Care which may lead to prolonged symptoms and unnecessary investigations.

Trace determination of free formaldehyde in DTP and DT vaccines and diphtheria-tetanus antigen by single drop microextraction and gas chromatography-mass spectrometry.

An immersed single drop microextraction (SDME) method was successfully developed for the trace enrichment of formaldehyde from DTP and DT vaccines and diphtheria-tetanus antigen. The formaldehyde was derivatized by means of the Hantzsch reaction. The dehydropyridine derivative was extracted into a microdrop of chloroform that suspended in a 4 ml sample solution for a preset time. The microdrop was then retracted into the microsyringe and injected directly into a gas chromatography-mass spectrometry (GC-MS) injection port. Effects of different parameters such as the type of solvent, extraction time, stirring rate, and temperature were studied and optimized. The limit of detection was 0.22 ng/l and relative standard deviation (RSD) value was 6.2% (n=5). The regression coefficient was satisfactory (r(2)=0.992) and linear range was obtained from 1 to 500 ng/l.

Principal component analysis and discrimination of variables associated with pre- and post-natal exposure to mercury.

The variance of variables associated with neurodevelopment at 180 days, pre-natal variables (Hg in placenta, blood and hair) and post-natal Hg exposure (including Thimerosal-containing vaccines, TCV) were examined in 82 exclusively breastfed infants using principal component analysis (PCA). This multivariate method was applied to identify hierarchy and sets of interrelated variables. The PCA yielded a two-factor solution, explaining 92% of variance and summarizing most of the relevant information in the dataset matrix: the first component represented birth weight and vaccine (first doses of Hepatitis B and DTP) variability and explained 57% of variance; the second component represented a gradient of neurodevelopment (Gesell scores) and explained 35% of variance. The third component explained only 3% of the remaining 8% variance. Beside CNS priming by breastfeeding, infant development (birth weight) and time of immunization with TCV should be considered in epidemiological studies. PCA can classify sets of variables related to vaccination and neuromotor development schedules, clearly discriminating between earlier and later TCV exposures of exclusively breastfed infants. In conclusion, the incommensurable concept of the chance of toxic risk caused by TCV-EtHg exposure against the proven benefit of immunization is in no way disputed here. However, infant neurodevelopmental (ND) disorders linked to Thimerosal-Hg stands in need of proof, but PCA points to the possibility of identifying exposure risk variables associated with ND schedules.

A simple and rapid method for quantifying 2-phenoxyethanol (2-PE) in Diphtheria, Tetanus and w-Pertussis (DTwP) vaccine.

The authors developed a simple and rapid method for quantitation of 2-phenoxyethanol (2-PE) in DTwP vaccine based on reverse phase high performance liquid chromatography (HPLC). The method was simple and reproducible. The sensitivity of the assay was confirmed by spiking known amounts of 2-phenoxyethanol to the vaccine sample.

Boostrix (GlaxoSmithKline).

GlaxoSmithKline plc has developed and launched Boostrix, a subunit vaccine for use in adolescents and adults as a booster immunization against diphtheria, tetanus and pertussis (DTPa) infections.