Quo vadis en vacunas: desde la aproximación empírica a la nueva oleada tecnológica / Quo vadis in vaccines: from the empirical approach to the new wave of technology

El desarrollo de vacunas es un proceso multifactorial que ha evolucionado especialmente en las últimas décadas. La búsqueda de vacunas inmunógenas que resulten suficientemente seguras y tolerables ha dado lugar a sucesivos avances tecnológicos en este campo. Históricamente la tecnología aplicada a las vacunas puede dividirse en 3 aproximaciones: la empírica, la moderna y la nueva oleada tecnológica. Dentro de la primera se encuentran las vacunas basadas en microorganismos enteros, las técnicas de atenuación, inactivación, los cultivos celulares y las vacunas de subunidades. En la época moderna destacan los avances relacionados con la conjugación química, así como la tecnología de ADN recombinante y la vacunología inversa. Finalmente, en la nueva oleada tecnológica se incluye, entre otros, la bioconjugación, los vectores virales, la biología sintética, la autoamplificación del ARN mensajero, los módulos generalizados para antígenos de membrana, la vacunología estructural y los nuevos adyuvantes

The development of vaccines is a multifactorial process that has evolved and expanded, particularly over the last decades. The search for immunogenic vaccines that are also acceptably safe and tolerable enacted continuous technological advances in this field. In this regard, the technology applied to vaccines can historically be divided into 3 approaches: the empirical approach, the modern approach, and the new technological wave. The empirical approach for vaccine development includes whole micro-organisms, attenuation, inactivation, cell cultures and sub-unit vaccines. The modern approach contributed to leaps and bounds to vaccine development using chemical conjugation, as well as recombinant protein DNA technology and reverse vaccinology. Lastly, the new technological wave includes, among others, bioconjugation, viral vectors, synthetic biology, self-amplification of messenger RNA, generalized modules for membrane antigens, structural vaccinology and the new adjuvants

[Quo vadis in vaccines: From the empirical approach to the new wave of technology]. / Quo vadis en vacunas: desde la aproximación empírica a la nueva oleada tecnológica.

The development of vaccines is a multifactorial process that has evolved and expanded, particularly over the last decades. The search for immunogenic vaccines that are also acceptably safe and tolerable enacted continuous technological advances in this field. In this regard, the technology applied to vaccines can historically be divided into 3 approaches: the empirical approach, the modern approach, and the new technological wave. The empirical approach for vaccine development includes whole micro-organisms, attenuation, inactivation, cell cultures and sub-unit vaccines. The modern approach contributed to leaps and bounds to vaccine development using chemical conjugation, as well as recombinant protein DNA technology and reverse vaccinology. Lastly, the new technological wave includes, among others, bioconjugation, viral vectors, synthetic biology, self-amplification of messenger RNA, generalized modules for membrane antigens, structural vaccinology and the new adjuvants.

The social network around influenza vaccination in health care workers: a cross-sectional study.

BACKGROUND: Influenza vaccination coverage remains low among health care workers (HCWs) in many health facilities. This study describes the social network defined by HCWs' conversations around an influenza vaccination campaign in order to describe the role played by vaccination behavior and other HCW characteristics in the configuration of the links among subjects. METHODS: This study used cross-sectional data from 235 HCWs interviewed after the 2010/2011 influenza vaccination campaign at the Hospital Clinic of Barcelona (HCB), Spain. The study asked: "Who did you talk to or share some activity with respect to the seasonal vaccination campaign?" Variables studied included sociodemographic characteristics and reported conversations among HCWs during the influenza campaign. Exponential random graph models (ERGM) were used to assess the role of shared characteristics (homophily) and individual characteristics in the social network around the influenza vaccination campaign. RESULTS: Links were more likely between HCWs who shared the same professional category (OR 3.13, 95% CI = 2.61-3.75), sex (OR 1.34, 95% CI = 1.09-1.62), age (OR 0.7, 95% CI = 0.63-0.78 per decade of difference), and department (OR 11.35, 95% CI = 8.17-15.64), but not between HCWs who shared the same vaccination behavior (OR 1.02, 95% CI = 0.86-1.22). Older (OR 1.26, 95% CI = 1.14-1.39 per extra decade of HCW) and vaccinated (OR 1.32, 95% CI = 1.09-1.62) HCWs were more likely to be named. CONCLUSIONS: This study finds that there is no homophily by vaccination status in whom HCWs speak to or interact with about a workplace vaccination promotion campaign. This result highlights the relevance of social network analysis in the planning of health promotion interventions.

Pertussis vaccination during pregnancy: Antibody persistence in infants.

Maternal pertussis vaccination is associated with higher levels of pertussis antibodies at birth. We assessed the persistence of pertussis antibodies until primary vaccination in infants whose mothers received Tdap (tetanus, diphtheria, acellular pertussis) vaccine during pregnancy. Infants were born at the Hospital Clinic of Barcelona (Spain) in November 2014. Anti-PT IgG was determined by ELISA at delivery, between the first and second month of life, and estimated at 2months of age. The study included 37 infants whose mothers received Tdap between 21 and 38weeks of gestation. Infants presented a decline in GMC of anti-PT IgG between peripartum and follow-up levels, 52.7 (95% CI 34.7-80.2) versus 7.5 (95% CI 4.2-13.3) at 2months of age (p<0.001). The median half-life of maternal antibodies was 47days. More than half (51.4%) the infants presented detectable anti-PT IgG before the start of primary infant vaccination.

Immunogenicity and immunization costs of adjuvanted versus non-adjuvanted hepatitis B vaccine in chronic kidney disease patients.

Hepatitis B virus (HBV) vaccination is recommended for all susceptible chronic pre-hemodialysis and hemodialysis patients. This study assessed the immunogenicity of HBV vaccines (adjuvanted and non-adjuvanted) in chronic kidney disease patients vaccinated at the Hospital Clinic of Barcelona (Spain) between January 2007 and July 2012. In addition, the costs for the health system were evaluated accor-ding to the proportion of vaccine responders after receiving either vaccine. Patients receiving 3 doses of hepatitis B adjuvanted vaccine were 3 times more likely to seroconvert than patients immunized with non-adjuvanted vaccines, OR 3.56 (95% CI 1.84-6.85). This resulted in fewer patients requiring a second course of HBV vaccination and fewer outpatient visits, saving more than €9,500 per 100 patients. The higher immunogenicity of the adjuvanted HBV vaccine would counterbalance the lower costs associated with the non-adjuvanted vaccine.

Safety and Tolerability of Alveolar Type II Cell Transplantation in Idiopathic Pulmonary Fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited response to currently available therapies. Alveolar type II (ATII) cells act as progenitor cells in the adult lung, contributing to alveolar repair during pulmonary injury. However, in IPF, ATII cells die and are replaced by fibroblasts and myofibroblasts. In previous preclinical studies, we demonstrated that ATII-cell intratracheal transplantation was able to reduce pulmonary fibrosis. The main objective of this study was to investigate the safety and tolerability of ATII-cell intratracheal transplantation in patients with IPF. METHODS: We enrolled 16 patients with moderate and progressive IPF who underwent ATII-cell intratracheal transplantation through fiberoptic bronchoscopy. We evaluated the safety and tolerability of ATII-cell transplantation by assessing the emergent adverse side effects that appeared within 12 months. Moreover, pulmonary function, respiratory symptoms, and disease extent during 12 months of follow-up were evaluated. RESULTS: No significant adverse events were associated with the ATII-cell intratracheal transplantation. After 12 months of follow-up, there was no deterioration in pulmonary function, respiratory symptoms, or disease extent. CONCLUSIONS: Our results support the hypothesis that ATII-cell intratracheal transplantation is safe and well tolerated in patients with IPF. This study opens the door to designing a clinical trial to elucidate the potential beneficial effects of ATII-cell therapy in IPF.

Sistema de autodeclaración de acontecimientos adversos y cobertura de vacunación antigripal en profesionales sanitarios en un hospital universitario de tercer nivel / Adverse events self-declaration system and influenza vaccination coverage of healthcare workers in a tertiary hospital

Introducción: Durante la campaña de vacunación antigripal 2011-2012 establecimos un sistema de autodeclaración de acontecimientos adversos (AA) en el personal sanitario (PS). El objetivo de este estudio es describir la población vacunada y analizar la cobertura de vacunación y los AA autodeclarados tras la vacunación voluntaria del PS frente a la gripe en un hospital universitario de tercer nivel en Barcelona. Métodos: Estudio observacional. Para el cálculo de la cobertura de vacunación se utilizó el registro de vacunación de profesionales sanitarios del hospital. Los AA se recogieron mediante una encuesta voluntaria, anónima y autoadministrada durante la campaña de vacunación antigripal 2011-2012, y se analizaron mediante regresión logística. Se construyó un modelo de regresión logística para determinar los factores que predisponen a declarar AA. Resultados: La campaña alcanzó una cobertura de vacunación antigripal del 30,5% (n = 1.507/4.944) del PS. De los vacunados, el 23,8% (n = 358) respondieron la encuesta de AA autodeclarados. El 52,0% (n = 186) de los que respondieron a la encuesta declaró haber presentado algún tipo de AA. De estos, el 75,3% (n = 140) refirió signos y síntomas locales tras la vacunación, el 9,7% (n = 18), signos y síntomas sistémicos, y el 15,1% (n = 28), síntomas tanto locales como sistémicos. No se declaró ningún AA grave. Ser mujer y tener menos de 35 años se asoció a declarar algún tipo de AA. Conclusiones: El sistema de autodeclaración no registró AA graves en el PS, suponiendo una oportunidad para aumentar la confianza del PS en la vacuna antigripal (AU)

Introduction: During the influenza vaccination campaign 2011-2012 we established a self-declaration system of adverse events (AEs) in healthcare workers (HCW). The aim of this study is to describe the vaccinated population and analyse vaccination coverage and self-declared AEs after the voluntary flu vaccination in a university hospital in Barcelona. Methods: Observational study. We used the HCW immunization record to calculate the vaccination coverage. We collected AEs using a voluntary, anonymous, self-administered survey during the 2011-2012 flu vaccination campaign. We performed a logistic regression model to determine the associated factors to declare AEs. Results: The influenza vaccination coverage in HCW was 30.5% (n = 1,507/4,944). We received completed surveys from 358 vaccinated HCW (23.8% of all vaccinated). We registered AEs in 186 respondents to the survey (52.0% of all respondents). Of these, 75.3% (n = 140) reported local symptoms after the flu vaccination, 9.7% (n = 18) reported systemic symptoms and 15.1% (n = 28) both local and systemic symptoms. No serious AEs were self-reported. Female sex and aged under 35 were both factors associated with declaring AEs. Conclusions: Our self-reporting system did not register serious AEs in HCW, resulting in an opportunity to improve HCW trust in flu vaccination (AU)

[Adverse events self-declaration system and influenza vaccination coverage of healthcare workers in a tertiary hospital]. / Sistema de autodeclaración de acontecimientos adversos y cobertura de vacunación antigripal en profesionales sanitarios en un hospital universitario de tercer nivel.

INTRODUCTION: During the influenza vaccination campaign 2011-2012 we established a self-declaration system of adverse events (AEs) in healthcare workers (HCW). The aim of this study is to describe the vaccinated population and analyse vaccination coverage and self-declared AEs after the voluntary flu vaccination in a university hospital in Barcelona. METHODS: Observational study. We used the HCW immunization record to calculate the vaccination coverage. We collected AEs using a voluntary, anonymous, self-administered survey during the 2011-2012 flu vaccination campaign. We performed a logistic regression model to determine the associated factors to declare AEs. RESULTS: The influenza vaccination coverage in HCW was 30.5% (n=1,507/4,944). We received completed surveys from 358 vaccinated HCW (23.8% of all vaccinated). We registered AEs in 186 respondents to the survey (52.0% of all respondents). Of these, 75.3% (n=140) reported local symptoms after the flu vaccination, 9.7% (n=18) reported systemic symptoms and 15.1% (n=28) both local and systemic symptoms. No serious AEs were self-reported. Female sex and aged under 35 were both factors associated with declaring AEs. CONCLUSIONS: Our self-reporting system did not register serious AEs in HCW, resulting in an opportunity to improve HCW trust in flu vaccination.

Recomendaciones autonómicas en vacunación de hepatitis en adultos infectados por el virus de la inmunodeficiencia humana: ¿disparidad basada en la evidencia? / Regional recommendations on hepatitis vaccination in human immunodeficiency virus infected adult patients in Spain: evidence-based disparity?

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Vaccinations in prisons: A shot in the arm for community health.

From the first day of imprisonment, prisoners are exposed to and expose other prisoners to various communicable diseases, many of which are vaccine-preventable. The risk of acquiring these diseases during the prison sentence exceeds that of the general population. This excess risk may be explained by various causes; some due to the structural and logistical problems of prisons and others to habitual or acquired behaviors during imprisonment. Prison is, for many inmates, an opportunity to access health care, and is therefore an ideal opportunity to update adult vaccination schedules. The traditional idea that prisons are intended to ensure public safety should be complemented by the contribution they can make in improving community health, providing a more comprehensive vision of safety that includes public health.

Protecting newborns against pertussis: the value of vaccinating during pregnancy.

Resurgence of pertussis has recently been reported in several countries with long-standing pertussis immunization and high vaccination coverage. This situation requires consideration of alternative immunization strategies to protect newborns. In the absence of a vaccine that confers long-lasting immunity, maternal vaccination for pertussis during pregnancy seems to be a safe, immunogenic, effective and accepted strategy to protect infants during the first weeks of life. The existing scientific evidence provides the grounds for pregnant women and healthcare workers to make informed decisions regarding this measure as well as for countries with high pertussis-related infant morbidity and mortality that should consider implementation. Furthermore, this could be a promising strategy to address other vaccine-preventable diseases of pregnancy and the neonatal period.

Rubella susceptibility in pregnant women and results of a postpartum immunization strategy in Catalonia, Spain.

BACKGROUND: Elimination of congenital rubella syndrome depends not only on effective childhood immunization but also on the identification and immunization of rubella susceptible women. We assessed rubella susceptibility among pregnant women and evaluated the adherence and response to postpartum immunization with measles, mumps and rubella (MMR) vaccine. METHODS: Cross-sectional study of women who gave birth at the Hospital Clinic de Barcelona (Spain) between January 2008 and December 2013. Antenatal serological screening for rubella was performed in all women during pregnancy. In rubella-susceptible women, two doses of MMR vaccine were recommended following birth. We evaluated rubella serological response to MMR vaccination in mothers who complied with the recommendations. RESULTS: A total of 22,681 pregnant women were included in the study. The mean age was 32.3 years (SD 5.6), and 73.6% were primipara. The proportion of immigrants ranged from 43.4% in 2010 to 38.5% in 2012. The proportion of women susceptible to rubella was 5.9% (1328). Susceptibility to rubella declined with increasing maternal age. Immigrant pregnant women were more susceptible to rubella (7.6%) than women born in Spain (4.6%). Multivariate analyses showed that younger age (≤19 years) aOR 1.7 (95% CI 1.1-2.5), primiparas aOR 1.3 (95% CI 1.1-1.5) and immigrant women aOR 1.6 (95% CI 1.4-1.8) were more likely to be susceptible. The second dose of MMR vaccine was received by 57.2% (718/1256) of rubella-susceptible women, with the highest proportion being immigrant women compared with women born in Spain. After vaccination, all women showed rubella immunity. CONCLUSIONS: The higher rubella susceptibility found in the three youngest age groups and in immigrant women highlights the relevance of antenatal screening, in order to ensure identification and postpartum immunization. The postpartum immunization strategy is an opportunity to protect women of childbearing age and consequently prevent occurrence of CRS, and to increase vaccination coverage against rubella and other vaccine-preventable diseases.

Combined tetanus-diphtheria and pertussis vaccine during pregnancy: transfer of maternal pertussis antibodies to the newborn.

BACKGROUND AND OBJECTIVES: Pertussis is currently an emerging public health concern in some countries with high vaccination coverage. It is expected that maternal pertussis immunization could provide newborn protection. We compared pertussis toxin antibody (anti-PT) levels in women during pregnancy (pre- and post-vaccination) with respect to levels in the newborn at delivery in women vaccinated during pregnancy. We also estimated anti-PT titers at primary infant vaccination. METHODS: Observational study of pregnant women vaccinated with Tdap (≥20 weeks gestation) and their newborns between May 2012 and August 2013. Anti-PT levels were determined by ELISA in maternal (pre- and post-vaccination) and newborn blood. RESULTS: Pre-vaccination, post-vaccination maternal and newborn samples were available in 132 subjects. Mean maternal age was 34.2 (SD 4.3) years. Median weeks of gestation at vaccination were 27.2 (Q1-Q3 21.7-30.8). Anti-PT (≥10 IU/ml) levels were found in 37.1% of maternal pre-vaccination samples (geometric mean titer (GMT) 7.9 IU/ml (95% CI 6.8-9.2)), 90.2% of post-vaccination samples (GMT 31.1 IU/ml (95% CI 26.6-36.3)) and 94.7% of newborns (GMT 37.8 IU/ml (95% CI 32.3-44.1)). The Lin concordance index between post-vaccination maternal and newborn samples was 0.8 (95% CI 0.8-0.9). Transplacental transfer ratio was 146.6%. At two months of age, 66% of newborns had estimated anti-PT levels ≥10 IU/ml. CONCLUSIONS: There was a high correlation between anti-PT levels in mothers and newborns, with higher levels in newborns, which should be sufficient to provide protection against pertussis during the first months of life. Vaccination of pregnant women seems to be an immunogenic strategy to protect newborns until primary infant immunization.

Seroprevalence study of B. pertussis infection in health care workers in Catalonia, Spain.

Pertussis is a re-emerging infection in countries with high infant immunization coverage. Healthcare workers (HCW) are exposed and can transmit the infection to especially-vulnerable patients. Therefore, pertussis vaccination of HCW is recommended. Between June 2008 and December 2010, 460 HCW from hospital and primary healthcare centers were recruited to determine susceptibility to pertussis. IgG antibodies against pertussis (anti-pertussis ab) were measured, using a routine technique that detects antibodies against pertussis including pertussis toxin (PT) and filamentous hemagglutinin (FHA). Positive results were confirmed with a more-specific technique that only assesses anti-PT IgG antibodies. The median age was 42 years (range, 21-65), 77.3% were female. 172 were nurses, 133 physicians, 60 other clinical workers and 95 non-clinical workers. None had received pertussis vaccination since childhood. The overall prevalence of anti-pertussis antibodies was 51.7%, (95% CI 47.1-56.4). Anti-PT antibodies were determined in the 220 HCW with positive anti-pertussis antibodies: 4 (1.8%) were negative and 33 (15%) had a high titer (≥ 45 IU/mL). No significant differences between the prevalence of anti-pertussis antibodies or anti-TP antibodies were found according to age, type of occupation or type of center. Our study confirms the need for vaccination of HCW because at least half are susceptible to pertussis. High anti-PT titers found in 15% of seropositive HCW showed that they had had recent contact with B. pertussis.

Superior antigen-specific CD4+ T-cell response with AS03-adjuvantation of a trivalent influenza vaccine in a randomised trial of adults aged 65 and older.

BACKGROUND: The effectiveness of trivalent influenza vaccines may be reduced in older versus younger adults because of age-related immunosenescence. The use of an adjuvant in such a vaccine is one strategy that may combat immunosenescence, potentially by bolstering T-cell mediated responses. METHODS: This observer-blind study, conducted in the United States (US) and Spain during the 2008-2009 influenza season, evaluated the effect of Adjuvant System AS03 on specific T-cell responses to a seasonal trivalent influenza vaccine (TIV) in ≥65 year-old adults.Medically-stable adults aged ≥65 years were randomly allocated to receive a single dose of AS03-adjuvanted TIV (TIV/AS03) or TIV. Healthy adults aged 18-40 years received only TIV. Blood samples were collected on Day 0, Day 21, Day 42 and Day 180. Influenza-specific CD4+ T cells, defined by the induction of the immune markers CD40L, IL-2, IFN-γ, or TNF-α, were measured in ex vivo cultures of antigen-stimulated peripheral blood mononuclear cells. RESULTS: A total of 192 adults were vaccinated: sixty nine and seventy three ≥65 year olds received TIV/AS03 and TIV, respectively; and fifty 18 - 40 year olds received TIV. In the ≥65 year-old group on Day 21, the frequency of CD4+ T cells specific to the three vaccine strains was superior in the TIV/AS03 recipients to the frequency in TIV (p < 0.001). On Days 42 and 180, the adjusted-geometric mean specific CD4+ T-cell frequencies were also higher in the TIV/AS03 recipients than in the TIV recipients (p < 0.001). Furthermore, the adjusted-geometric mean specific CD4+ T-cell frequencies were higher in the ≥65 year-old recipients of TIV/AS03 than in the18 - 40 year old recipients of TIV on Days 21 (p = 0.006) and 42 (p = 0.011). CONCLUSION: This positive effect of AS03 Adjuvant System on the CD4+ T-cell response to influenza vaccine strains in older adults could confer benefit in protection against clinical influenza disease in this population. TRIAL REGISTRATION: (Clinicaltrials.gov.). NCT00765076.

Effects of different antigenic stimuli on thymic function and interleukin-7/CD127 system in patients with chronic HIV infection.

BACKGROUND: We tested if an increase in immune activation and a decrease in CD4⁺ T cells induced by different antigenic stimuli could be associated with changes in the thymic function and the interleukin (IL)-7/CD127 system. METHODS: Twenty-six HIV-infected patients under combined antiretroviral therapy (cART) were randomized to receive, during 12 months, a complete immunization schedule (7 vaccines and 15 doses) or placebo. Thereafter, cART was interrupted during 6 months. Changes in the thymic function and the IL-7/CD127 system after 3 different antigenic stimuli (vaccines, episodes of low-level intermittent viremia before cART interruption, or viral load rebound after cART interruption) were assessed. RESULTS: During the period on cART, neither vaccines nor low-level viremia influenced thymic function or IL-7/CD127 system parameters. By analyzing the cohort as a whole while on cART, a significant improvement was observed in the thymic function as measured by an increase in the thymic volume (P = 0.024), T-cell receptor excision circle-bearing cells (P = 0.012), and naive CD4⁺ and CD8⁺ T cells (P = 0.069 both). No significant changes were observed in the IL-7/CD127 system. After cART interruption, a decrease in T-cell receptor excision circles (P < 0.001) and naive CD8⁺ T cells (P < 0.001), an increase in IL-7 and expression of CD127 on naive and memory CD4⁺ T cells (P = 0.028, P = 0.088, and P = 0.04, respectively), and a significant decrease in CD127 on naive and memory CD8⁺ T cells (P = 0.01, P = 0.006, respectively) were observed. CONCLUSIONS: Low-level transient antigenic stimuli during cART were not associated with changes in the thymic function or the IL-7/CD127 system. Conversely, viral load rebound very early after cART interruption influenced the thymic function and the IL-7/CD127 system. Clinical Trials.gov number NCT00329251.

Vacunación integral en la embarazada / Comprehensive vaccination in pregnant women

La vacunación integral en la embarazada contempla la inmunización antes, durante o después de la gestación, y pretende proteger a la madre y al recién nacido. Se deben ponderar, de forma individualizada, los riesgos de padecer determinadas enfermedades frente a los potenciales beneficios y riesgos de la vacunación. En el contexto de enfermedades emergentes como la tos ferina, la actualización de las recomendaciones es de especial relevancia. En el presente trabajo se describen las principales estrategias de vacunación en la embarazada consensuadas por diversos organismos expertos en vacunas. Se revisan las vacunas indicadas durante el embarazo, y aquellas que se deberían considerar en el posparto inmediato o previamente a la gestación. Finalmente, se detallan las vacunas a valorar antes de realizar un viaje durante la gestación (AU)

Comprehensive vaccination in pregnancy is related to immunization before, during or after gestation, and aims to protect the mother and the newborn. The risks to which every pregnant woman is exposed and the potential benefits of vaccination must be evaluated on an individual basis. In the context of emerging infectious diseases such as pertussis, the need to update traditional recommendations is particularly important. This article describes the main vaccination strategies during pregnancy agreed by different expert institutions. The vaccines indicated during pregnancy, and those that should be considered in the immediate postpartum or prior to pregnancy are reviewed. Finally, the vaccines to be considered during pregnancy before international travel are discussed (AU)

Safety and immunogenicity of an AS01-adjuvanted varicella-zoster virus subunit candidate vaccine against herpes zoster in adults >=50 years of age.

BACKGROUND: An adjuvanted varicella-zoster virus glycoprotein E (gE) subunit vaccine candidate for herpes zoster is in development. In this trial we compared the safety, reactogenicity, and immunogenicity of the vaccine antigen combined with different adjuvant doses. METHODS: This was a phase II, observer-blind, randomized, multinational study. Adults ≥50 years old were randomized 4:4:2:1 to be vaccinated at months 0 and 2 with gE combined with a higher (AS01B) or lower (AS01E) dose adjuvant, unadjuvanted gE, or saline. Following each dose, solicited events were recorded for 7 days and unsolicited adverse events for 30 days. Serious adverse events were collected for 1 year. Cell-mediated and humoral immune responses were assessed at baseline and following each dose. RESULTS: No vaccine-related severe adverse events were reported. Solicited adverse events were generally mild to moderate and transient. For all gE-based vaccines, pain was the most common local symptom and fatigue the most common general symptom. Immune responses were significantly enhanced by AS01B and AS01E compared to unadjuvanted gE and were significantly stronger for gE/AS01B than for gE/AS01E. CONCLUSIONS: AS01 improved the immunogenicity of gE while retaining acceptable safety and reactogenicity profiles. The enhancement of gE-specific cellular and humoral responses was adjuvant dose dependent. CLINICAL TRIALS REGISTRATION: NCT00802464.