Endpoints in vaccine trials

Can incorporating genotyping data into efficacy estimators improve efficiency of early phase malaria vaccine trials?

BACKGROUND

Early phase malaria vaccine field trials typically measure malaria infection by PCR or thick blood smear microscopy performed on serially sampled blood. Vaccine efficacy (VE) is the proportion reduction in an endpoint due to vaccination and is often calculated as VEHR = 1-hazard ratio or VERR = 1-risk ratio. Genotyping information can distinguish different clones and distinguish multiple infections over time, potentially increasing statistical power. This paper investigates two alternative VE endpoints incorporating genotyping information: VEmolFOI, the vaccine-induced proportion reduction in incidence of new clones acquired over time, and VEC, the vaccine-induced proportion reduction in mean number of infecting clones per exposure.

METHODS

Power of VEmolFOI and VEC was compared to that of VEHR and VERR by simulations and analytic derivations, and the four VE methods were applied to three data sets: a Phase 3 trial of RTS,S malaria vaccine in 6912 African infants, a Phase 2 trial of PfSPZ Vaccine in 80 Burkina Faso adults, and a trial comparing Plasmodium vivax incidence in 466 Papua New Guinean children after receiving chloroquine + artemether lumefantrine with or without primaquine (as these VE methods can also quantify effects of other prevention measures). By destroying hibernating liver-stage P. vivax, primaquine reduces subsequent reactivations after treatment completion.

RESULTS

In the trial of RTS,S vaccine, a significantly reduced number of clones at first infection was observed, but this was not the case in trials of PfSPZ Vaccine or primaquine, although the PfSPZ trial lacked power to show a reduction. Resampling smaller data sets from the large RTS,S trial to simulate phase 2 trials showed modest power gains from VEC compared to VEHR for data like those from RTS,S, but VEC is less powerful than VEHR for trials in which the number of clones at first infection is not reduced. VEmolFOI was most powerful in model-based simulations, but only the primaquine trial collected enough serial samples to precisely estimate VEmolFOI. The primaquine VEmolFOI estimate decreased after most control arm liver-stage infections reactivated (which mathematically resembles a waning vaccine), preventing VEmolFOI from improving power.

CONCLUSIONS

The power gain from the genotyping methods depends on the context. Because input parameters for early phase power calculations are often uncertain, these estimators are not recommended as primary endpoints for small trials unless supported by targeted data analysis.

TRIAL REGISTRATIONS

NCT00866619, NCT02663700, NCT02143934.

Can incorporating genotyping data into efficacy estimators improve efficiency of early phase malaria vaccine trials?

Background

Early phase malaria vaccine field trials typically measure malaria infection by PCR or thick blood smear microscopy performed on serially sampled blood. Vaccine efficacy (VE) is the proportion reduction in an endpoint due to vaccination and is often calculated as V E H R = 1 - hazard ratio or V E R R = 1 - risk ratio. Genotyping information can distinguish different clones and distinguish multiple infections over time, potentially increasing statistical power. This paper investigates two alternative VE endpoints incorporating genotyping information: V E m o l F O I , the vaccine-induced proportion reduction in incidence of new clones acquired over time, and V E C , the vaccine-induced proportion reduction in mean number of infecting clones per exposure.

Methods

We used simulations and analytic derivations to compare power of these methods to V E H R and V E R R and applied them to three data sets: a Phase 3 trial of RTS,S malaria vaccine in 6912 African infants, a Phase 2 trial of PfSPZ Vaccine in 80 Burkina Faso adults, and a trial comparing Plasmodium vivax incidence in 466 Papua New Guinean children after receiving chloroquine + artemether lumefantrine with or without primaquine (as these VE methods can also quantify effects of other prevention measures). By destroying hibernating liver-stage P. vivax, primaquine reduces subsequent reactivations after treatment completion.

Results

The RTS,S vaccine significantly reduced the number of clones at first infection, but PfSPZ vaccine and primaquine did not. Resampling smaller data sets from the large RTS,S trial to simulate phase 2 trials showed modest power gains from V E C compared to V E H R for data like RTS,S, but V E C is less powerful than V E H R for vaccines which do not reduce the number of clones at first infection. V E m o l F O I was most powerful in model-based simulations, but only the primaquine trial collected enough serial samples to precisely estimate V E m o l F O I . The primaquine V E m o l F O I estimate decreased after most control arm liver-stage infections reactivated (which mathematically resembles a waning vaccine), preventing V E m o l F O I from improving power.

Conclusions

The power gain from the genotyping methods depends on the context. Because input parameters for early phase power calculations are often uncertain, we recommend against these estimators as primary endpoints for small trials unless supported by targeted data analysis.

Trial registrations

NCT00866619, NCT02663700, NCT02143934.

The Future of Epidemic and Pandemic Vaccines to Serve Global Public Health Needs

This Review initiates a wide-ranging discussion over 2023 by selecting and exploring core themes to be investigated more deeply in papers submitted to the Vaccines Special Issue on the "Future of Epidemic and Pandemic Vaccines to Serve Global Public Health Needs". To tackle the SARS-CoV-2 pandemic, an acceleration of vaccine development across different technology platforms resulted in the emergency use authorization of multiple vaccines in less than a year. Despite this record speed, many limitations surfaced including unequal access to products and technologies, regulatory hurdles, restrictions on the flow of intellectual property needed to develop and manufacture vaccines, clinical trials challenges, development of vaccines that did not curtail or prevent transmission, unsustainable strategies for dealing with variants, and the distorted allocation of funding to favour dominant companies in affluent countries. Key to future epidemic and pandemic responses will be sustainable, global-public-health-driven vaccine development and manufacturing based on equitable access to platform technologies, decentralised and localised innovation, and multiple developers and manufacturers, especially in low- and middle-income countries (LMICs). There is talk of flexible, modular pandemic preparedness, of technology access pools based on non-exclusive global licensing agreements in exchange for fair compensation, of WHO-supported vaccine technology transfer hubs and spokes, and of the creation of vaccine prototypes ready for phase I/II trials, etc. However, all these concepts face extraordinary challenges shaped by current commercial incentives, the unwillingness of pharmaceutical companies and governments to share intellectual property and know-how, the precariousness of building capacity based solely on COVID-19 vaccines, the focus on large-scale manufacturing capacity rather than small-scale rapid-response innovation to stop outbreaks when and where they occur, and the inability of many resource-limited countries to afford next-generation vaccines for their national vaccine programmes. Once the current high subsidies are gone and interest has waned, sustaining vaccine innovation and manufacturing capability in interpandemic periods will require equitable access to vaccine innovation and manufacturing capabilities in all regions of the world based on many vaccines, not just "pandemic vaccines". Public and philanthropic investments will need to leverage enforceable commitments to share vaccines and critical technology so that countries everywhere can establish and scale up vaccine development and manufacturing capability. This will only happen if we question all prior assumptions and learn the lessons offered by the current pandemic. We invite submissions to the special issue, which we hope will help guide the world towards a global vaccine research, development, and manufacturing ecosystem that better balances and integrates scientific, clinical trial, regulatory, and commercial interests and puts global public health needs first.

Artificial Intelligence-Based Data-Driven Strategy to Accelerate Research, Development, and Clinical Trials of COVID Vaccine

The global COVID-19 (coronavirus disease 2019) pandemic, which was caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in a significant loss of human life around the world. The SARS-CoV-2 has caused significant problems to medical systems and healthcare facilities due to its unexpected global expansion. Despite all of the efforts, developing effective treatments, diagnostic techniques, and vaccinations for this unique virus is a top priority and takes a long time. However, the foremost step in vaccine development is to identify possible antigens for a vaccine. The traditional method was time taking, but after the breakthrough technology of reverse vaccinology (RV) was introduced in 2000, it drastically lowers the time needed to detect antigens ranging from 5-15 years to 1-2 years. The different RV tools work based on machine learning (ML) and artificial intelligence (AI). Models based on AI and ML have shown promising solutions in accelerating the discovery and optimization of new antivirals or effective vaccine candidates. In the present scenario, AI has been extensively used for drug and vaccine research against SARS-COV-2 therapy discovery. This is more useful for the identification of potential existing drugs with inhibitory human coronavirus by using different datasets. The AI tools and computational approaches have led to speedy research and the development of a vaccine to fight against the coronavirus. Therefore, this paper suggests the role of artificial intelligence in the field of clinical trials of vaccines and clinical practices using different tools.

The SARS-CoV-2 mutations versus vaccine effectiveness: New opportunities to new challenges

Background

The SARS-CoV-2 coronavirus epidemic is hastening the discovery of the most efficient vaccines. The development of cost-effective vaccines seems to be the only solution to terminate this pandemic. However, the vaccines’ effectiveness has been questioned due to recurrent mutations in the SARS-CoV-2 genome. Most of the mutations are associated with the spike protein, a vital target for several marketed vaccines. Many countries were highly affected by the 2nd wave of the SARS-CoV-2, like the UK, India, Brazil and France. Experts are also alarming the further COVID-19 wave with the emergence of Omicron, which is highly affecting the South African populations. This review encompasses the detailed description of all vaccine candidates and COVID-19 mutants that will add value to design further studies to combat the COVID-19 pandemic.

Methods

The information was generated using various search engines like google scholar, PubMed, clinicaltrial.gov.in, WHO database, ScienceDirect, and news portals by using keywords SARS-CoV-2 mutants, COVID-19 vaccines, efficacy of SARS-CoV-2 vaccines, COVID-19 waves.

Results

This review has highlighted the evolution of SARS-CoV-2 variants and the vaccine efficacy. Currently, various vaccine candidates are undergoing several phases of development. Their efficacy still needs to check for newly emerged variants. We have focused on the evolution, multiple mutants, waves of the SARS-CoV-2, and different marketed vaccines undergoing various clinical trials and the design of the trials to determine vaccine efficacy.

Conclusion

Various mutants of SARS-CoV-2 arrived, mainly concerned with the spike protein, a key component to design the vaccine candidates. Various vaccines are undergoing clinical trial and show impressive results, but their efficacy still needs to be checked in different SARS-CoV-2 mutants. We discussed all mutants of SARS-CoV-2 and the vaccine’s efficacy against them. The safety concern of these vaccines is also discussed. It is important to understand how coronavirus gets mutated to design better new vaccines, providing long-term protection and neutralizing broad mutant variants. A proper study approach also needs to be considered while designing the vaccine efficacy trials, which further improved the study outcomes. Taking preventive measures to protect from the virus is also equally important, like vaccine development.

Quantifying Efficiency Gains of Innovative Designs of Two-Arm Vaccine Trials for COVID-19 Using an Epidemic Simulation Model

Clinical trials of a vaccine during an epidemic face particular challenges, such as the pressure to identify an effective vaccine quickly to control the epidemic, and the effect that time-space-varying infection incidence has on the power of a trial. We illustrate how the operating characteristics of different trial design elements maybe evaluated using a network epidemic and trial simulation model, based on COVID-19 and individually randomized two-arm trials with a binary outcome. We show that "ring" recruitment strategies, prioritizing participants at an imminent risk of infection, can result in substantial improvement in terms of power in the model we present. In addition, we introduce a novel method to make more efficient use of the data from the earliest cases of infection observed in the trial, whose infection may have been too early to be vaccine-preventable. Finally, we compare several methods of response-adaptive randomization (RAR), discussing their advantages and disadvantages in the context of our model and identifying particular adaptation strategies that preserve power and estimation properties, while slightly reducing the number of infections, given an effective vaccine.

Recommendations for acceleration of vaccine development and emergency use filings for COVID-19 leveraging lessons from the novel oral polio vaccine

A new oral polio vaccine, nOPV2, has become the first vaccine to pursue a WHO Emergency Use Listing. Many lessons were learned as part of the accelerated development plan and submission, which have been categorized under the following sections: regulatory, clinical development, chemistry manufacturing and controls, and post-deployment monitoring. Efforts were made to adapt findings from these studies to COVID-19 vaccine candidates. Specific concepts for accelerating COVID-19 vaccine development across multiple functional domains were also included. The goals of this effort were twofold: (1) to help familiarize vaccine developers with the EUL process; and (2) to provide general guidance for faster development and preparations for launch during the COVID-19 pandemic.

Evaluating the Long-Term Efficacy of COVID-19 Vaccines

Large-scale deployment of safe and durably effective vaccines can curtail the COVID-19 pandemic. ^1-3 However, the high vaccine efficacy (VE) reported by ongoing phase 3 placebo-controlled clinical trials is based on a median follow-up time of only about two months ^4-5 and thus does not pertain to long-term efficacy. To evaluate the duration of protection while allowing trial participants timely access to efficacious vaccine, investigators can sequentially cross participants over from the placebo arm to the vaccine arm according to priority groups. Here, we show how to estimate potentially time-varying placebo-controlled VE in this type of staggered vaccination of participants. In addition, we compare the performance of blinded and unblinded crossover designs in estimating long-term VE.

Authors’ Information

Dan-Yu Lin, Ph.D., is Dennis Gillings Distinguished Professor of Biostatistics, and Donglin Zeng, Ph.D., is Professor of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599-7420, USA. Peter B. Gilbert, Ph.D., is Member, Vaccine and Infectious Disease Division, Fred Hutch, Seattle, WA 98109-1024, USA.

Summary

We show how to estimate the potentially waning long-term efficacy of COVID-19 vaccines using data from randomized, placebo-controlled clinical trials with staggered enrollment of participants and sequential crossover of placebo recipients.

Evaluating Use Cases for Human Challenge Trials in Accelerating SARS-CoV-2 Vaccine Development

Human challenge trials (HCTs) have been proposed as a means to accelerate SARS-CoV-2 vaccine development. We identify and discuss three potential use cases of HCTs in the current pandemic: evaluating efficacy, converging on correlates of protection, and improving understanding of pathogenesis and the human immune response. We outline the limitations of HCTs and find that HCTs are likely to be most useful for vaccine candidates currently in preclinical stages of development. We conclude that, while currently limited in their application, there are scenarios in which HCTs would be extremely beneficial. Therefore, the option of conducting HCTs to accelerate SARS-CoV-2 vaccine development should be preserved. As HCTs require many months of preparation, we recommend an immediate effort to (1) establish guidelines for HCTs for COVID-19; (2) take the first steps toward HCTs, including preparing challenge virus and making preliminary logistical arrangements; and (3) commit to periodically re-evaluating the utility of HCTs.

Vaccine Development: From Laboratory to Policy

Vaccines are one of the greatest public health achievements, protecting children and adults against numerous infectious diseases; however, the complex, rigorous process of vaccine development is unknown to many. A candidate vaccine undergoes extensive evaluation of safety and efficacy to meet licensure requirements before recommendations for use become policy. This time-consuming process involves an intricate collaboration among academia, public and private organizations, and federal agencies to ensure that safety is prioritized in every step. Vaccine safety continues to be monitored after licensure through a robust system. Yet, vaccine hesitancy remains a major challenge, especially now with the coronavirus disease 2019 (COVID-19) pandemic and concerns about the speed with which candidate vaccines are being developed. This article reviews the vaccine development process and the systems in place to ensure safety and effectiveness. A better understanding of these topics is necessary to address concerns and improve public acceptance of all vaccines, particularly COVID-19 vaccines. [Pediatr Ann. 2020;49(12):e509-e515.].

Current advances in HIV vaccine preclinical studies using Macaque models

The macaque simian or simian/human immunodeficiency virus (SIV/SHIV) challenge model has been widely used to inform and guide human vaccine trials. Substantial advances have been made recently in the application of repeated-low-dose challenge (RLD) approach to assess SIV/SHIV vaccine efficacies (VE). Some candidate HIV vaccines have shown protective effects in preclinical studies using the macaque SIV/SHIV model but the model's true predictive value for screening potential HIV vaccine candidates needs to be evaluated further. Here, we review key parameters used in the RLD approach and discuss their relevance for evaluating VE to improve preclinical studies of candidate HIV vaccines.

An agent-based model of dengue virus transmission shows how uncertainty about breakthrough infections influences vaccination impact projections

Prophylactic vaccination is a powerful tool for reducing the burden of infectious diseases, due to a combination of direct protection of vaccinees and indirect protection of others via herd immunity. Computational models play an important role in devising strategies for vaccination by making projections of its impacts on public health. Such projections are subject to uncertainty about numerous factors, however. For example, many vaccine efficacy trials focus on measuring protection against disease rather than protection against infection, leaving the extent of breakthrough infections (i.e., disease ameliorated but infection unimpeded) among vaccinees unknown. Our goal in this study was to quantify the extent to which uncertainty about breakthrough infections results in uncertainty about vaccination impact, with a focus on vaccines for dengue. To realistically account for the many forms of heterogeneity in dengue virus (DENV) transmission, which could have implications for the dynamics of indirect protection, we used a stochastic, agent-based model for DENV transmission informed by more than a decade of empirical studies in the city of Iquitos, Peru. Following 20 years of routine vaccination of nine-year-old children at 80% coverage, projections of the proportion of disease episodes averted varied by a factor of 1.76 (95% CI: 1.54-2.06) across the range of uncertainty about breakthrough infections. This was equivalent to the range of vaccination impact projected across a range of uncertainty about vaccine efficacy of 0.268 (95% CI: 0.210-0.329). Until uncertainty about breakthrough infections can be addressed empirically, our results demonstrate the importance of accounting for it in models of vaccination impact.

Needle size for vaccination procedures in children and adolescents

BACKGROUND

This is an update of a Cochrane Review first published in 2015. The conclusions have not changed.Hypodermic needles of different sizes (gauges and lengths) can be used for vaccination procedures. The gauge (G) refers to the outside diameter of the needle tubing. The higher the gauge number, the smaller the diameter of the needle (e.g. a 23 G needle is 0.6 mm in diameter, whereas a 25 G needle is 0.5 mm in diameter). Many vaccines are recommended for injection into muscle (intramuscularly), although some are delivered subcutaneously (under the skin) and intradermally (into skin). Choosing an appropriate length and gauge of a needle may be important to ensure that a vaccine is delivered to the appropriate site and produces the maximum immune response while causing the least possible harm. Guidelines conflict regarding the sizes of needles that should be used for vaccinating children and adolescents.

OBJECTIVES

To assess the effects of using needles of different sizes for administering vaccines to children and adolescents on vaccine immunogenicity (the ability of the vaccine to elicit an immune response), procedural pain, and other reactogenicity events (adverse events following vaccine administration).

SEARCH METHODS

We updated our searches of CENTRAL, MEDLINE, Embase, and CINAHL to October 2017. We also searched proceedings of vaccine conferences and two trials registers.

SELECTION CRITERIA

Randomised controlled trials evaluating the effects of using hypodermic needles of any gauge or length to administer any type of vaccine to people aged from birth to 24 years.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted trial data and assessed the risk of bias. We contacted trial authors for additional information. We rated the quality of evidence using the GRADE system.

MAIN RESULTS

We included five trials involving 1350 participants in the original review. The updated review identified no new trials. The evidence from two small trials (one trial including infants and one including adolescents) was insufficient to allow any definitive statements to be made about the effects of the needles evaluated in the trials on vaccine immunogenicity and reactogenicity.The remaining three trials (1135 participants) contributed data to comparisons between 25 G 25 mm, 23 G 25 mm, and 25 G 16 mm needles. These trials included infants predominantly aged from two to six months undergoing intramuscular vaccination in the anterolateral thigh using the World Health Organization (WHO) injection technique (skin stretched flat, needle inserted at a 90° angle and up to the needle hub in healthy infants). The vaccines administered were combination vaccines containing diphtheria, tetanus, and whole-cell pertussis antigens (DTwP). In some trials, the vaccines also contained Haemophilus influenzae type b (DTwP-Hib) and hepatitis B (DTwP-Hib-Hep B) antigen components.Primary outcomesIncidence of vaccine-preventable diseases: No trials reported this outcome.Procedural pain and crying: Using a wider gauge 23 G 25 mm needle may slightly reduce procedural pain (low-quality evidence) and probably leads to a slight reduction in the duration of crying time immediately after vaccination (moderate-quality evidence) compared with a narrower gauge 25 G 25 mm needle (one trial, 320 participants). The effects are probably not large enough to be clinically relevant.Secondary outcomesImmune response: There is probably little or no difference in immune response, defined in terms of the proportion of seroprotected infants, between use of 25 G 25 mm, 23 G 25 mm, or 25 G 16 mm needles to administer a series of three doses of a DTwP-Hib vaccine at ages two, three, and four months (moderate-quality evidence, one trial, numbers of participants in analyses range from 309 to 402. The immune response to the pertussis antigen was not measured).Severe and non-severe local reactions: 25 mm needles (either 25 G or 23 G) probably lead to fewer severe and non-severe local reactions after DTwP-Hib vaccination compared with 25 G 16 mm needles (moderate-quality evidence, one trial, 447 to 458 participants in analyses). We estimate that one fewer infant will experience a severe local reaction (extensive redness and swelling) after the first vaccine dose for every 25 infants vaccinated with the longer rather than the shorter needle (number needed to treat for an additional beneficial outcome (NNTB) with a 25 G 25 mm needle: 25 (95% confidence interval (CI) 15 to 100); NNTB with a 23 G 25 mm needle: 25 (95% CI 17 to 100)). We estimate that one fewer infant will experience a non-severe local reaction (any redness, swelling, tenderness, or hardness (composite outcome)) at 24 hours after the first vaccine dose for every 5 or 6 infants vaccinated with a 25 mm rather than a 16 mm needle (NNTB with a 25 G 25 mm needle: 5 (95% CI 4 to 10); NNTB with a 23 G 25 mm needle: 6 (95% CI 4 to 13)). The results are similar after the second and third vaccine doses.Using a narrow gauge 25 G 25 mm needle may produce a small reduction in the incidence of local reactions after each dose of a DTwP vaccine compared with a wider gauge 23 G 25 mm needle, but the effect estimates are imprecise (low-quality evidence, two trials, 100 to 459 participants in analyses).Systemic reactions: The comparative effects of 23 G 25 mm, 25 G 25 mm, and 25 G 16 mm needles on the incidence of postvaccination fever and other systemic events such as drowsiness, loss of appetite, and vomiting are uncertain due to the very low quality of the evidence.

AUTHORS' CONCLUSIONS

Using 25 mm needles (either 23 G or 25 G) for intramuscular vaccination procedures in the anterolateral thigh of infants using the WHO injection technique probably reduces the occurrence of local reactions while achieving a comparable immune response to 25 G 16 mm needles. These findings are applicable to healthy infants aged two to six months receiving combination DTwP vaccines with a reactogenic whole-cell pertussis antigen component. These vaccines are predominantly used in low- and middle-income countries. The applicability of the findings to vaccines with acellular pertussis components and other vaccines with different reactogenicity profiles is uncertain.

The clinical development process for a novel preventive vaccine: An overview

Each novel vaccine candidate needs to be evaluated for safety, immunogenicity, and protective efficacy in humans before it is licensed for use. After initial safety evaluation in healthy adults, each vaccine candidate follows a unique development path. This article on clinical development gives an overview on the development path based on the expectations of various guidelines issued by the World Health Organization (WHO), the European Medicines Agency (EMA), and the United States Food and Drug Administration (USFDA). The manuscript describes the objectives, study populations, study designs, study site, and outcome(s) of each phase (Phase I-III) of a clinical trial. Examples from the clinical development of a malaria vaccine candidate, a rotavirus vaccine, and two vaccines approved for human papillomavirus (HPV) have also been discussed. The article also tabulates relevant guidelines, which can be referred to while drafting the development path of a novel vaccine candidate.

Needle size for vaccination procedures in children and adolescents

BACKGROUND

Hypodermic needles of different sizes (gauges and lengths) can be used for vaccination procedures. The gauge (G) refers to the outside diameter of the needle tubing. The higher the gauge number, the smaller diameter of the needle (eg a 25 G needle is 0.5 mm in diameter and is narrower than a 23 G needle (0.6 mm)). Many vaccines are recommended for injection into muscle (intramuscularly), although some are delivered subcutaneously (under the skin) and intradermally (into skin). Choosing an appropriate length and gauge of a needle may be important to ensure that a vaccine is delivered to the appropriate site and produces the maximum immune response while causing the least possible harm. There are some conflicting guidelines regarding the lengths and gauges of needles that should be used for vaccination procedures in children and adolescents.

OBJECTIVES

To assess the effects of using needles of different lengths and gauges for administering vaccines to children and adolescents on vaccine immunogenicity (the ability of the vaccine to elicit an immune response), procedural pain, and other reactogenicity events (adverse events following vaccine administration).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2014, Issue 10), MEDLINE and MEDLINE in Progress via Ovid (1947 to November 2014), EMBASE via Ovid (1974 to November 2014), and CINAHL via EBSCOhost (1982 to November 2014). We also searched reference lists of articles and textbooks, the proceedings of vaccine conferences, and three clinical trial registers.

SELECTION CRITERIA

Randomised controlled trials evaluating the effects of using hypodermic needles of any gauge or length to administer any type of vaccine to people aged from birth to 24 years.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted trial data and assessed the risk of bias. We contacted trial authors for additional information. We rated the quality of evidence using the GRADE system.

MAIN RESULTS

We included five trials involving 1350 participants. Data for the primary review outcomes were either absent (for the incidence of vaccine-preventable diseases) or limited (for procedural pain and crying). The available evidence was compromised by the use of surrogate immunogenicity outcomes, incomplete blinding of outcome assessors, and imprecision for some outcomes. The evidence from two small trials was insufficient to allow any confident statements to be made about the effects of the needles evaluated in the trials on vaccine immunogenicity and reactogenicity.The remaining three trials (1135 participants) contributed data to comparisons between 25 G 25 mm, 23 G 25 mm, and 25 G 16 mm needles. These trials involved infants predominantly aged two to six months undergoing intramuscular vaccination in the anterolateral thigh using the World Health Organization (WHO) injection technique (skin stretched flat, needle inserted at a 90° angle and up to the needle hub in healthy infants). The vaccines administered were combination vaccines containing diphtheria, tetanus, and whole-cell pertussis antigens (DTwP). In some trials, the vaccines also contained Haemophilus influenzae type b (DTwP-Hib) and hepatitis B (DTwP-Hib-HepB) antigen components.We found moderate quality evidence from one trial that there is probably little or no difference in immune response, defined in terms of the proportion of seroprotected infants, between using 25 G 25 mm, 23 G 25 mm, or 25 G 16 mm needles to administer a series of three doses of a DTwP-Hib vaccine at ages two, three, and four months (numbers of participants in analyses range from 309 to 402. Immune response to pertussis antigen not measured).25 mm needles (either 23 G or 25 G) probably lead to fewer severe local reactions (extensive redness and swelling) and fewer non-severe local reactions (any redness, swelling, tenderness or hardness (composite outcome)) after DTwP-Hib vaccination compared with 25 G 16 mm needles. We estimate that one fewer infant will experience a severe local reaction after the first vaccine dose for every 25 infants vaccinated with the longer rather than the shorter needle (number needed to treat (NNT) 25 (95% confidence interval (CI) 15 to 100)). We estimate that one fewer infant will experience a non-severe local reaction at 24 hours after the first, second, and third vaccine doses for every five to eight infants vaccinated with the longer rather than the shorter needle (NNTs range from 5 (95% CI 4 to 10) to 8 (95% CI 5 to 34)) (moderate quality evidence, one trial for first and second doses, two trials for third dose, numbers of participants in analyses range from 413 to 528).Using a wider gauge needle (23 G 25 mm) may slightly reduce procedural pain (low quality evidence) and probably leads to a slight reduction in the duration of crying time immediately after vaccination (moderate quality evidence) compared with a narrower gauge (25 G 25 mm) needle (one trial, 320 participants). The effects are probably not large enough to be of any clinical relevance. The 25 G 25 mm needle may produce a small reduction in the incidence of local reactions after each dose of a DTwP vaccine compared with the 23 G 25 mm needle, but the effect estimates are imprecise (low quality evidence, two trials, numbers of participants in analyses range from 100 to 459).The comparative effects of 23 G 25 mm, 25 G 25 mm, and 25 G 16 mm needles on the incidence of post-vaccination fever, persistent inconsolable crying, and other systemic events such as drowsiness, loss of appetite, and vomiting are uncertain due to the very low quality of the evidence.

AUTHORS' CONCLUSIONS

Using 25 mm needles (either 23 G or 25 G) for intramuscular vaccination procedures in the anterolateral thigh of infants using the WHO injection technique probably reduces the occurrence of local reactions while achieving a comparable immune response to 25 G 16 mm needles. These findings are applicable to healthy infants aged two to six months receiving combination DTwP vaccines with a reactogenic whole-cell pertussis antigen component. These vaccines are predominantly used in developing countries. The applicability of the findings to vaccines with acellular pertussis components and other vaccines with different reactogenicity profiles is uncertain.

RTS,S vaccination is associated with serologic evidence of decreased exposure to Plasmodium falciparum liver- and blood-stage parasites

The leading malaria vaccine candidate, RTS,S, targets the sporozoite and liver stages of the Plasmodium falciparum life cycle, yet it provides partial protection against disease associated with the subsequent blood stage of infection. Antibodies against the vaccine target, the circumsporozoite protein, have not shown sufficient correlation with risk of clinical malaria to serve as a surrogate for protection. The mechanism by which a vaccine that targets the asymptomatic sporozoite and liver stages protects against disease caused by blood-stage parasites remains unclear. We hypothesized that vaccination with RTS,S protects from blood-stage disease by reducing the number of parasites emerging from the liver, leading to prolonged exposure to subclinical levels of blood-stage parasites that go undetected and untreated, which in turn boosts pre-existing antibody-mediated blood-stage immunity. To test this hypothesis, we compared antibody responses to 824 P. falciparum antigens by protein array in Mozambican children 6 months after receiving a full course of RTS,S (n = 291) versus comparator vaccine (n = 297) in a Phase IIb trial. Moreover, we used a nested case-control design to compare antibody responses of children who did or did not experience febrile malaria. Unexpectedly, we found that the breadth and magnitude of the antibody response to both liver and asexual blood-stage antigens was significantly lower in RTS,S vaccinees, with the exception of only four antigens, including the RTS,S circumsporozoite antigen. Contrary to our initial hypothesis, these findings suggest that RTS,S confers protection against clinical malaria by blocking sporozoite invasion of hepatocytes, thereby reducing exposure to the blood-stage parasites that cause disease. We also found that antibody profiles 6 months after vaccination did not distinguish protected and susceptible children during the subsequent 12-month follow-up period but were strongly associated with exposure. Together, these data provide insight into the mechanism by which RTS,S protects from malaria.

Consensus statement on diagnostic end points for infant tuberculosis vaccine trials

BACKGROUND

 Definition of clinical trial end points for childhood tuberculosis is hindered by lack of a standard case definition. We aimed to identify areas of consensus or debate on potential end points for tuberculosis vaccine trials among human immunodeficiency virus-uninfected children.

METHODS

 Thirty-eight opinion leaders participated in a Consensus Workshop at the Second Global Forum on TB Vaccines (Estonia, 2010). Outcomes were categorized as unanimity, modified consensus, or lack of consensus. Individual reservations were noted.

RESULTS

 Modified consensus was achieved on 3 issues: (1) unsuitability of historical BCG trial end points as sole primary end points for modern infant trials; (2) symptomatic, complicated intrathoracic tuberculosis as an uncommon but clinically relevant disease phenotype; (3) primary complex tuberculosis in younger children as a common, high-risk phenotype, with a high rate of spontaneous resolution. Participants agreed that radiologic diagnosis of intrathoracic tuberculosis would be based primarily on hilar lymphadenopathy. Lack of consensus was noted for (1) significance of isolated culture of Mycobacterium tuberculosis and (2) the need for evidence of prior tuberculosis exposure to support a diagnosis of tuberculosis disease. Reservations were expressed regarding use of interferon-γ release assays and the clinical relevance, and potential for misclassification, of primary complex tuberculosis.

CONCLUSIONS

 The Workshop did not achieve consensus on a single primary end-point definition. Tuberculosis disease phenotypes with optimal diagnostic certainty will be uncommon in the study population. Criteria for composite or multiple end points were identified, and we propose a hierarchy of end-point criteria, based on rate of occurrence, clinical relevance, and diagnostic certainty.

Evaluating the efficacy of a malaria vaccine

Malaria is a major public health problem. An effective vaccine against malaria is actively being sought. We formulate a potential outcomes definition of the efficacy of a malaria vaccine for preventing fever. A challenge in estimating this efficacy is that there is no sure way to determine whether a fever was caused by malaria. We study the properties of two approaches for estimating efficacy: (1) use a deterministic case definition of a malaria caused fever as the conjunction of fever and parasite density above a certain cutoff; (2) use a probabilistic case definition in which the probability that each fever was caused by malaria is estimated. We compare these approaches in a simulation study and find that both approaches can potentially have large biases. We suggest a strategy for choosing an estimator based on the investigator's prior knowledge about the area in which the trial is being conducted and the range of vaccine efficacies over which the investigator would like the estimator to have good properties.

Probing the possibilities for T-cell-based AIDS vaccines

PURPOSE OF REVIEW

This review will discuss the current challenges facing the development of a successful AIDS vaccine and approaches being pursued to overcome them, with an emphasis on vaccines designed to elicit primarily cellular, rather than humoral, antiviral immune responses.

RECENT FINDINGS

Recent insights into the biology of mucosal virus transmission, CD4 T-cell depletion dynamics, the character of virus-specific CD8 T-cell responses, and the dynamic effects that CD8 T cells exert on virus evolution and genetic diversity manifest during lentivirus infections have engendered an improved understanding of the anatomical, physiological, and immunological aspects of HIV infection. These advances help frame the key scientific hurdles to development of a safe and effective AIDS vaccine that an expanding number and diversity of experimental approaches in vaccine design, administration, and evaluation are now seeking to overcome.

SUMMARY

The development of an effective AIDS vaccine remains elusive. Our increasing knowledge regarding the biology of HIV infection, mechanisms of AIDS pathogenesis, and correlates of protective immunity, however, suggest new hypotheses which, when critically evaluated, should bring us closer to the realization of an AIDS vaccine - or at least an improved understanding of the true nature and magnitude of the obstacles ahead.

Uncertainties and anxieties about vaccination, answering parent's concerns

Vaccination is one of the most significant public health interventions responsible for saving millions of lives and preventing significant morbidity. Despite this, there remain concerns about a number of vaccines. Although vaccines are extensively tested, there are genuine questions that many parents have about a number of vaccine-related issues. It is important that practitioners can discuss these concerns because denying or dismissing them may lead parents and patients to seek advice from uninformed sources. This article discusses some of the major concerns about vaccines, including their safety, immunogenicity, and the development of national immunization programs. It concludes that although vaccines are overwhelmingly safe, constant vigilance is required.

A new endpoint definition improved clinical relevance and statistical power in a vaccine trial

OBJECTIVE

Endpoints used for the evaluation of immunogenicity in vaccine trials are often the proportion of individuals with immune response or geometric means of antibody concentrations for each serotype. When a vaccine includes several types of the same species, we illustrate how an endpoint combining all responses may improve clinical relevance and statistical power.

STUDY DESIGN AND SETTINGS

The motivating example was the ANRS 114 Pneumovac trial where the effect of two vaccine strategies against Streptococcus pneumoniae was assessed in adults infected by the Human Immunodeficiency Virus. The power associated with several endpoints was calculated in the example and in simulations. A new endpoint based on four ordered levels is formulated and analyzed by using a proportional odds model.

RESULTS AND CONCLUSION

The analysis of this new endpoint led to an odds ratio allowing detection of improvement and detriment. In the simulation study, this endpoint was associated with the largest statistical power by increasing the amount of information used as compared with usual endpoints. We recommend this new endpoint formulation in the formal development of a new vaccination regimen, whenever applicable.

"Guidelines for the clinical evaluation of dengue vaccines in endemic areas": summary of a World Health Organization Technical Consultation

There is a pressing need for guidelines focused on the clinical evaluation of dengue vaccines in exposed populations, because Phase 1 and 2 clinical trials of dengue vaccines have begun, and Phase 3 field trials may be warranted soon. In response to this need, the WHO Initiative for Vaccine Research (IVR) has conducted a series of expert consultations resulting in guidelines published as a WHO; 2008[Report No.: WHO/IVB/08.12]. This document, directed toward national regulatory authorities (NRAs), vaccine developers and the scientific community at large, provides guidance for the evaluation and registration of dengue vaccines in dengue-endemic countries. The new document builds on a previous guidance document published in 2002 [WHO. Guidelines for the evaluation of dengue vaccines in populations exposed to natural infection. Geneva, Switzerland: WHO; 2002 [Report No.: TDR/IVR/DEN/02.1]]. This report summarizes the recommendations in the new guidelines, which emphasize the many unique aspects of dengue vaccine trials. These include strong recommendations to collect accurate dengue incidence data across multiple transmission seasons, and to conduct Phase 2 or 3 bridging studies, post-Phase 3 follow-up safety studies and Phase 4 post-licensure trials to better elucidate vaccine immunogenicity, protective efficacy, or safety in endemic areas where multiple dengue types and other flaviviruses circulate and where flavivirus vaccines are widely used.

MODELING A FIELD TRIAL OF THE RTS,S/AS02A MALARIA VACCINE

A double-blind, phase IIb, randomized controlled trial of the malaria vaccine RTS,S/AS02A showed an efficacy of 45.0% in reducing the force of infection for Plasmodium falciparum and of 29.9% in reducing incidence of clinical malaria in children 1-4 years of age in Manhiça, Mozambique. We simulate this trial using a stochastic model of P. falciparum epidemiology, and the setting-specific seasonal pattern of entomologic inoculations as input. The simulated incidence curve for the control group was comparable with that observed in the trial. To reproduce the observed efficacy in extending time to first infection, the model needed to assume an efficacy of 52% in reducing the force of infection. This bias arises as a result of acquired partial immunity against blood stages, thus suggesting an explanation for the lower efficacy observed in a previous trial in semi-immune adult men in The Gambia. The shape of the incidence of infection curve for the vaccine cohort in Manhiça indicates that the vaccine provides incomplete protection to a large proportion of the vaccinees, rather than offering complete protection to some recipients and none to others. This behavior is compatible with a model of no decay in efficacy over the six-month surveillance period of the trial. The model accurately reproduced the lower efficacy against clinical disease than against infection. In the simulations this finding resulted from loss of acquired clinical immunity as a result of a reduction in the force of infection in the vaccinated cohort. The model also predicted greater efficacy against severe diseases than against clinical disease. The success of the simulation model in reproducing the results of the Manhiça trial encourages us to apply the same model to predict the potential public health and economic impact if RTS,S/AS02A were to be introduced into the existing expanded program on immunization.

Statistical evaluation of HIV vaccines in early clinical trials

The HIV pandemic is a pressing threat to global public health; HIV vaccine development is critical. Clinical evaluation of HIV vaccine candidates differs from the standard therapeutics trial framework primarily due to the fact that healthy individuals are studied. We present an early stage evaluation program developed for the HIV Vaccine Trials Network (HVTN) motivated by characteristics unique to the vaccine setting. The program consists of 3 prototypical stages (Phase I, Ib, II) that provide a unified yet flexible approach to the safety and immunogenicity evaluation of diverse vaccine regimens. The goal of these early trials is to narrow the number of candidate vaccines to the most promising candidates worthy of further study in efficacy trials.

Prospects for an AIDS vaccine: three big questions, no easy answers

The unremitting devastation created by the AIDS pandemic will probably only be controlled when a vaccine is developed that is safe, effective, affordable, and simple enough to permit implementation in developing countries where the impact of AIDS is most severe. Although formidable practical, political, economic, social, and ethical challenges face the AIDS vaccine development effort, the most fundamental challenges now reside at the level of the basic biology of HIV-1 infection and pathogenesis. Of these biological considerations, three questions loom especially large: can we design immunogens that will elicit neutralising antibodies that are reactive against a wide variety of primary HIV isolates; will vaccine-elicited cytotoxic T cells be fundamentally better at controlling HIV-1 replication and ameliorating disease progression than those responses that arise during natural HIV infection; and to what extent will the tremendous global genetic diversity of HIV-1 compromise the breadth of vaccine-elicited protective immunity and the overall effectiveness of an AIDS vaccine? Although these are three exceptionally challenging questions, they are now being approached with clear hypotheses whose testing is being facilitated by an ever-improving array of technologies for vaccine design and immunological characterisation. The extent to which the field of AIDS vaccine research can now come together to answer these questions in the best coordinated, most efficient manner will probably be an important determinant of how and when an effective AIDS vaccine will be developed.