The Strategic Advisory Group of Experts (SAGE) on Immunization-Past, Present and Future.

Background/objectives: In November 1999, WHO established the Strategic Advisory Group of Experts (SAGE) on Immunization as a multidisciplinary group of experts to provide high-level recommendations on vaccines and immunization.

Methods: This review provides an overview of SAGE's work in the past 25 years. It further outlines the processes and methods currently used by SAGE and highlights some of its major achievements.

A Practical Guide to Full Value of Vaccine Assessments.

Articulating the wide range of health, social and economic benefits that vaccines offer may help to overcome obstacles in the vaccine development pipeline. A framework to guide the assessment and communication of the value of a vaccine-the Full Value of Vaccine Assessment (FVVA)-has been developed by the WHO. The FVVA framework offers a holistic assessment of the value of vaccines, providing a synthesis of evidence to inform the public health need of a vaccine, describing the supply and demand aspects, its market and its impact from a health, financial and economic perspective.

Immunogenicity and safety of fractional doses of 17D-213 yellow fever vaccine in children (YEFE): a randomised, double-blind, non-inferiority substudy of a phase 4 trial.

Background: Current supply shortages constrain yellow fever vaccination activities, particularly outbreak response. Although fractional doses of all WHO-prequalified yellow fever vaccines have been shown to be safe and immunogenic in a randomised controlled trial in adults, they have not been evaluated in a randomised controlled trial in young children (9-59 months old). We aimed to assess the immunogenicity and safety of fractional doses compared with standard doses of the WHO-prequalified 17D-213 vaccine in young children.

The future of Japanese encephalitis vaccination: expert recommendations for achieving and maintaining optimal JE control.

Vaccines against Japanese encephalitis (JE) have been available for decades. Currently, most JE-endemic countries have vaccination programs for their at-risk populations. Even so, JE remains the leading recognized cause of viral encephalitis in Asia.

Evidence-informed vaccination decision-making in countries: Progress, challenges and opportunities.

Countries face an increasingly complex vaccination landscape. As well as ever-changing infectious disease epidemiology, the number and diversity of vaccine-preventable diseases, vaccine products, and vaccine technologies continue to increase. To ensure that vaccination decision-making is transparent, country-owned and informed by sound scientific evidence, many countries have established national immunization technical advisory groups (NITAGs) to provide independent expert advice.

Immunogenicity and safety of fractional doses of yellow fever vaccines: a randomised, double-blind, non-inferiority trial.

Background: Stocks of yellow fever vaccine are insufficient to cover exceptional demands for outbreak response. Fractional dosing has shown efficacy, but evidence is limited to the 17DD substrain vaccine. We assessed the immunogenicity and safety of one-fifth fractional dose compared with standard dose of four WHO-prequalified yellow fever vaccines produced from three substrains.

Review of data and knowledge gaps regarding yellow fever vaccine-induced immunity and duration of protection.

Yellow fever (YF) virus is a mosquito-borne flavivirus found in Sub-Saharan Africa and tropical South America. The virus causes YF, a viral hemorrhagic fever, which can be prevented by a live-attenuated vaccine, strain 17D. Despite the vaccine being very successful at decreasing disease risk, YF is considered a re-emerging disease due to the increased numbers of cases in the last 30 years.

Global vaccine action plan lessons learned I: Recommendations for the next decade.

The Global Vaccine Action Plan 2011-2020 (GVAP) was developed to realize the ambitions of the Decade of Vaccines - that all individuals and communities enjoy lives free from vaccine-preventable diseases. It included a comprehensive monitoring and evaluation/accountability framework to assess progress towards global targets with recommendations for corrective actions. While many of the GVAP targets are very unlikely to be met by the end of 2020, substantial progress has nevertheless been made, establishing a strong foundation for a successor global immunization strategy, the Immunization Agenda 2030 (IA2030).

Closer and closer? Maternal immunization: current promise, future horizons.

This state-of-the art manuscript highlights our current understanding of maternal immunization-the practice of vaccinating pregnant women to confer protection on them as well as on their young infants, and thereby reduce vaccine-preventable morbidity and mortality. Advances in our understanding of the immunologic processes that undergird a normal pregnancy, studies from vaccines currently available and recommended for pregnant women, and vaccines for administration in special situations are beginning to build the case for safe scale-up of maternal immunization. In addition to well-known diseases, new diseases are emerging which pose threats.

Estimating the proportion of vaccine-induced hospitalized dengue cases among Dengvaxia vaccinees in the Philippines.

Dengvaxia was used in the Philippines to vaccinate 9-10-year-old school children, living in areas highly endemic for dengue. After about 830,000 had received at least 1 of 3 recommended doses, risks of enhanced disease in dengue-naïve vaccinees were reported. We used Phase 3 trial data to derive the proportions of cases of hospitalised and severe dengue that might have been prevented by the Philippines vaccination programme and, among those cases that may occur in vaccinees, what proportions are likely to arise in those who were seropositive or seronegative for dengue at the time of first vaccination and what proportion in the latter group may be enhanced disease attributable to the vaccine.

Maternal immunization in Malawi: A mixed methods study of community perceptions, programmatic considerations, and recommendations for future planning.

Background: Safe, effective vaccines are given to pregnant women to protect their infants and/or themselves against certain infectious agents; however, apart from tetanus vaccination, maternal immunization in low- and middle-income countries (LMICs) remains low. Tetanus toxoid vaccine is integrated into antenatal care services in Malawi with high coverage and provides an opportunity to identify factors that facilitate successful immunization delivery to pregnant women in LMICs.

Methods: PATH and the University of Malawi's Centre for Social Research conducted a mixed-methods study in 2015 to document community perceptions of maternal immunization, using tetanus vaccine as an example, and to identify factors perceived to be important to successfully introducing other maternal vaccines, such as influenza vaccine, in Malawi.

Differences between coverage of yellow fever vaccine and the first dose of measles-containing vaccine: A desk review of global data sources.

Introduction: The strategy to Eliminate Yellow Fever Epidemics (EYE) is a global initiative that includes all countries with risk of yellow fever (YF) virus transmission. Of these, 40 countries (27 in Africa and 13 in the Americas) are considered high-risk and targeted for interventions to increase coverage of YF vaccine. Even though the World Health Organization (WHO) recommends that YF vaccine be given concurrently with the first dose of measles-containing vaccine (MCV1) in YF-endemic settings, estimated coverage for MCV1 and YF vaccine have varied widely.

Maternal Immunization and Antenatal Care Situation Analysis (MIACSA) study protocol: a multiregional, cross-sectional analysis of maternal immunization delivery strategies to reduce maternal and neonatal morbidity and mortality.

Introduction: Maternal immunization (MI) with tetanus toxoid containing vaccine, is a safe and cost-effective way of preventing neonatal tetanus. Given the prospect of introducing new maternal vaccines in the near future, it is essential to identify and understand current policies, practices and unmet needs for introducing and/or scaling up MI in low-income and middle-income countries (LMICs).

Methods And Analysis: The Maternal Immunization and Antenatal Care Situation Analysis (MIACSA) is a mixed methods, cross-sectional study that will collect data in four phases: (1) a review of global databases for selected health indicators in 136 LMICs; (2) a structured online survey directed at Maternal, Newborn and Child Health and Expanded Programme on Immunization focal points in all 136 LMICs; (3) semistructured telephone interviews of 30 selected LMICs and (4) 10 week-long country visits, including key informant interviews, health facility visits and focus group discussions.

Revised Global Typhoid Vaccination Policy.

Typhoid fever is a continuing public health problem in many low- and middle-income countries; however, routine vaccination as a recommended control strategy has not been implemented in the past in most countries. Greater understanding of the typhoid fever burden, the increasing threat of antimicrobial resistance, and licensure of a new generation of typhoid conjugate vaccines (TCVs) were instrumental in paving the way for the World Health Organization (WHO) to issue a revised global policy on typhoid vaccines in March 2018. The new policy follows evidence-based recommendations by the WHO Strategic Advisory Group of Experts on immunization for routine and catch-up vaccination with TCVs and highlights considerations for universal, risk-based, or phased vaccination strategies in different settings.

Demonstrating vaccine effectiveness during a waning epidemic: A WHO/NIH meeting report on approaches to development and licensure of Zika vaccine candidates.

Since its peak in early 2016, the incidence of Zika virus (ZIKV) cases has declined to such low levels that Phase 3 field efficacy trials may be infeasible. While great progress was made to rapidly advance several vaccine candidates into Phase 1 and 2 clinical trials, in the absence of sustained viral transmission it may be difficult to evaluate the effectiveness of ZIKV vaccine candidates by conducting traditional clinical disease endpoint efficacy studies. However, ZIKV is still circulating at low levels in some areas and is likely to re-emerge in naïve populations or in sites of prior epidemics once population immunity wanes.