Immunisation with the BCG and DTPw vaccines induces different programs of trained immunity in mice

In addition to providing pathogen-specific immunity, vaccines can also confer nonspecific effects (NSEs) on mortality and morbidity unrelated to the targeted disease. Immunisation with live vaccines, such as the BCG vaccine, has generally been associated with significantly reduced all-cause infant mortality. In contrast, some inactivated vaccines, such as the diphtheria, tetanus, whole-cell pertussis (DTPw) vaccine, have been controversially associated with increased all-cause mortality especially in female infants in high-mortality settings. The NSEs associated with BCG have been attributed, in part, to the induction of trained immunity, an epigenetic and metabolic reprograming of innate immune cells, increasing their responsiveness to subsequent microbial encounters. Whether non-live vaccines such as DTPw induce trained immunity is currently poorly understood. Here, we report that immunisation of mice with DTPw induced a unique program of trained immunity in comparison to BCG immunised mice. Altered monocyte and DC cytokine responses were evident in DTPw immunised mice even months after vaccination. Furthermore, splenic cDCs from DTPw immunised mice had altered chromatin accessibility at loci involved in immunity and metabolism, suggesting that these changes were epigenetically mediated. Interestingly, changing the order in which the BCG and DTPw vaccines were co-administered to mice altered subsequent trained immune responses. Given these differences in trained immunity, we also assessed whether administration of these vaccines altered susceptibility to sepsis in two different mouse models. Immunisation with either BCG or a DTPw-containing vaccine prior to the induction of sepsis did not significantly alter survival. Further studies are now needed to more fully investigate the potential consequences of DTPw induced trained immunity in different contexts and to assess whether other non-live vaccines also induce similar changes.     

A place for neutrophils in the beneficial pathogen-agnostic effects of the BCG vaccine

The BCG vaccine has long been recognized for reducing the risk to suffer from infectious diseases unrelated to its target disease, tuberculosis. Evidence from human trials demonstrate substantial reductions in all-cause mortality, especially in the first week of life. Observational studies have identified an association between BCG vaccination and reduced risk of respiratory infectious disease and clinical malaria later in childhood. The mechanistic basis for these pathogen-agnostic benefits, also known as beneficial non-specific effects (NSE) of BCG have been attributed to trained immunity, or epigenetic reprogramming of hematopoietic cells that give rise to innate immune cells responding more efficiently to a broad range of pathogens. Furthermore, within trained immunity, the focus so far has been on enhanced monocyte function. However, polymorphonuclear cells, namely neutrophils, are not only major constituents of the hematopoietic compartment but functionally as well as numerically represent a prominent component of the immune system. The beneficial NSEs of the BCG vaccine on newborn sepsis was recently demonstrated to be driven by a BCG-mediated numeric increase of neutrophils (emergency granulopoiesis (EG)). And experimental evidence in animal models suggest that BCG can modulate neutrophil function as well. Together, these findings suggest that neutrophils are crucial to at least the immediate beneficial NSE of the BCG vaccine. Efforts to uncover the full gamut of mechanisms underpinning the broad beneficial effects of BCG should therefore include neutrophils at the forefront.     

One or two doses of hepatitis A vaccine in universal vaccination programs in children in 2020: A systematic review

BackgroundHepatitis A virus (HAV) is a global health concern as outbreaks continue to occur. Since 1999, several countries have introduced universal vaccination (UV) of children against HAV according to approved two-dose schedules. Other countries have implemented one-dose UV programs since 2005; the long-term impact of this schedule is not yet known.MethodsWe conducted a systematic literature search in four electronic databases for data published between January 2000 and July 2019 to assess evidence for one-dose and two-dose UV of children with non-live HAV vaccines and describe their global impact on incidence, mortality, and severity of hepatitis A, vaccine effectiveness, vaccine efficacy, and antibody persistence.ResultsOf 3739 records screened, 33 peer-reviewed articles and one conference abstract were included. Rapid declines in incidence of hepatitis A and related outcomes were observed in all age groups post-introduction of UV programs, which persisted for at least 14 years for two-dose and six years for one-dose programs according to respective study durations. Vaccine effectiveness was ≥95% over 3–5 years for two-dose programs. Vaccine efficacy was >98% over 0.1–7.5 years for one-dose vaccination. Antibody persistence in vaccinated individuals was documented for up to 15 years (≥90%) and ten years (≥74%) for two-dose and one-dose schedules, respectively.ConclusionExperience with two-dose UV of children against HAV is extensive, demonstrating an impact on the incidence of hepatitis A and antibody persistence for at least 15 years in many countries globally. Because evidence is more limited for one-dose UV, we were unable to draw conclusions on immune response persistence beyond ten years or the need for booster doses later in life. Ongoing epidemiological monitoring is essential in countries implementing one-dose UV against HAV. Based on current evidence, two doses of non-live HAV vaccines are needed to ensure long-term protection.     

A systematic review of pneumococcal conjugate vaccine impact on pneumococcal nasopharyngeal colonisation density in children under 5 years of age

BackgroundHigh pneumococcal carriage density has been associated with severe pneumonia in some settings. The impact of pneumococcal conjugate vaccines (PCVs) on pneumococcal carriage density has been variable. The aim of this systematic literature review is to describe the effect of PCV7, PCV10 and PCV13 on pneumococcal colonisation density in children under five years old.MethodsWe included peer reviewed English literature published between 2000 and 2021 to identify relevant articles using Embase, Medline and PubMed. Original research articles of any study design in countries where PCV has been introduced/studied were included. Quality (risk) assessment was performed using tools developed by the National Heart Brain and Lung Institute for inclusion in this review. We used a narrative synthesis to present results.ResultsTen studies were included from 1941 articles reviewed. There were two randomised controlled trials, two cluster randomised trials, one case control study, one retrospective cohort study and four cross sectional studies. Three studies used semiquantitative culture methods to determine density while the remaining studies used quantitative molecular techniques. Three studies reported an increase in density and three studies found a decrease in density among vaccinated compared with unvaccinated children. Four studies found no effect. There was considerable heterogeneity in the study populations, study design and laboratory methods.ConclusionThere was no consensus regarding the impact of PCV on pneumococcal nasopharyngeal density. We recommend the use of standardised methods to evaluate PCV impact on density.     

Barriers to vaccination in Latin America: A systematic literature review

Current vaccination coverage rates in Latin America and the Caribbean (LAC) are lower than the region-wide rates set by the Pan American Health Organization. To improve vaccination uptake, it is crucial to identify barriers to vaccination. We conducted a systematic literature review to identify the key barriers to vaccination in the LAC region, and to classify and quantify factors affecting vaccination coverage using the barrier categories outlined by the Strategic Advisory Group of Experts (SAGE) working group. We mapped knowledge gaps in the understanding of region-specific and population-specific vaccine hesitancy. Nine databases (Medline via PubMed, Web of Science, LILACS, MedCarib, SciELO, Scopus, PATH, SAGE Online and Google Scholar) were searched for articles published in English, Spanish and Portuguese up to 15 July 2017. A total of 6867 articles were identified of which 75 were included in the review. Majority of the articles were quantitative in nature and nearly half from Brazil. Many other countries in LAC have limited published evidence on barriers to vaccination. The most commonly investigated target population was parents (of children <8 years of age [yoa] and adolescents 9–10 yoa) but there was a balance in the number of publications that reported on influenza, childhood and human papillomavirus vaccination. There was limited direct evidence which reported insights on the new generation of childhood vaccines (pneumococcal or meningococcal vaccines) or studies targeting adolescents and pregnant women. Among the SAGE barrier categories, ‘individual/group influences’ were the most frequently reported barrier category (68%) followed by ‘contextual influences’ (47%). Adverse socioeconomic factors, a low level of education, lack of awareness of diseases and their vaccines, religious and cultural beliefs are commonly cited as obstacles to vaccination acceptance. Additional evidence is needed to fully understand the barriers to vaccination for different target populations, countries in the region and specific vaccine types.     

Differences and disparities in seasonal influenza vaccine,acceptance, adverse reactions,and coverage by age,sex, gender,and race

BackgroundInfluenza is a significant threat to public health worldwide. Despite the widespread availability of effective and generally safe vaccines, the acceptance and coverage of influenza vaccines are significantly lower than recommended. Sociodemographic variables are known to be potential predictors of differential influenza vaccine uptake and outcomes.ObjectivesThis review aims to (1) identify how sociodemographic characteristics such as age, sex, gender, and race may influence seasonal influenza vaccine acceptance and coverage; and (2) evaluate the role of these sociodemographic characteristics in differential adverse reactions among vaccinated individuals.MethodsPubMed was used as the database to search for published literature in three thematic areas related to the seasonal influenza vaccine - vaccine acceptance, adverse reactions, and vaccine coverage.ResultsA total of 3249 articles published between 2010 and 2020 were screened and reviewed, of which 39 studies were included in this literature review. By the three thematic areas, 17 studies assessed vaccine acceptance, 8 studies focused on adverse reactions, and 14 examined coverage of the seasonal influenza vaccine. There were also two studies that focused on more than one of the areas of interest.ConclusionEach of the four sociodemographic predictors – age, sex, race, and gender – were found to significantly influence vaccine acceptance, receipt and outcomes in this review.     

Bacille Calmette-Guérin vaccination at birth and differential white blood cell count in infancy. A randomised clinical trial

BackgroundThe Bacille Calmette-Guérin (BCG) vaccine against tuberculosis (TB) may have beneficial non-specific effects (NSEs) beyond the protection against TB. This may be related to modifications of the innate immune system. We investigated the effect of BCG at birth on differential white blood cell (WBC) count in healthy, Danish infants.MethodThe Danish Calmette Study randomised newborns to BCG at birth (Danish strain 1331, Statens Serum Institut) or no intervention. A sub-group of infants had blood samples collected 4 days after randomisation (n = 161), and at age 3 months (n = 152) and 13 months (n = 300). We evaluated the effect of BCG on WBC differential count (total leucocytes, lymphocytes, monocytes, eosinophil, neutrophil and basophil granulocytes (10⁹ cells/L)) measured in peripheral blood.ResultsOverall, we found no effect of BCG on differential WBC counts at any time point.ConclusionBCG at birth did not affect WBC count in our cohort of healthy, Danish infants.     

Efficacy,immunogenicity, and safety of available vaccines in children on biologics: A systematic review and meta-analysis

Vaccinations are essential for preventing infectious diseases in children with chronic diseases as they have increased risk of infection from frequent use of biologics. Response to immunizations in this group is not well known.ObjectiveA systematic review was performed to evaluate three primary outcomes: efficacy; immunogenicity; and safety of vaccines in children with chronic conditions treated with biologics.MethodsThe protocol for our systematic review and meta-analysis was registered and published with PROSPERO. We searched electronic bibliographic databases for studies published from 2009 to 2019, focusing on vaccinations in children with chronic conditions treated with biologics.ResultsWe retrieved 532 records. Thirty-one full-text articles were selected, and 14 were included in the meta-analysis. No significant publication bias was found. Efficacy: limited data are available regarding the efficacy of vaccination, as most studies have focused on immunogenicity as surrogate outcome for efficacy. Immunogenicity: patients receiving anti-TNF-alpha therapy had a statistically significant risk of poor seroconversion (p = 0.028) and seroprotection by the serotype B influenza vaccine [inflammatory bowel disease (IBD) p = 0.013; juvenile idiopathic arthritis (JIA) p = 0.004]. We found adequate responses with H1N1 and H3N2 serotypes. Few studies existed for pneumococcal, hepatitis A virus, hepatitis B virus, varicella-zoster virus, Measles Mumps Rubella virus, and multiple vaccine administration. Safety: vaccine administration was not associated with serious side effects, but JIA patients on anti-TNF alpha therapy had a statistically significant risk of presenting with myalgia or arthralgia postinfluenza vaccine (p = 0.014).ConclusionsMore evidence concerning efficacy, immunogenicity, and safety of vaccinations is needed to guide physicians in the vaccine decision process for this pediatric population.     

Flavivirus vaccines: Virus-like particles and single-round infectious particles as promising alternatives

The genus flavivirus of the Flaviridae family includes several human pathogens, like dengue, Zika, Japanese encephalitis, and yellow fever virus. These viruses continue to be a significant threat to human health. Vaccination remains the most useful approach to reduce the impact of flavivirus fever. However, currently available vaccines can induce severe side effects or have low effectiveness. An alternative is the use of recombinant vaccines, of which virus-like particles (VLP) and single-round infectious particles (SRIP) are of especial interest. VLP consist of the virus structural proteins produced in a heterologous system that self-assemble in a structure almost identical to the native virus. They are highly immunogenic and have been effective vaccines for other viruses for over 30 years. SRIP are promising vaccine candidates, as they induce both cellular and humoral responses, as viral proteins are expressed. Here, the state of the art to produce both types of particles and their use as vaccines against flaviviruses are discussed. We summarize the different approaches used for the design and production of flavivirus VLP and SRIP, the evidence for their safety and efficacy, and the main challenges for their use as commercial vaccines.     

Development of in ovo-compatible NS1-truncated live attenuated influenza vaccines by modulation of hemagglutinin cleavage and polymerase acidic X frameshifting sites

Emerging avian influenza viruses pose a high risk to poultry production, necessitating the need for more broadly protective vaccines. Live attenuated influenza vaccines offer excellent protective efficacies but their use in poultry farms is discouraged due to safety concerns related to emergence of reassortant viruses. Vaccination of chicken embryos inside eggs (in ovo) induces early immunity in young chicks while reduces the safety concerns related to the use of live vaccines on farms. However, in ovo vaccination using influenza viruses severely affects the egg hatchability. We previously engineered a high interferon-inducing live attenuated influenza vaccine candidate with an enhanced protective efficacy in chickens. Here, we asked whether we could further modify this high interferon-inducing vaccine candidate to develop an in ovo-compatible live attenuated influenza vaccine. We first showed that the enhanced interferon responses induced by the vaccine is not enough to attenuate the virus in ovo. To reduce the pathogenicity of the virus for chicken embryos, we replaced the hemagglutinin cleavage site of the H7 vaccine virus (PENPKTR/GL) with that of the H6-subtype viruses (PQIETR/GL) and disrupted the ribosomal frameshifting site responsible for viral polymerase acidic X protein expression. In ovo vaccination of chickens with up to 10⁵ median egg infectious dose of the modified vaccine had minimal effects on hatchability while protecting the chickens against a heterologous challenge virus at two weeks of age. This study demonstrates that targeted genetic mutations can be applied to further attenuate and enhance the safety of live attenuated influenza vaccines to develop future in ovo vaccines for poultry.     

The comparative efficacy and safety of herpes zoster vaccines: A network meta-analysis

BackgroundWe estimated the relative efficacy and safety of vaccines for prevention of herpes zoster (HZ) using network meta-analysis (NMA) based on evidence from randomized controlled trials.MethodsA systematic literature review evaluated two different HZ vaccines: adjuvanted recombinant zoster vaccine (RZV) and zoster vaccine live (ZVL), with different formulations assessed. Detailed feasibility assessment indicated that a NMA was feasible for efficacy (incidence of HZ and postherpetic neuralgia [PHN]) and safety (serious adverse events [SAE] and reactogenicity [injection-site reactions, systemic reaction]) outcomes. Primary analyses included frequentist NMAs with fixed effects for efficacy outcomes, due to limited data availability, and both fixed and random effects for safety and reactogenicity outcomes. As age is a known effect modifier of vaccine efficacy (VE), VE analyses were stratified by age.ResultsRZV demonstrated significantly higher HZ efficacy than ZVL in adults ≥60 years of age (YOA) (VE_RZV = 0.92 (95% confidence interval [95%CI]: 0.88, 0.94), VE_ZVL = 0.51 (95%CI: 0.44, 0.57)) and adults ≥70 YOA (VE_RZV = 0.91 (95%CI: 0.87, 0.94), VE_ZVL = 0.37 (95%CI: 0.25, 0.48)). Similarly, RZV demonstrated significantly higher PHN efficacy than ZVL in adults ≥60 YOA (VE_RZV = 0.89 (95%CI: 0.70, 0.96), VE_ZVL = 0.66 (95%CI: 0.48, 0.78)) and adults ≥70 YOA (VE_RZV = 0.89 (95%CI: 0.69, 0.96), VE_ZVL = 0.67 (95%CI: 0.44, 0.80)). RZV was associated with significantly more injection-site and systemic reactions compared to most formulations of ZVL and placebo, however definitions and data collection procedures differed across the included studies. There were no statistically significant differences found between RZV and any formulation of ZVL or placebo for SAEs.ConclusionRZV is significantly more effective in reducing HZ and PHN incidence in adults ≥60 YOA, compared with ZVL. As anticipated with an adjuvanted vaccine, RZV results in more reactogenicity following immunization. No differences in SAEs were found between RZV and ZVL.     

Meeting Summary: Global Vaccine and Immunization Research Forum, 2021

The 2021 Global Vaccine and Immunization Research Forum highlighted the considerable advances and recent progress in research and development for vaccines and immunization, critically reviewed lessons learned from COVID-19 vaccine programs, and looked ahead to opportunities for this decade.For COVID-19, decades of investments in basic and translational research, new technology platforms, and vaccines targeting prototype pathogens enabled a rapid, global response. Unprecedented global coordination and partnership have played an essential role in creating and delivering COVID-19 vaccines. More improvement is needed in product attributes such as deliverability, and in equitable access to vaccines.Developments in other priority areas included: the halting of two human immunodeficiency virus vaccine trials due to lack of efficacy in preventing infection; promising efficacy results in Phase 2 trials of two tuberculosis vaccines; pilot implementation of the most advanced malaria vaccine candidate in three countries; trials of human papillomavirus vaccines given in single-dose regimens; and emergency use listing of a novel, oral poliomyelitis type 2 vaccine. More systematic, proactive approaches are being developed for fostering vaccine uptake and demand, aligning on priorities for investment by the public and private sectors, and accelerating policy making.Participants emphasized that addressing endemic disease is intertwined with emergency preparedness and pandemic response, so that advances in one area create opportunities in the other. In this decade, advances made in response to the COVID-19 pandemic should accelerate availability of vaccines for other diseases, contribute to preparedness for future pandemics, and help to achieve impact and equity under Immunization Agenda 2030.     

Sensorineural hearing loss (SNHL) as an adverse event following immunization (AEFI): Case definition & guidelines for data collection,analysis, and presentation of immunization safety data

This is a Brighton Collaboration case definition of the term “Sensorineural Hearing Loss” to be utilized in the evaluation of adverse events following immunization. The case definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of vaccines for Lassa Fever and other emerging pathogens. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and define levels of diagnostic certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network.     

Importance and value of adjuvanted influenza vaccine in the care of older adults from a European perspective – A systematic review of recently published literature on real-world data

BackgroundThere is an urgent need for improved influenza vaccines especially for older adults due to the presence of immunosenescence. It is therefore highly relevant to compare enhanced influenza vaccines with traditional influenza vaccines with respect to their effectiveness.ObjectiveTo compare vaccine efficacy and effectiveness of adjuvanted influenza vaccines (aTIV/aQIV) vs. non-adjuvanted standard-dose (TIV/QIV) and high-dose (TIV-HD/QIV-HD) influenza vaccines regarding influenza-related outcomes in older adults, complementing findings from the European Centre for Disease Prevention and Control (ECDC)’s systematic review of enhanced seasonal influenza vaccines from February 2020.MethodsA systematic literature search was conducted in Embase and MEDLINE to identify randomised controlled trials, observational studies and systematic reviews, published since ECDC’s systematic review (between 7 February 2020 and 6 September 2021). Included studies were appraised with either the Cochrane Risk of Bias tool, ROBINS-I or AMSTAR 2.ResultsEleven analyses from nine real-world evidence (RWE) studies comprising ～53 million participants and assessing the relative vaccine effectiveness (rVE) of aTIV vs. TIV, QIV and/or TIV-HD in adults aged ≥65 years over the 2006/07–2008/09 and 2011/12–2019/20 influenza seasons were identified. Nine analyses found that aTIV was significantly more effective than TIV and QIV in reducing influenza-related outcomes by clinical setting and suspected influenza outbreaks (rVE ranging from 7.5% to 25.6% for aTIV vs. TIV and 7.1% to 36.3% for aTIV vs. QIV). Seven analyses found similar effectiveness of aTIV vs. TIV-HD in reducing influenza-related medical encounters, inpatient stays and hospitalisations/emergency room visits. In three analyses, aTIV was significantly more effective than TIV-HD in reducing influenza-related medical encounters and office visits (rVE ranging from 6.6% to 16.6%). Risk of bias of identified studies was moderate to high.ConclusionsOur study suggests that both adjuvanted and high-dose vaccines are effective alternatives for vaccination programmes in older adults and preferable over conventional standard-dose vaccines.     

Variant SARS-CoV-2 mRNA vaccines confer broad neutralization as primary or booster series in mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of a global pandemic. Safe and effective COVID-19 vaccines are now available, including mRNA-1273, which has shown 94% efficacy in prevention of symptomatic COVID-19 disease. However, the emergence of SARS-CoV-2 variants has led to concerns of viral escape from vaccine-induced immunity. Several variants have shown decreased susceptibility to neutralization by vaccine-induced immunity, most notably B.1.351 (Beta), although the overall impact on vaccine efficacy remains to be determined. Here, we present the initial evaluation in mice of 2 updated mRNA vaccines designed to target SARS-CoV-2 variants: (1) monovalent mRNA-1273.351 encodes for the spike protein found in B.1.351 and (2) mRNA-1273.211 comprising a 1:1 mix of mRNA-1273 and mRNA-1273.351. Both vaccines were evaluated as a 2-dose primary series in mice; mRNA-1273.351 was also evaluated as a booster dose in animals previously vaccinated with mRNA-1273. The results demonstrated that a primary vaccination series of mRNA-1273.351 was effective at increasing neutralizing antibody titers against B.1.351, while mRNA-1273.211 was effective at providing broad cross-variant neutralization. A third (booster) dose of mRNA-1273.351 significantly increased both wild-type and B.1.351-specific neutralization titers. Both mRNA-1273.351 and mRNA-1273.211 are being evaluated in pre-clinical challenge and clinical studies.     

Hexavalent vaccines: What can we learn from head-to-head studies?

BackgroundThree hexavalent vaccines against diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B virus (HBV), and Haemophilus influenzae type b (Hib) are licensed in Europe: Infanrix hexa (DT3aP-HBV-IPV/Hib), Hexyon (DT2aP-HBV-IPV-Hib) and Vaxelis (DT5aP-HBV-IPV-Hib).MethodsA systematic literature search was performed in various electronic databases to identify published peer-reviewed head-to-head studies comparing any licensed hexavalent vaccine to another.ResultsPredefined inclusion criteria were met by 12 articles. Individual studies concluded that the 3 hexavalent vaccines have acceptable safety profiles although some significant differences were observed in their reactogenicity profiles. The immunogenicity of DT2aP-HBV-IPV-Hib and DT5aP-HBV-IPV-Hib was non-inferior versus DT3aP-HBV-IPV/Hib. Some differences in immune responses to common antigens were observed, but their clinical relevance was not established. Anti-filamentous hemagglutinin (FHA) from pertussis and anti-polyribosylribitol phosphate (PRP) from Hib antibody concentrations tended to be higher, and anti-HBV and anti-pertussis toxin (PT) from pertussis antibody concentrations lower in DT2aP-HBV-IPV-Hib versus DT3aP-HBV-IPV/Hib vaccinees. Anti-PT and post-primary anti-PRP antibody concentrations tended to be higher, and anti-HBV, anti-FHA, anti-pertactin from pertussis and post-booster anti-PRP antibody concentrations lower in DT5aP-HBV-IPV-Hib versus DT3aP-HBV-IPV/Hib recipients. Slightly lower immune responses towards most vaccine antigens were observed with 2 + 1 versus 3 + 1 schedules post-primary vaccination, suggesting that 2 + 1 schedules should only be considered in countries with very high vaccination coverage.ConclusionAlthough the licensed hexavalent vaccines are generally considered similar, analyses of immunogenicity data from head-to-head trials highlighted differences that could be related to differences in composition and formulation. In addition, the demonstrated non-inferiority of the immunogenicity of the more recent vaccines versus DT3aP-HBV-IPV/Hib does not allow a full bridging to similar efficacy, effectiveness and safety. The availability of DT3aP-HBV-IPV/Hib over > 20 years allowed to collect a wealth of data on its long-term immunogenicity, safety and effectiveness in clinical and post-marketing studies, and makes it a key pillar of pediatric immunization.     

A systematic review and meta-analysis of the effectiveness of LAIV4 and IIV in children aged 6 months to 17 years during the 2016–2017 season

As the real-world effectiveness of quadrivalent live attenuated influenza vaccine (LAIV4) and inactivated influenza vaccine (IIV) has varied in recent seasons, a systematic review and meta-analysis was conducted to more precisely estimate effectiveness in the 2016–2017 season. Relevant studies were identified from a systematic review of published literature and personal communication with study investigators. Five studies conducted in Canada, Finland, Germany, the United Kingdom, and the United States were identified for inclusion. Data were analyzed using a random effects model, with heterogeneity testing and a sensitivity analysis restricted to test-negative case–control studies. Consolidated vaccine effectiveness estimates against all strains were 69% (95% CI: 46 to 82) for LAIV4 and 47% (95% CI: 29 to 61) for IIV. Heterogeneity testing was not statistically significant, indicating consistency of individual study results. In conclusion, LAIV4 and IIV showed moderate and comparable effectiveness against influenza in children during the 2016–2017 influenza season.     

The utilisation of vaccines in humanitarian crises, 2015–2019: A review of practice

BackgroundThe risk factors that emerge with the onset and protraction of humanitarian crises leave populations at a heightened risk of excess morbidity and mortality from vaccine-preventable diseases (VPDs). There is currently little clarity on which vaccines are being used in crises throughout the world, and whether vaccination decisions correspond to local disease threats. This review aimed to collect and analyse such information.MethodsWe reviewed vaccination services from January 2015 to June 2019 across all 25 humanitarian responses that had an activated coordination mechanism during this period. A range of online sources and informants within the humanitarian sector were consulted to compile data on which vaccines were provided in each crisis, and the modality and timing of vaccine provision. The package of vaccination services since the start of each crisis was then compared with local disease burden (baseline + excess due to crisis-emergent risk factors).ResultsThe range of vaccines used in humanitarian crises appears limited. When offered, vaccines were primarily delivered through the pre-existing routine schedule, with few supplementary actions taken in recognition of the need for rapidly enhancing population immunity. Vaccine packages mostly did not address the actual range of VPDs that likely accounted for substantial disease risk.ConclusionsThis review suggests inconsistencies and inequities in vaccine provision to crisis-affected populations. A consistent, standardised and broader approach to vaccine use in crises is needed.     

Meeting report: CEPI consultation on accelerating access to novel vaccines against emerging infectious diseases for pregnant and lactating women,London, 12–13 February 2020

Infectious diseases may cause serious morbidity and mortality in pregnant women, their foetuses, and infants; the risk associated with any newly emerging infectious disease (EID) is likely unknown at the time of its emergence. While the ongoing SARS-CoV-2 pandemic shows that the development of vaccines against new pathogens can be considerably accelerated, the immunization of pregnant women generally lags behind the general population. Guided by the priority pathogen list for WHO’s R&D Blueprint for Action to Prevent Epidemics, this workshop sought to define the evidence needed for use of vaccines against EIDs in pregnant and lactating women, using Lassa fever as a model. Close to 60 maternal immunization (MI) and vaccine safety experts, regulators, vaccine developers, Lassa fever experts, and investigators from Lassa-affected countries examined the critical steps for vaccine development and immunization decisions for pregnant and lactating women. This paper reports on key themes and recommendations from the workshop.Current practice still assumes the exclusion of pregnant women from early vaccine trials. A shift in paradigm is needed to progress towards initial inclusion of pregnant women in Phase 2 and 3 trials. Several practical avenues were delineated. Participants agreed that vaccine platforms should be assessed early for their suitability for maternal immunization. It was noted that, in some cases, nonclinical data derived from assessing a given platform using other antigens may be adequate evidence to proceed to a first clinical evaluation and that concurrence from regulators may be sought with supporting rationale. For clinical trials, essential prerequisites such as documenting the disease burden in pregnant women, study site infrastructure, capabilities, and staff experience were noted. Early and sustained communication with the local community was considered paramount in any program for the conduct of MI trials and planned vaccine introduction.     

Systematic literature review of cross-protective effect of HPV vaccines based on data from randomized clinical trials and real-world evidence

BackgroundThe extent of cross-protection provided by currently licensed bivalent and quadrivalent HPV vaccines versus direct protection against HPV 31-, 33-, 45-, 52-, and 58-related disease is debated. A systematic literature review was conducted to establish the duration and magnitude of cross-protection in interventional and observational studies.MethodsPubMed and Embase databases were searched to identify randomized controlled trials (RCT) and observational studies published between 2008 and 2019 reporting on efficacy and effectiveness of HPV vaccines in women against non-vaccine types 31, 33, 45, 52, 58, and 6 and 11 (non-bivalent types). Key outcomes of interest were vaccine efficacy against 6- and 12-month persistent infection or genital lesions, and type-specific genital HPV prevalence or incidence. RCT data were analyzed for the according-to-protocol (bivalent vaccine) or negative-for-14-HPV-types (quadrivalent vaccine) efficacy cohorts.ResultsData from 23 RCTs and 33 observational studies evaluating cross-protection were extracted. RCTs assessed cross-protection in post-hoc analyses of small size subgroups. Among fully vaccinated, baseline HPV-naïve women, the bivalent vaccine showed statistically significant cross-protective efficacy, although with wide confidence intervals, against 6-month and 12-month persistent cervical infections and CIN2+ only consistently for HPV 31 and 45, with the highest effect observed for HPV 31 (range 64.6% [95% CI: 27.6 to 83.9] to 79.1% [97.7% CI: 27.6 to 95.9] for 6-month persistent infection; maximal follow-up 4.7 years). No cross-protection was shown in extended follow-up. The quadrivalent vaccine efficacy reached statistical significance for HPV 31 (46.2% [15.3–66.4]; follow-up: 3.6 years). Similarly, observational studies found consistently significant effectiveness only against HPV 31 and 45 with both vaccines.ConclusionsRCTs and observational studies show that cross-protection is inconsistent across non-vaccine HPV types and is largely driven by HPV 31 and 45. Furthermore, existing data suggest that it wanes over time; its long-term durability has not been established.