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The Cochrane Database of Systematic... May 2018Typhoid fever and paratyphoid fever continue to be important causes of illness and death, particularly among children and adolescents in south-central and southeast... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Typhoid fever and paratyphoid fever continue to be important causes of illness and death, particularly among children and adolescents in south-central and southeast Asia. Two typhoid vaccines are widely available, Ty21a (oral) and Vi polysaccharide (parenteral). Newer typhoid conjugate vaccines are at varying stages of development and use. The World Health Organization has recently recommended a Vi tetanus toxoid (Vi-TT) conjugate vaccine, Typbar-TCV, as the preferred vaccine for all ages.
OBJECTIVES
To assess the effects of vaccines for preventing typhoid fever.
SEARCH METHODS
In February 2018, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, LILACS, and mRCT. We also searched the reference lists of all included trials.
SELECTION CRITERIA
Randomized and quasi-randomized controlled trials (RCTs) comparing typhoid fever vaccines with other typhoid fever vaccines or with an inactive agent (placebo or vaccine for a different disease) in adults and children. Human challenge studies were not eligible.
DATA COLLECTION AND ANALYSIS
Two review authors independently applied inclusion criteria and extracted data, and assessed the certainty of the evidence using the GRADE approach. We computed vaccine efficacy per year of follow-up and cumulative three-year efficacy, stratifying for vaccine type and dose. The outcome addressed was typhoid fever, defined as isolation of Salmonella enterica serovar Typhi in blood. We calculated risk ratios (RRs) and efficacy (1 - RR as a percentage) with 95% confidence intervals (CIs).
MAIN RESULTS
In total, 18 RCTs contributed to the quantitative analysis in this review: 13 evaluated efficacy (Ty21a: 5 trials; Vi polysaccharide: 6 trials; Vi-rEPA: 1 trial; Vi-TT: 1 trial), and 9 reported on adverse events. All trials but one took place in typhoid-endemic countries. There was no information on vaccination in adults aged over 55 years of age, pregnant women, or travellers. Only one trial included data on children under two years of age.Ty21a vaccine (oral vaccine, three doses)A three-dose schedule of Ty21a vaccine probably prevents around half of typhoid cases during the first three years after vaccination (cumulative efficacy 2.5 to 3 years: 50%, 95% CI 35% to 61%, 4 trials, 235,239 participants, moderate-certainty evidence). These data include patients aged 3 to 44 years.Compared with placebo, this vaccine probably does not cause more vomiting, diarrhoea, nausea or abdominal pain (2 trials, 2066 participants; moderate-certainty evidence), headache, or rash (1 trial, 1190 participants; moderate-certainty evidence); however, fever (2 trials, 2066 participants; moderate-certainty evidence) is probably more common following vaccination.Vi polysaccharide vaccine (injection, one dose)A single dose of Vi polysaccharide vaccine prevents around two-thirds of typhoid cases in the first year after vaccination (year 1: 69%, 95% CI 63% to 74%; 3 trials, 99,979 participants; high-certainty evidence). In year 2, trial results were more variable, with the vaccine probably preventing between 45% and 69% of typhoid cases (year 2: 59%, 95% CI 45% to 69%; 4 trials, 194,969 participants; moderate-certainty evidence). These data included participants aged 2 to 55 years of age.The three-year cumulative efficacy of the vaccine may be around 55% (95% CI 30% to 70%; 11,384 participants, 1 trial; low-certainty evidence). These data came from a single trial conducted in South Africa in the 1980s in participants aged 5 to 15 years.Compared with placebo, this vaccine probably did not increase the incidence of fever (3 trials, 132,261 participants; moderate-certainty evidence) or erythema (3 trials, 132,261 participants; low-certainty evidence); however, swelling (3 trials, 1767 participants; moderate-certainty evidence) and pain at the injection site (1 trial, 667 participants; moderate-certainty evidence) were more common in the vaccine group.Vi-rEPA vaccine (two doses)Administration of two doses of the Vi-rEPA vaccine probably prevents between 50% and 96% of typhoid cases during the first two years after vaccination (year 1: 94%, 95% CI 75% to 99%; year 2: 87%, 95% CI 56% to 96%, 1 trial, 12,008 participants; moderate-certainty evidence). These data came from a single trial with children two to five years of age conducted in Vietnam.Compared with placebo, both the first and the second dose of this vaccine increased the risk of fever (1 trial, 12,008 and 11,091 participants, low-certainty evidence) and the second dose increase the incidence of swelling at the injection site (one trial, 11,091 participants, moderate-certainty evidence).Vi-TT vaccine (two doses)We are uncertain of the efficacy of administration of two doses of Vi-TT (PedaTyph) in typhoid cases in children during the first year after vaccination (year 1: 94%, 95% CI -1% to 100%, 1 trial, 1625 participants; very low-certainty evidence). These data come from a single cluster-randomized trial in children aged six months to 12 years and conducted in India. For single dose Vi-TT (Typbar-TCV), we found no efficacy trials evaluating the vaccine with natural exposure.There were no reported serious adverse effects in RCTs of any of the vaccines studied.
AUTHORS' CONCLUSIONS
The licensed Ty21a and Vi polysaccharide vaccines are efficacious in adults and children older than two years in endemic countries. The Vi-rEPA vaccine is just as efficacious, although data is only available for children. The new Vi-TT vaccine (PedaTyph) requires further evaluation to determine if it provides protection against typhoid fever. At the time of writing, there were only efficacy data from a human challenge setting in adults on the Vi-TT vaccine (Tybar), which clearly justify the ongoing field trials to evaluate vaccine efficacy.
Topics: Adolescent; Adult; Child; Child, Preschool; Humans; Incidence; Randomized Controlled Trials as Topic; Salmonella typhi; Time Factors; Typhoid Fever; Typhoid-Paratyphoid Vaccines; Vaccines, Attenuated
PubMed: 29851031
DOI: 10.1002/14651858.CD001261.pub4 -
Human Vaccines & Immunotherapeutics Dec 2024Healthcare workers (HCW) perceptions toward vaccines influence patient and community vaccine decision making. In an era of rising vaccine hesitancy, understanding HCW... (Review)
Review
Healthcare workers (HCW) perceptions toward vaccines influence patient and community vaccine decision making. In an era of rising vaccine hesitancy, understanding HCW vaccine confidence is critical. This systematic review aims to review instruments that have been validated to measure HCW vaccine confidence. We conducted a search in five databases in June 2023. Data was descriptively synthesized. Twelve articles describing 10 different tools were included. Most tools included dimensions or items on vaccine knowledge ( = 9), safety ( = 8), vaccine usefulness ( = 8), recommendation behavior ( = 8), and self-vaccination practice ( = 7). All, except one study, were conducted in high-income countries. There was variability in the quality of the validation process. There is limited existing literature on development and validation of tools for HCW vaccine confidence. Based on the tools currently available, the Pro-VC-Be tool is the most well validated. Further research needs to include low- and middle-income contexts.
Topics: Humans; Vaccines; Vaccination; Databases, Factual; Health Personnel; Income
PubMed: 38506574
DOI: 10.1080/21645515.2024.2322796 -
Journal of Medical Virology Apr 2021The year 2020 started with the emergence of novel coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which causes COVID-19 infection. Soon after...
The year 2020 started with the emergence of novel coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which causes COVID-19 infection. Soon after the first evidence was reported in Wuhan, China, the World Health Organization declared global public health emergency and imminent need to understand the pathogenicity of the virus was required in limited time. Once the genome sequence of the virus was delineated, scientists across the world started working on the development of vaccines. Although, some laboratories have been using previously developed vaccine platforms from severe acute respiratory syndrome coronavirus (SARS) and middle east respiratory syndrome-related coronavirus and apply them in COVID-19 vaccines due to genetic similarities between coronaviruses. We have conducted a literature review to assess the background and current status of COVID-19 vaccines. The worldwide implementation and strategies for COVID-19 vaccine development are summarized from studies reported in years 2015-2020. While discussing the vaccine candidates, we have also explained interpretative immune responses of SARS-CoV-2 infection. There are several vaccine candidates at preclinical and clinical stages; however, only 42 vaccines are under clinical trials. Therefore, more industry collaborations and financial supports to COVID-19 studies are needed for mass-scale vaccine development. To develop effective vaccine platforms against SARS-CoV-2, the genetic resemblance with other coronaviruses are being evaluated which may further promote fast-track trials on previously developed SARS-CoV vaccines.
Topics: COVID-19; COVID-19 Vaccines; Humans; SARS-CoV-2; Vaccines, DNA; Vaccines, Inactivated; Vaccines, Live, Unattenuated; Vaccines, Subunit
PubMed: 33270225
DOI: 10.1002/jmv.26709 -
Vaccines Nov 2021Sex and gender have implications for COVID-19 vaccine efficacy and adverse effects from the vaccine. As vaccination is one of the key responses to the COVID-19 pandemic,... (Review)
Review
Sex and gender have implications for COVID-19 vaccine efficacy and adverse effects from the vaccine. As vaccination is one of the key responses to the COVID-19 pandemic, it is vital that sex and gender differences be acknowledged, measured, and analysed in clinical research. Here, we systematically review published COVID-19 vaccine trials, both interventional and observational, to assess the quality of reporting of sex and gender. Of the 75 clinical trials on COVID-19 vaccines included in this review, only 24% presented their main outcome data disaggregated by sex, and only 13% included any discussion of the implications of their study for women and men. Considering the sex differences in adverse events after vaccination, and the gendered aspects of vaccine hesitancy, these oversights in clinical research on vaccines have implications for recovery from the COVID-19 pandemic and for wider public health.
PubMed: 34835253
DOI: 10.3390/vaccines9111322 -
Vaccine Jan 2023Misinformation and disinformation around vaccines has grown in recent years, exacerbated during the Covid-19 pandemic. Effective strategies for countering vaccine... (Review)
Review
BACKGROUND
Misinformation and disinformation around vaccines has grown in recent years, exacerbated during the Covid-19 pandemic. Effective strategies for countering vaccine misinformation and disinformation are crucial for tackling vaccine hesitancy. We conducted a systematic review to identify and describe communications-based strategies used to prevent and ameliorate the effect of mis- and dis-information on people's attitudes and behaviours surrounding vaccination (objective 1) and examined their effectiveness (objective 2).
METHODS
We searched CINAHL, Web of Science, Scopus, MEDLINE, Embase, PsycInfo and MedRxiv in March 2021. The search strategy was built around three themes(1) communications and media; (2) misinformation; and (3) vaccines. For trials addressing objective 2, risk of bias was assessed using the Cochrane risk of bias in randomized trials tool (RoB2).
RESULTS
Of 2000 identified records, 34 eligible studies addressed objective 1, 29 of which also addressed objective 2 (25 RCTs and 4 before-and-after studies). Nine 'intervention approaches' were identified; most focused on content of the intervention or message (debunking/correctional, informational, use of disease images or other 'scare tactics', use of humour, message intensity, inclusion of misinformation warnings, and communicating weight of evidence), while two focused on delivery of the intervention or message (timing and source). Some strategies, such as scare tactics, appear to be ineffective and may increase misinformation endorsement. Communicating with certainty, rather than acknowledging uncertainty around vaccine efficacy or risks, was also found to backfire. Promising approaches include communicating the weight-of-evidence and scientific consensus around vaccines and related myths, using humour and incorporating warnings about encountering misinformation. Trying to debunk misinformation, informational approaches, and communicating uncertainty had mixed results.
CONCLUSION
This review identifies some promising communication strategies for addressing vaccine misinformation. Interventions should be further evaluated by measuring effects on vaccine uptake, rather than distal outcomes such as knowledge and attitudes, in quasi-experimental and real-life contexts.
Topics: Humans; Pandemics; COVID-19; Vaccines; Vaccination; Communication
PubMed: 36628653
DOI: 10.1016/j.vaccine.2022.12.059 -
The Lancet. Infectious Diseases Aug 2016Influenza vaccine effectiveness (VE) can vary by type and subtype. Over the past decade, the test-negative design has emerged as a valid method for estimation of VE. In... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Influenza vaccine effectiveness (VE) can vary by type and subtype. Over the past decade, the test-negative design has emerged as a valid method for estimation of VE. In this design, VE is calculated as 100% × (1 - odds ratio) for vaccine receipt in influenza cases versus test-negative controls. We did a systematic review and meta-analysis to estimate VE by type and subtype.
METHODS
In this systematic review and meta-analysis, we searched PubMed and Embase from Jan 1, 2004, to March 31, 2015. Test-negative design studies of influenza VE were eligible if they enrolled outpatients on the basis of predefined illness criteria, reported subtype-level VE by season, used PCR to confirm influenza, and adjusted for age. We excluded studies restricted to hospitalised patients or special populations, duplicate reports, interim reports superseded by a final report, studies of live-attenuated vaccine, and studies of prepandemic seasonal vaccine against H1N1pdm09. Two reviewers independently assessed titles and abstracts to identify articles for full review. Discrepancies in inclusion and exclusion criteria and VE estimates were adjudicated by consensus. Outcomes were VE against H3N2, H1N1pdm09, H1N1 (pre-2009), and type B. We calculated pooled VE using a random-effects model.
FINDINGS
We identified 3368 unduplicated publications, selected 142 for full review, and included 56 in the meta-analysis. Pooled VE was 33% (95% CI 26-39; I(2)=44·4) for H3N2, 54% (46-61; I(2)=61·3) for type B, 61% (57-65; I(2)=0·0) for H1N1pdm09, and 67% (29-85; I(2)=57·6) for H1N1; VE was 73% (61-81; I(2)=31·4) for monovalent vaccine against H1N1pdm09. VE against H3N2 for antigenically matched viruses was 33% (22-43; I(2)=56·1) and for variant viruses was 23% (2-40; I(2)=55·6). Among older adults (aged >60 years), pooled VE was 24% (-6 to 45; I(2)=17·6) for H3N2, 63% (33-79; I(2)=0·0) for type B, and 62% (36-78; I(2)=0·0) for H1N1pdm09.
INTERPRETATION
Influenza vaccines provided substantial protection against H1N1pdm09, H1N1 (pre-2009), and type B, and reduced protection against H3N2. Vaccine improvements are needed to generate greater protection against H3N2 than with current vaccines.
FUNDING
None.
Topics: Humans; Influenza A Virus, H1N1 Subtype; Influenza A Virus, H3N2 Subtype; Influenza Vaccines; Influenza, Human; Research Design; Sentinel Surveillance; Vaccination; Vaccine Potency; Vaccines, Attenuated
PubMed: 27061888
DOI: 10.1016/S1473-3099(16)00129-8 -
Vaccines Dec 2020While COVID-19 continues raging worldwide, effective vaccines are highly anticipated. However, vaccine hesitancy is widespread. Survey results on uptake intentions vary... (Review)
Review
While COVID-19 continues raging worldwide, effective vaccines are highly anticipated. However, vaccine hesitancy is widespread. Survey results on uptake intentions vary and continue to change. This review compared trends and synthesized findings in vaccination receptivity over time across US and international polls, assessing survey design influences and evaluating context to inform policies and practices. Data sources included academic literature (PubMed, Embase, and PsycINFO following PRISMA guidelines), news and official reports published by 20 October 2020. Two researchers independently screened potential peer-reviewed articles and syndicated polls for eligibility; 126 studies and surveys were selected. Declining vaccine acceptance (from >70% in March to <50% in October) with demographic, socioeconomic, and partisan divides was observed. Perceived risk, concerns over vaccine safety and effectiveness, doctors' recommendations, and inoculation history were common factors. Impacts of regional infection rates, gender, and personal COVID-19 experience were inconclusive. Unique COVID-19 factors included political party orientation, doubts toward expedited development/approval process, and perceived political interference. Many receptive participants preferred to wait until others have taken the vaccine; mandates could increase resistance. Survey wording and answer options showed influence on responses. To achieve herd immunity, communication campaigns are immediately needed, focusing on transparency and restoring trust in health authorities.
PubMed: 33396832
DOI: 10.3390/vaccines9010016 -
Cureus Sep 2022Dengue is a vector-borne disease caused by the dengue virus (DENV) and is a major health concern worldwide, particularly in regions of endemic disease. Dengue usually... (Review)
Review
Dengue is a vector-borne disease caused by the dengue virus (DENV) and is a major health concern worldwide, particularly in regions of endemic disease. Dengue usually presents as a self-limited febrile illness. In some cases, more severe forms with hemorrhage and shock can occur, and children are especially prone to develop it. These forms can be lethal without appropriate management, and no antiviral treatment exists today. In the absence of a curative treatment for dengue, its clinical prevention remains essential. One vaccine - the chimeric yellow fever-dengue-tetravalent dengue vaccine (CYD-TDV) - has been approved for use in some populations, and several others are currently in development, including Takeda's tetravalent dengue vaccine candidate (TAK-003). This study is a systematic review of the current literature realized to evaluate the efficacy of the dengue vaccines in preventing severe dengue in children. This review focuses on the vaccines CYD-TDV and TAK-003. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, PubMed Central (PMC), Medical Literature Analysis and Retrieval System Online (MEDLINE), Cochrane Library, and Google Scholar were the databases used to find the relevant data. The articles were selected using specific inclusion and exclusion criteria, and quality appraisal was realized with standardized quality assessment tools. Overall, our study shows that the dengue vaccines CYD-TDV and TAK-003 confer protection against severe dengue in children. Some distinctions exist depending on the vaccine type, the age, and the dengue serostatus of patients. While demonstrating encouraging results, this review also emphasizes the need for more in-depth studies about the safety and efficacy of dengue vaccines.
PubMed: 36225478
DOI: 10.7759/cureus.28916 -
Influenza and Other Respiratory Viruses Jul 2021Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection globally. There are vaccine candidates in development, but a systematic review... (Review)
Review
BACKGROUND
Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection globally. There are vaccine candidates in development, but a systematic review on immunogenicity and safety of vaccine is lacking.
METHODS
This systematic review of RSV vaccine clinical trials was undertaken using four databases. Searches were conducted using both controlled vocabulary terms such as "Respiratory Syncytial Virus, Human," "Respiratory Syncytial Virus Infections," "Respiratory Syncytial Virus Vaccines," "Immunization," "Immunization Programs" and "Vaccines" and corresponding text word terms. The included studies were limited to clinical trials published from January 2000 to 31 December 2020. RSV infection case was defined as RSV-associated medically attended acute respiratory illness (MAARI) or RSV infection by serologically confirmed test (Western blot) during the RSV surveillance period. We calculated the relative risk of each vaccine trial with RSV infection case.
RESULTS
Of 6306 publications, 38 were included and data were extracted covering four major types of RSV vaccine candidates, these being live-attenuated/chimeric (n = 14), recombinant-vector (n = 6), subunit (n = 12) and nanoparticle vaccines (n = 6). For RSV infection cases, nine trials were involved and none of them showed a vaccine-related increased MAARI during RSV surveillance season.
CONCLUSION
LID ∆M2-2, MEDI M2-2, RSVcps2 and LID/∆M2-2 /1030s (live-attenuated) were considered the most promising vaccine candidates in infant and children. In the elderly, a nanoparticle F vaccine candidate and Ad26.RSV.preF were considered as two potential effective vaccines. A promising maternal vaccine candidate is still lacking.
Topics: Aged; Antibodies, Neutralizing; Antibodies, Viral; Child; Humans; Infant; Respiratory Syncytial Virus Infections; Respiratory Syncytial Virus Vaccines; Respiratory Syncytial Virus, Human; Vaccines, Attenuated
PubMed: 33764693
DOI: 10.1111/irv.12850 -
Vaccine Oct 2023Barriers and enablers to vaccination of care home (CH) staff should be identified in order to develop interventions to address them that increase uptake and protect... (Review)
Review
UNLABELLED
Barriers and enablers to vaccination of care home (CH) staff should be identified in order to develop interventions to address them that increase uptake and protect residents. We aimed to synthesis the evidence describing the barriers and enablers that affect the influenza vaccination uptake of care home (CH) staff.
METHOD
We searched PubMed, MEDLINE, EMBASE, CINAHL, PsycINFO, AMED, IBSS, SCOPUS to identify quantitative, qualitative or mixed-method studies. Data related to health or social care workers in CHs reported barriers or enablers were extracted and mapped to the Theoretical Domains Framework (TDF); the data within each domain were grouped and categorized into key factors affecting influenza vaccine uptake among CH staff.
RESULTS
We screened 4025 studies; 42 studies met our inclusion criteria. Thirty-four (81 %) were surveys. Five theoretical domains were frequently reported as mediators of influenza vaccine uptake: Beliefs about consequences (32 studies), Environmental context and resources (30 studies), Emotions (26 studies), Social influences (25 studies), Knowledge (22 studies). The low acceptance rate of the influenza vaccine among CH staff can be attributed to multiple factors, including insufficient understanding of the vaccine, its efficacy, or misconceptions about the vaccine (knowledge), perceiving the vaccine as ineffective and unsafe (beliefs about consequences), fear of influenza vaccine and its side effects (emotions), and experiencing limited accessibility to the vaccine (environmental context and resources).
CONCLUSION
Interventions aimed at increasing influenza vaccine uptake among CH staff should focus on addressing the barriers identified in this review. These interventions should include components such as enhancing knowledge by providing accurate information about vaccine benefits and safety, addressing negative beliefs by challenging misconceptions, managing concerns and fears through open communication, and improving accessibility to the vaccine through convenient on-site options. This review provides a foundation for the development of tailored Interventions to improve influenza vaccine uptake among CH staff.
PubMed: 37673716
DOI: 10.1016/j.vaccine.2023.08.082