Late vaccination against yellow fever of travelers visiting endemic countries

BACKGROUND: Guidelines issued by the WHO call for immunization against yellow fever (YF) at least 10 days before entering an endemic area. We assessed the extent at which travelers complied with these guidelines. METHODS: A two-phase study at one travel center in Israel. Phase I-travelers planning to visit YF-endemic areas (n = 295) were evaluated in regard to the timing of administration of YF vaccine before travel. Phase II-the specific causes of arriving late were studied prospectively in another group of 132 travelers. RESULTS: Phase I-one-half of the travelers (n = 148) headed to South America (SA), and 147 to Africa. The mean age (+/-SD) of this cohort was 30.9 (+/-14.9) years (range 6-75 years). Overall, 64 (21.7%; 95% confidence interval, 17.4-26.8) received the vaccine less then 10 days before departure. However, only 10.8% of those heading to SA arrived late, as compared to 32.7% of those heading to Africa (p < 0.0001). Phase II-a last minute's decision was the commonest reason given for arriving late (43.2%). CONCLUSION: One-fifth of travelers fail to comply with the WHO guidelines concerning YF vaccination. Travelers and travel agents alike need to be reminded of the importance of timely vaccination against YF.     

Study on the possible use of Vi polysaccharide typhoid fever vaccine to control endemic typhoid fever in Nepal

This review of literature was conducted to explore the various aspects of typhoid fever in Nepal and to identify the factors concerned in the possible use of the Vi polysaccharide typhoid fever vaccine in Nepal as the tool for prevention and control. There are hotspots of Typhoid fever in developing countries, urban areas and slums, where poor conditions of safe drinking water and sanitation prevail. The use of currently available typhoid fever vaccines, especially the Vi polysaccharide vaccine has been recommended by World Health Organization to control typhoid fever in endemic areas. However, factors like, the burden and the changing epidemiological pattern of the disease, efficacy of the vaccines, ease for intervention, cost effectiveness, financing, and programmatic issues should be considered in local settings before the introduction of vaccines as a public health tool for prevention. We concluded that the possible use of currently available Vi polysaccharide vaccine to control endemic typhoid fever in Nepal might not have the same positive impact as reported in trials from different Asian countries. The major issues to be considered are emergence of Salmonella Paratyphi A as a major cause of enteric fever, no difference in prevalence of typhoid fever in preschool and school children, similar clinical profiles and severity of typhoid and paratyphoid fever. So, an ideal vaccine that can provide the protection both to typhoid and paratyphoid fever, and the vaccination programs that also includes preschool children would be the best option for Nepal.     

Linking yellow fever vaccinator approval and renewal with training in travel medicine in New Zealand

Yellow fever is a mosquito-borne disease, which can cause serious illness. The World Health Organization (WHO) requires travellers to have vaccination against Yellow fever for all international travel going into and from Yellow fever endemic areas in order to prevent the spread of this potentially deadly disease. Only clinics and hospitals authorised by health departments of national governments can administer the disease. Yellow fever vaccination centres are often subject to inspection in many countries, although the requirements for Yellow fever vaccinators (YFV) vary from country to country. In New Zealand, approval of YFV now requires specific postgraduate training in travel medicine or its equivalent, as well as continuing professional development to maintain this status. It is expected that this will assist in improving standards of travel medicine practice in New Zealand.     

Travelling for work: seeking advice in South Africa

Sub-Saharan Africa is a common destination for occupational travellers from South Africa. Adequate preventive measures require timeous medical consultation before travel. A secondary analysis of datasets of over 8000 occupational travellers who visited travel clinics in South Africa indicated that 82% were travelling to African countries and over 50% consulted less than a week before travel. For the 70% who consult less than 10 days before departure, yellow fever certificates issued at consultation would not be valid for entry to endemic countries, although they may be protected from contracting yellow fever. The 'last minute' travel medicine consultation appears to be more common in South Africa than in Europe and North America. This may preclude South African health professionals from providing occupational travellers adequate disease prevention, particularly against vaccine-preventable infectious diseases.     

Mapping the Risk of Yellow Fever Infection

The World Health Organization coordinated a comprehensive, systematic review of the countries and areas at risk for yellow fever (YF) virus transmission. The review applied the following evidence to each country and area considered: human and non-human YF cases, human serology for anti-YF antibody obtained prior to widespread YF vaccination, altitude, vegetation, and vector distribution. The result was the categorization of countries or areas as endemic, transitional, low potential for infection, or no risk. This information was adapted to create a map that defined the areas where vaccination against YF may be recommended. Travel health professionals, countries, and public health bodies can use this information as they determine recommendations and requirements for vaccination. This paper reviews the process and outcomes of the review of YF risk, and places it in the context of providing YF vaccination.     

Impact of a Targeted Typhoid Vaccination Campaign Following Cyclone Tomas,Republic of Fiji, 2010

After a category 4 cyclone that caused extensive population displacement and damage to water and sanitation infrastructure in Fiji in March 2010, a typhoid vaccination campaign was conducted as part of the post-disaster response. During June–December 2010, 64,015 doses of typhoid Vi polysaccharide vaccine were administered to persons ≥ 2 years of age, primarily in cyclone-affected areas that were typhoid endemic. Annual typhoid fever incidence decreased during the post-campaign year (2011) relative to preceding years (2008–2009) in three subdivisions where a large proportion of the population was vaccinated (incidence rate ratios and 95% confidence intervals: 0.23, 0.13–0.41; 0.24, 0.14–0.41; 0.58, 0.40–0.86), and increased or remained unchanged in 12 subdivisions where little to no vaccination occurred. Vaccination played a role in reducing typhoid fever incidence in high-incidence areas after a disaster and should be considered in endemic settings, along with comprehensive control measures, as recommended by the World Health Organization.     

Yellow fever: an update

Yellow fever, the original viral haemorrhagic fever, was one of the most feared lethal diseases before the development of an effective vaccine. Today the disease still affects as many as 200,000 persons annually in tropical regions of Africa and South America, and poses a significant hazard to unvaccinated travellers to these areas. Yellow fever is transmitted in a cycle involving monkeys and mosquitoes, but human beings can also serve as the viraemic host for mosquito infection. Recent increases in the density and distribution of the urban mosquito vector, Aedes aegypti, as well as the rise in air travel increase the risk of introduction and spread of yellow fever to North and Central America, the Caribbean and Asia. Here I review the clinical features of the disease, its pathogenesis and pathophysiology. The disease mechanisms are poorly understood and have not been the subject of modern clinical research. Since there is no specific treatment, and management of patients with the disease is extremely problematic, the emphasis is on preventative vaccination. As a zoonosis, yellow fever cannot be eradicated, but reduction of the human disease burden is achievable through routine childhood vaccination in endemic countries, with a low cost for the benefits obtained. The biological characteristics, safety, and efficacy of live attenuated, yellow fever 17D vaccine are reviewed. New applications of yellow fever 17D virus as a vector for foreign genes hold considerable promise as a means of developing new vaccines against other viruses, and possibly against cancers.     

The revised global yellow fever risk map and recommendations for vaccination, 2010: consensus of the Informal WHO Working Group on Geographic Risk for Yellow Fever

The changing epidemiology of yellow fever and continued reports of rare but serious adverse events associated with yellow fever vaccine have drawn attention to the need to revisit criteria for the designation of areas with risk for yellow fever virus activity, and to revise the vaccine recommendations for international travel. WHO convened a working group of international experts to review factors important for the transmission of yellow fever virus and country-specific yellow fever information, to establish criteria for additions to or removal from the list of countries with risk for yellow fever virus transmission, to update yellow fever risk maps, and to revise the recommendations for vaccination for international travel. This report details the recommendations made by the working group about criteria for the designation of risk and specific changes to the classification of areas with risk for transmission of yellow fever virus.     

Reiseimpfungen

Vaccinations are a prominent part of health preparations before international travel. They can avoid or significantly reduce the risk of numerous infectious diseases. Until recently, vaccination against yellow fever was the only obligatory vaccination. However, according to updated international health regulations, other vaccinations and prophylactic measures may be required at entry from certain countries. For all routine vaccinations as recommended in Germany, necessary revaccination and catch-up of missed vaccinations should be administered before travel. At most destinations the risk of infection is higher than in Germany. Hepatitis A vaccine is generally recommended for travelers to areas of increased risk, polio vaccine for all destinations where eradication is not yet confirmed (Asia and Africa). The indications for other travel vaccines must take into consideration travel destination and itinerary, type and duration of travel, individual risk of exposure as well as the epidemiology of the disease to be prevented. Several vaccines of potential interest for travel medicine, e.g., new vaccines against malaria and dengue fever, are under development.     

Vaccination options for last-minute travellers in need of travel-related prophylaxis against hepatitis A and B and typhoid fever: a practical guide

Last-minute travellers represent a particular challenge to travel healthcare professionals, as standard vaccination schedules can take a few months to complete. This has led researchers to investigate the value of alternative accelerated schedules and existing schedules among this group, particularly with respect to time taken for an individual to seroconvert, duration of protection and multiple vaccination requirements. This paper reviews the available options for the three most common vaccine preventable diseases among travellers-hepatitis A, hepatitis B and typhoid fever. Studies suggest that even if the first dose of hepatitis A vaccine is given on the day of travel, this will provide adequate protection, and that immunity to typhoid fever can be provided in over 70% of travellers following vaccination 1 week prior to departure. For hepatitis B, an accelerated schedule of 0, 7 and 21-days has been shown to induce early protection, and is considered to be of benefit to the last-minute traveller. Practical guidelines on vaccination options from one week up to one month, as well as one month or more prior to travel are presented. This should provide guidance for travel healthcare professionals, and reassure last-minute travellers that they need not begin their journey unprotected against these three serious infectious diseases.     

Antibody responses in Japanese volunteers after immunization with yellow fever vaccine

To monitor the development of specific and cross-reactive antibody response in twenty Japanese volunteers after vaccination with live yellow fever vaccine. Serum samples were collected on various days after vaccination and examined for hemagglutination inhibition (HI) antibodies against yellow fever virus (YFV), Japanese encephalitis virus (JEV) and dengue virus (DV), neutralizing antibodies against YFV and JEV, and IgM antibodies against YFV. None of the volunteers had been previously immunized with this vaccine. Fifteen of 20 had pre-vaccinated with JEV 7 to 40 years before. Ten of the 20 had neutralizing antibodies against JEV before immunization. None of the 20 had detectable antibodies against YFV or DV before vaccination. On day 10th after the vaccination, neutralizing antibodies to YFV were detected in 6 of 19 volunteers and IgM antibodies against YFV were detected in 7 of 19. On day 14th, HI, neutralizing, and IgM antibodies against YFV were detected in all the tested sera. Neutralizing antibodies against JEV were developed in 2 volunteers and HI antibodies against JEV were increased in 3 of 6 volunteers respectively. On day 29th, cross-reactive HI antibodies for JEV and DV were detected in all the tested sera. The results indicate that YF vaccine induces YFV-specific antibodies in all the tested volunteers and that it also induces HI antibodies cross-reactive for JEV and DV. The YF vaccine has a strong immunogenicity because it is a live vaccine, and induces antibody against YFV predominantly. The international certificate of yellow fever vaccination becomes valid 10 days after vaccination. On day 14th after vaccination, we detected neutralizing antibodies against YFV from all tested volunteers, however, only 6 of 19 volunteers had detectable neutralizing antibody on the 10th day after vaccination. Therefore, the vaccine may not be perfectly effective on day 10th after the vaccination.     

Epidemiological,prevention and control updates of yellow fever outbreak in Brazil

Yellow fever is an acute viral disease endemic to tropical countries, like Brazil, where, since the 1940 s, has no significant documented outbreaks similar to that observed between 2016/2018(2 045 confirmed cases and 677 deaths; caused by the sylvatic form).The principal manipulating factors inciting this change were absence of appropriate vaccination campaigns and increased urbanization population growth in forest areas, with prevalence of the virus in the species inhabiting of these areas.The 2016/2018 outbreaks exhibited incidence in areas with historically low or no yellow fever virus activity, triggering a surge in recorded deaths-mainly in the Southeastern states of Brazil.The Brazilian government aggressively responded, reforming the countries' prophylactic measures, including vaccine implementation-as of March, 2018, switching from the former double dose regimen of the vaccine, to a single dose protocol, deemed as adequate.Moreover, some states appropriated the fractionated dosage(1/5 of the standard dose), in foresight of potential vaccine shortages.To prevent the uprising of new sylvatic yellow fever cases in Brazil, it's obligatory the development of effective combative plans, including adaptation of prophylactic measures individually(use of repellents, protective clothing etc.), applicable vaccination campaigns in every endemic region, to raise awareness to locals and visitors alike.Notwithstanding these preventative strategies, the persistence of cases and the recent outbreaks in Brazil, highlight the possible ineffectiveness of combative measures.Based on these considerations, the objective of this review was to raise more awareness of the epidemiological impact of the disease in Brazil.     

World's first malaria vaccine and its significance to malaria control in Africa

In October 2021,the World Health Organization(WHO)endorsed the first malaria vaccine,as a complementary tool for widespread use among children in at-risk areas;...     

Evolving Epidemiology of Japanese Encephalitis: Implications for Vaccination

Purpose of Review

We examine the present global burden of Japanese encephalitis (JE) in endemic populations, summarize published cases in travelers since 2009, examine current guidelines for vaccination for international travelers, and consider challenges in prevention of this vector-borne disease.

Recent Findings

We identified 11 JE cases in travelers that were published in peer-reviewed literature since 2009. JE incidence in endemic countries appears to be declining but the number of JE cases reported to the World Health Organization (WHO) varied from estimates derived from other published reports based on serosurveys or sentinel surveillance. Current JE vaccines appear to be safe and are not associated with delayed hypersensitivity in contrast to the older mouse brain vaccine.

Summary

Given differences between WHO-reported cases and local surveillance data, future research on true incidence is needed. Regular assessment will inform JE risk in travelers. National and international guidelines on JE vaccination varied; we suggest areas for improvement.

     

Antibody response after a four-site intradermal booster vaccination with cell-culture rabies vaccine.

The current World Health Organization recommendation for booster vaccination of previously immunized individuals with potential exposure to rabies is two doses of vaccine intramuscularly or intradermally on days 0 and 3. We report responses to two types of postexposure treatment of healthy individuals who had received preexposure rabies vaccination 1 year previously. Group A individuals received four intradermal doses (one-fifth of the diluent volume of vaccine per dose) on day 0, and group B individuals received two intramuscular doses on days 0 and 3. Immunogenicity of the two booster regimens was assessed by titrating the amount of neutralizing antibody (Nab). We found that the booster doses of vaccine produced remarkable responses in all subjects. Nab titers of > or = 0.5 IU/mL (acceptable antibody level for protection against rabies) were detected in all subjects on day 14, and they were shown to be consistently high 1 year after the booster vaccination. We also found that the Nab titers for group A were significantly higher (two- to eightfold) than those for group B on days 5, 14, 150, and 360 after the initial booster vaccination (P < .05). Our study shows that the four-site intradermal booster regimen with use of one-fifth of the diluent volume of cell-culture rabies vaccine on day 0 is associated with a significantly higher antibody response than is the conventional booster regimen for subsequent postexposure rabies treatment of individuals who have received preexposure rabies vaccination with cell-culture rabies vaccine 1 year previously.     

Clinical case report: Dengue hemorrhagic fever in a patient with acquired immunodeficiency syndrome

A person diagnosed with acquired immunodeficiency syndrome in 2000 and who received highly active antiretroviral therapy developed co-infection with dengue virus in 2003. In the course of the co-infection, he developed fever, thrombocytopenia (13,700 cells/mm3), petechia, and hypoalbuminemia, which are compatible with the World Health Organization criteria for a case of dengue hemorrhagic fever. Human immunodeficiency virus was not detected 30 days before co-infection and 10 days afterwards. His CD4 cell count did not show significant alterations in the two periods evaluated. He continued his course of treatment without arterial hypotension, serious hemorrhage, or other life-threatening complications.     

Skin reaction to yellow fever vaccine after immunization with rabies vaccine of chick embryo cell culture origin

Skin reaction to yellow fever vaccine was examined after immunization with rabies vaccine. The two vaccines contained substrates from chick embryo cells (rabies vaccine) and chick whole embryo (yellow fever attenuated vaccine), as well as gelatin. A prick test with gelatin showed negative results in all vaccinees examined. An intradermal skin test revealed that the yellow fever vaccine had reacted with an anti-egg protein antibody-like substance in a case with a history of egg allergy before rabies vaccination. A case inoculated two times with the rabies vaccine revealed a positive reaction to egg-white protein as well as the yellow fever vaccine. This case had no anamnesis of egg allergy. Thus, an antibody reactive to the egg-white protein and/or the yellow fever vaccine was inducible by the rabies vaccine. The reaction of this antibody was not systemic but local at the skin test by the yellow fever vaccine. The period of the rabies vaccine sensitization reactive to the yellow fever vaccine could be estimated as longer than 14.3 +/- 9.6 days (mean +/- SD), based on a follow-up examination of the positive skin reaction in 41 of 84 cases examined. We therefore conclude that the yellow fever vaccine can be safely administered at an interval of at least four weeks after a second rabies vaccination.     

Experience in global measles control, 1990-2001

Worldwide during the 1980s remarkable progress was made in controlling measles through increasing routine measles vaccination to nearly 80%. In 2000, an estimated 777,000 measles deaths occurred, of which 452,000 were in the African Region of the World Health Organization (WHO). In 2001, WHO and the United Nations Children's Fund published a 5-year strategic plan to reduce measles mortality by half by 2005. Strategies include providing a second opportunity for measles immunization to all children through nationwide supplementary immunization activities, increasing routine vaccination coverage, and improving surveillance with laboratory confirmation of suspected measles cases. In 2000, over 100 million children received a dose of measles vaccine through supplementary immunization activities, a number projected to increase during 2002-2005. Current systems for monitoring measles vaccination coverage and disease burden must be improved to accurately assess progress toward measles control goals.     

Trial of Edmonston-Zagreb measles vaccine in infants aged under nine months.

Due to the recent finding that most infants in developing countries have lost maternal antibody for measles before nine months of age, immunization of infants younger than the recommended age of nine months would help reducing the incidence of measles in these endemic areas. We conducted a trial of Edmonston-Zagreb measles vaccine which is the strain that may be more immunogenic in young infants than the widely used Schwarz strain. Forty-five infants with mean age of 25 weeks received a dose of Edmonston-Zagreb vaccine. Antibody levels were measured, using plaque neutralization test, before and about 3 months after vaccination at which mean age was 38 weeks. The seroconversion rate was 89%. Only two infants (4.4%) had immunity before vaccination. Fifteen infants (33.33%) reported some adverse reactions including fever (13.33%), rhinorrhea (8.89%), rash (4.44%) and local reactions (22.22%). All of the reactions resolved spontaneously. We conclude that Edmonston-Zagreb measles vaccine is efficacious and safe in infants aged under nine months.