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Bulletin of the World Health Organization. 2016; 94:782-784.In conclusion, WHO clinical guidelines have become increasingly evidence-based through the use of rigorous methods of synthesizing the evidence. Over the past decade, high-quality, pairwise meta-analyses have been widely used in this context, but network meta-analysis methods are increasingly important for the optimal evaluation of competing interventions. We expect that network meta-analysis will increasingly be used and adapted for developing other guidelines. (Excerpt)
World Journal of Gastroenterology. 2014 Jul 21; 20(27):8998-9016.Hepatitis B (HB) virus (HBV) infection, which causes liver cirrhosis and hepatocellular carcinoma, is endemic worldwide. Hepatitis B vaccines became commercially available in the 1980s. The World Health Organization recommended the integration of the HB vaccine into the national immunisation programs in all countries. HBV prevention strategies are classified into three groups: (1) universal vaccination alone; (2) universal vaccination with screening of pregnant women plus HB immune globulin (HBIG) at birth; and (3) selective vaccination with screening of pregnant women plus HBIG at birth. Most low-income countries have adopted universal vaccine programs without screening of pregnant women. However, HB vaccines are not widely used in low-income countries. The Global Alliance for Vaccine and Immunization was launched in 2000, and by 2012, the global coverage of a three-dose HB vaccine had increased to 79%. The next challenges are to further increase the coverage rate, close the gap between recommendations and routine practices, approach high-risk individuals, screen and treat chronically infected individuals, and prevent breakthrough infections. To eradicate HBV infections, strenuous efforts are required to overcome socioeconomic barriers to the HB vaccine; this task is expected to take several decades to complete.
Challenges and priorities in the management of HIV/HBV and HIV/HCV coinfection in resource-limited settings.
Seminars In Liver Disease. 2012 May; 32(2):147-57.Liver disease due to chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infection is now emerging as an increasing cause of morbidity and mortality in human immunodeficiency virus- (HIV-) infected persons in resource-limited settings (RLS). Existing management guidelines have generally focused on care in tertiary level facilities in developed countries. Less than half of low-income countries have guidance, and in those that do, there are important omissions or disparities in recommendations. There are multiple challenges to delivery of effective hepatitis care in RLS, but the most important remains the limited access to antiviral drugs and diagnostic tests. In 2010, the World Health Assembly adopted a resolution calling for a comprehensive approach for the prevention, control, and management of viral hepatitis. We describe activities at the World Health Organization (WHO) in three key areas: the establishment of a global hepatitis Program and interim strategy; steps toward the development of global guidance on management of coinfection for RLS; and the WHO prequalification program of HBV and HCV diagnostic assays. We highlight key research gaps and the importance of applying the lessons learned from the public health scale-up of ART to hepatitis care. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.
Changes in antiretroviral therapy guidelines: implications for public health policy and public purses.
Sexually Transmitted Infections. 2010 Oct; 86(5):388-90.INTRODUCTION: The World Health Organization (WHO) published a revision of the antiretroviral therapy (ART) guidelines and now recommends ART for all those with a CD4 cell count =350/mm(3), for people with HIV and active tuberculosis (TB) or chronic active hepatitis B irrespective of CD4 cell count and all HIV-positive pregnant women. A study was undertaken to estimate the impact of the new guidelines using four countries as examples. METHODS: The current WHO/UNAIDS country projections were accessed based on the 2007 estimates for Zambia, Kenya, Cameroon and Vietnam. New projections were created using Spectrum. CD4 progression rates to need for ART were modified and compared with the baseline projections. RESULTS: The pattern of increased need for treatment is similar across the four projections. Initiating treatment at a CD4 count <250/mm(3) will increase the need for treatment by a median of 22% immediately, initiating ART at a CD4 count <350/mm(3) increases the need for treatment by a median of 60%, and the need for treatment doubles if ART is commenced at a CD4 count <500/mm(3). Initiating ART at a CD4 cell count <250/mm(3) would increase the need for treatment by a median of around 15% in 2012; initiating treatment at a CD4 count <350/mm(3) increases the need for treatment by a median of 42% across the same projections and about 84% if CD4 <500/mm(3) was used. CONCLUSIONS: The projections indicate that initiating ART earlier in the course of the disease by increasing the threshold for the initiation of ART would increase the numbers of adults in need of treatment immediately and in the future.
Geneva, Switzerland, WHO, 2009 Nov. 25 p.Based on the latest scientific evidence, the World Health Organization (WHO) has released new recommendations on HIV treatment and prevention and infant feeding in the context of HIV. WHO now recommends earlier initiation of antiretroviral therapy for adults and adolescents, the delivery of more patient-friendly antiretroviral drugs (ARVs), and prolonged use of ARVs to reduce the risk of mother-to-child transmission of HIV. For the first time, WHO recommends that HIV-positive mothers or their infants take ARVs while breastfeeding to prevent HIV transmission.
HIV, HCV, HBV and syphilis rate of positive donations among blood donations in Mali: lower rates among volunteer blood donors.
Transfusion Clinique Et Biologique. 2009 Nov-Dec; 16(5-6):444-7.Good data on background seroprevalence of major transfusion transmitted infections is lacking in Mali. We gathered data on the rate of positive donations of human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis B virus (HBV) and syphilis among blood donations in Mali for calendar year 2007. Donations with repeatedly reactive results on screening enzyme immunoassay (EIA) were considered to be seropositive. Rate of positive donations per blood unit collected was 2.6% for HIV, 3.3% for HCV, 13.9% for hepatitis B surface antigen (HBsAg) and 0.3% for syphilis. For HIV, HBsAg and syphilis, rate of positive donations was significantly (p<0.001) higher among donations from replacement donors than those from volunteer donors, while HCV rate of positive donations was similar in the two groups. Rate of positive donations was also significantly (p<0.0001) lower in blood units from regular than from first-time donors. These data reinforce WHO recommendations for increasing the number of regular, volunteer blood donors in Africa.
Occupational transmission of bloodborne diseases to healthcare workers in developing countries: meeting the challenges.
Journal of Hospital Infection. 2009 Aug; 72(4):285-91.Healthcare workers have increased chance of acquiring bloodborne pathogens through occupational exposure in developing countries due to a combination of increased risk and fewer safety precautions. As loss of workers can seriously undermine developing health systems, it is important that risks are minimised. A literature search was conducted to investigate the risks of transmission of three pathogens: human immunodeficiency virus, hepatitis B and hepatitis C viruses; and to identify factors that influenced the risk with reference to developing countries. There are many difficulties faced by developing countries in minimising the risk of occupational exposure. Efforts have been made to address the problems both on international and national levels. It is imperative that all healthcare workers are protected in order to prevent the loss of such a crucial component of developing healthcare systems.
Contraception. 2009 Oct; 80(4):325-6.This commentary discusses women with liver diseases and the considerations that are necessary when choosing the appropriate contraceptive method due to the effect of hormones on the liver. It provides recommendations provided by the World Health Organization expert Working Group on family planning guidance to assist those women with their contraceptive options.
Seattle, Washington, Program for Appropriate Technology in Health [PATH], Bill and Melinda Gates Children’s Vaccine Program, 2001 Jan.  p. (Bill and Melinda Gates Children's Vaccine Program Occasional Paper No. 4)Hepatitis B is a killer, taking the lives of 900,000 people each year. This disease is especially dangerous for infants, since those who are infected when young may carry the infection for the rest of their lives, often without knowing it. Chronic carriers can infect others and are themselves at risk of serious liver disease later in life, including cirrhosis and liver cancer. Fortunately hepatitis B vaccine, if provided to infants, helps protect them against these problems. In effect, it is the world's first anticancer vaccine. Due to the seriousness of hepatitis B disease, and because of the high effectiveness and safety of the vaccine, the World Health Organization (WHO) recommends that it be given to all children worldwide. A recent WHO "aide-memoire" on hepatitis B is included at the end of this paper. The hepatitis B vaccine has been available for decades, but introduction into the developing world only began in the late 1980s. Currently more than 100 countries routinely provide the vaccine, but many still cannot afford to do so. The partner agencies of the Global Alliance for Vaccines and Immunization (GAVI) and the Global Fund for Children's Vaccines are working to change this situation. (excerpt)
Geneva, Switzerland, WHO, Division of Child Health and Development, 1996 Nov.  p. (Update No. 22)The question of whether breastfeeding plays a significant role in the transmission of hepatitis B has been asked for many years. It is important given the critical role of breastfeeding and the fact that about 5% of mothers worldwide are chronic hepatitis B virus (HBV) carriers. Examination of relevant studies indicates that there is no evidence that breastfeeding poses any additional risk to infants of HBV carrier mothers. The use of hepatitis B vaccine in infant immunization programmes, recommended by WHO and now implemented in 80 countries, is a further development that will eventually eliminate risk of transmission. This document discusses the issues relevant to breastfeeding and HBV transmission, and provides guidance from a WHO perspective. (excerpt)
Bulletin of the World Health Organization. 2004 Feb; 82(2):99-105.To document and characterize freezing temperatures in the Indonesian vaccine cold chain and to evaluate the feasibility of changes designed to reduce the occurrence of freezing. Data loggers were used to measure temperatures of shipments of hepatitis B vaccine from manufacturer to point of use. Baseline conditions and three intervention phases were monitored. During each of the intervention phases, vaccines were removed progressively from the standard 2–8 °C cold chain. Freezing temperatures were recorded in 75% of baseline shipments. The highest rates of freezing occurred during transport from province to district, storage in district-level ice-lined refrigerators, and storage in refrigerators in health centres. Interventions reduced freezing, without excessive heat exposure. Inadvertent freezing of freeze-sensitive vaccines is widespread in Indonesia. Simple strategies exist to reduce freezing — for example, selective transport and storage of vaccines at ambient temperatures. The use of vaccine vial monitors reduces the risk associated with heat-damaged vaccines in these scenarios. Policy changes that allow limited storage of freezesensitive vaccines at temperatures >2–8 °C would enable flexible vaccine distribution strategies that could reduce vaccine freezing, reduce costs, and increase capacity. (author's)
Journal of Chinese Sexology. 1993 Mar; (1):26-27.It is widely known that viral hepatitis is transmitted through intestinal tract infection or blood infection. However, it has not aroused much attention that the disease can be transmitted through sexual behavior. WHO has listed this disease as one of sexually transmitted diseases. Blocking the infectious link of sexual behavior is an essential tool in preventing and curing hepatitis B. This article intends to detect signs of Hepatitis B through vaginal secretion of 51 pregnant and postnatal women of childbearing age and to discuss the relationship between sexual behavior of people with Hepatitis B and clinical infection. Discussion: In China, the positive rate of surface antigen in pregnant and postnatal women is 2% to 7%, depending on the region. 1. It is 6.5% in Shenyang, lower than that in men. Pregnant and postnatal women who are surface antigen negative and who exhibit Hepatitis B symptoms people account for 22% of all surface antigen-negative people. 2. According to statistics, this study holds that 100% vaginal secretions of people with indication of Hepatitis B carry the Hepatitis B virus, and 6.6% (1/6) is strongly infectious. This indicates that chances of vaginal secretions of average women of childbearing age carrying Hepatitis B virus are high. The link between sexual behavior and the transmission of the Hepatitis B virus must be cut. (excerpt)
Challenges for communicable disease surveillance and control in southern Iraq, April-June 2003. Letter from Basrah.
JAMA. 2003 Aug 6; 290(5):654-658.The recent war in Iraq presents significant challenges for the surveillance and control of communicable diseases. In early April 2003, the World Health Organization (WHO) sent a team of public health experts to Kuwait and a base was established in the southern Iraqi governorate of Basrah on May 3. We present the lessons learned from the communicable disease surveillance and control program implemented in the Basrah governorate in Iraq (population of 1.9 million) in April and May 2003, and we report communicable disease surveillance data through June 2003. Following the war, communicable disease control programs were disrupted, access to safe water was reduced, and public health facilities were looted. Rapid health assessments were carried out in health centers and hospitals to identify priorities for action. A Health Sector Coordination Group was organized with local and international health partners, and an early warning surveillance system for communicable disease was set up. In the first week of May 2003, physicians in hospitals in Basrah suspected cholera cases and WHO formed a cholera control committee. As of June 29, 2003, Iraqi hospital laboratories have con firmed 94 cases of cholera from 7 of the 8 districts of the Basrah governorate. To prevent the transmission of major communicable diseases, restoring basic public health and water/sanitation services is currently a top priority in Iraq. Lack of security continues to be a barrier for effective public health surveillance and response in Iraq. (author's)
Journal of Viral Hepatitis. 2003 May; 10(3):157-158.Though a potent vaccine represents a powerful preventive tool, the policy of its use is governed by epidemiological and economical factors. Hepatitis A, an enterically trasmitted disease shows distinct association with socio-economic status, populations with improvement experiencing lower exposure to the virus. With the availability of vaccine, it is pertinent to consider its use in the effective control of the disease. However, with the varied epidemiological patterns and economical constraints in different countries it does not seem to be possible to evolve universal policy for immunization. Though, universal immunization may be the most effective way of control, the same is not practical for many countries. It is proposed that irrespective of endemicity of hepatitis A, high-risk groups such as travelers to endemic areas, patients suffering from chronic liver diseases, HBV and HCV carriers, tribal communities with high HBV carrier rates, food handlers, sewage workers, recipients of blood products, troops, and children from day-care centers should be immunized with hepatitis A vaccine. In addition, for populations with intermediate prevalence, infants, children from affordable families may be immunized. As coupling the vaccine with EPI schedule would be beneficial, use of combined A & B or A, B & E vaccine may be an attractive alternative. (author's)
Journal of Viral Hepatitis. 2003 Mar; 10(2):141-149.Hepatitis B (HB) is thought to be an expanding health problem in Russia. The incidence of infection was estimated from mandatorily reported HB cases in St Petersburg. The two-sided t-test for independent samples and the LOESS (locally-weighted regression) smoother were used to compare the age at infection for symptomatic, asymptomatic and chronic infections, by gender. The force of infection was estimated from seroprevalence data (907 sera taken in 1999) using a newly developed nonparametric method based on local polynomials, as well as an earlier method based on isotonic regression and kernel smoothers. With the local polynomial method, pointwise confidence intervals (95%) were constructed by bootstrapping. On average, men contracted HB infection at a significantly younger age than women (in 1999, 21.8 vs 22.7 years, respectively). The overall male to female ratio was 1.92. In 1999 the overall incidence almost doubled compared with the preceding years and tripled among the age groups with highest incidence (15–29-year olds: 85% of cases in 1999). The incidence increase was associated with a lower average age at infection (24.1 years in 1994 vs 22.1 years in 1999). The age and gender-specific force of infection estimates generally confirmed the incidence estimates and emphasized the usefulness of local polynomials to do this. Hence HB transmission in St Petersburg occurs mainly in young adults. The dramatic increase of infections in 1999 was probably due to injecting drug use. Without intervention, HB virus is expected to continue to spread rapidly with a greater proportion of female infections caused by sexual transmission. These trends may also provide an indication for HIV transmission. (author's)
Immunization of children at risk of infection with human immunodeficiency virus. [Immunisation des enfants courant le risque d'infection par le virus d'immunodéficience humain]
Bulletin of the World Health Organization. 2003; 81(1):61-70.This paper reviews the English language literature on the safety, immunogenicity and effectiveness in children infected with the human immunodeficiency virus (HIV) of vaccines currently recommended by WHO for use in national immunization programmes. Immunization is generally safe and beneficial for children infected with HIV, although HIV-induced immune suppression reduces the benefit compared with that obtained in HIV-uninfected children. However, serious complications can occur following immunization of severely immunocompromised children with bacillus Calmette–Guérin (BCG) vaccine. The risk of serious complications attributable to yellow fever vaccine in HIV-infected persons has not been determined. WHO guidelines for immunizing children with HIV infection and infants born to HIV-infected women differ only slightly from the general guidelines. BCG and yellow fever vaccines should be withheld from symptomatic HIV-infected children. Only one serious complication (fatal pneumonia) has been attributed to measles vaccine administered to a severely immunocompromised adult. Although two HIV-infected infants have developed vaccine-associated paralytic poliomyelitis, several million infected children have been vaccinated and the evidence does not suggest that there is an increased risk. The benefits of measles and poliovirus vaccines far outweigh the potential risks in HIV-infected children. The policy of administering routine vaccines to all children, regardless of possible HIV exposure, has been very effective in obtaining high immunization coverage and control of preventable diseases. Any changes in this policy would have to be carefully examined for a potential negative impact on disease control programmes in many countries. (author's)
Geneva, Switzerland, WHO, Division of Family Health, Programme of Maternal and Child Health and Family Planning, 1991 Dec. , 122 p. (WHO/MCH/91.10)This WHO consultation on maternal and perinatal infections reviews the epidemiology of these infections, examines the effectiveness of known intervention strategies to prevent and treat these infections, notes gaps in current knowledge, and develops recommendations for implementation of appropriate control strategies. The report is geared toward maternal and child health professionals in developing countries where maternal and perinatal infections cause considerable morbidity and death. These countries have limited resources for health care (e.g., US $5-10/person), largely due to the worsening economic situation. The report centers on the feasibility, effectiveness, and cost of interventions to prevent, treat, and control the infections. It has summary cost-effective analyses of maternal and perinatal infections and proposed interventions using 3 different hypothetical country situations to help policymakers decide on priorities and policies on prevention, treatment, and control of these infections. The report dedicates a chapter to each infection (syphilis, neonatal tetanus, malaria, hepatitis, HIV infections, chlamydial infections, herpes simplex infection, Group B Streptococcal infections, and maternal genital infection causing premature birth and low birth weight). Each chapter addresses their clinical and public health significance; prevalence in pregnant women and transmission from mother to fetus/infant; clinical effects; prevention, treatment, and control; and cost effectiveness and feasibility of various interventions. Based on public health importance, feasibility, and affordability, the consultants agreed that national and international programs should place the highest priority on these perinatal infections: gonococcal ophthalmia neonatorum, maternal and congenital syphilis, neonatal tetanus, hepatitis B, and maternal puerperal infections.
Strengthening immunization systems and introduction of hepatitis B vaccine in Central and Eastern Europe and the Newly Independent States.
Vaccine. 2002; 20:1475-9.On June 24-27, 2001, the Viral Hepatitis Prevention Board conducted a meeting in St. Petersburg, Russia. The aim of this meeting was to review and strengthen a 1996 immunization initiative and to introduce the hepatitis B vaccine in central and eastern Europe and in the Newly Independent States. This meeting was organized in collaboration with Centers for Disease Control and Prevention, the Global Alliance for Vaccines and Immunization (GAVI), the Children's Vaccine Program, WHO and the UN International Children's Emergency Fund (UNICEF). This conference has several partner agencies that augment the process of enforcing affordable and sustainable programs. This partnership has helped encourage 11 countries to apply for support for immunization services and universal hepatitis B immunization from GAVI/The Vaccine Fund. Information on how to improve hepatitis B programs was also elicited.
BULLETIN OF THE WORLD HEALTH ORGANIZATION. 1998; 76(1):99-100.More than half of the injections administered in many developing countries are unsterile, resulting in millions of cases of viral hepatitis B and C and increased transmission of HIV infection. Since both hepatitis B and C and HIV viruses have a long incubation period and take a long time to kill, the association with an injection is seldom made. To combat this problem, the World Health Organization (WHO) has distributed millions of sterilizable needles and syringes and steam sterilizers around the world. WHO's Expanded Program on Immunization (EPI) has stimulated the development of the one-time "autodestruct" syringe and seeks to make this the standard injection device in all countries. The EPI has called upon all donors, international agencies, and health departments to bundle a supply of autodestruct syringes and boxes for their disposal after use with all vaccines supplied for emergency purposes. Education to change attitudes of the public and health providers remains a vital component of the campaign to reduce the risk of inappropriate and unsterile injections.
INDIAN PEDIATRICS. 1997 Jun; 34(6):518-20.Globally, there are over 350 million carriers of hepatitis B virus (HBV). In areas where persistent HBV infection is endemic, transmission is generally either perinatal or horizontal (through close contact between children). Given the finding of small amounts of hepatitis B surface antigen in breast milk, breast feeding has been suggested as an additional mechanism of HBV transmission. The research literature includes no documentation that breast feeding confers any additional risk to infants of HBV carriers, however. Active immunization with hepatitis B vaccine can prevent development of the persistent carrier state in 70-90% of infants of carrier mothers. Administration of hepatitis B immune globulin within 24 hours of birth together with the first dose of vaccine increases this rate to 85-90%. The World Health Organization has recommended that all infants receive hepatitis B vaccine as a part of routine childhood immunization. Where feasible, the first dose should be administered within 48 hours of birth. Even in settings where HBV is highly endemic and immunization is not available, exclusive breast feeding for 4-6 months remains the recommended method of infant nutrition.
VOX SANGUINIS. 1994; 67(4):377-81.As part of an effort to monitor the safety of global blood transfusion services, the World Health Organization circulates a questionnaire for use in a database on blood safety. In 1992, 67% of countries responding to the survey (100% of developed, 66% of developing, and 46% of less developed countries) were screening all blood donations for HIV antibodies and 87% of these countries (100% of developed, 92% of developing, and 63% of less developed countries) carried out supplementary testing to confirm positive results. All developed countries, 72% of developing, and 35% of less developed countries screen blood for hepatitis B surface antigen and 94%, 71%, and 48%, respectively, screen for syphilis. The primary reasons for inadequate blood testing are the cost of test kits and reagents and the unreliability of supplies. The proportion of safe donors is highest in systems where all donors are voluntary and nonremunerated--conditions that exist in 85% of developed countries but only 15% of developing and 7% of less developed countries. Blood safety would also be improved by more appropriate use of transfusions and the provision of alternatives such as saline and colloids. Other problems include insufficient blood supply (e.g., none of the less developed and only 9% of developing countries collect 30 units or more per 1000 population per year) and inadequate quality assurance in all aspects of preparatory testing.
VACCINE AND IMMUNIZATION NEWS. 1996 Oct; (2):4-5.There are an estimated 350 million chronic carriers of hepatitis B virus (HBV) worldwide, most of whom are children, and an estimated 1.2 million people die annually from an HBV-related disease. However, immunizing infants against HBV could prevent new infections and reduce levels of HBV-related morbidity and mortality worldwide. To that end, the Expanded Program on Immunization in 1991 set 1997 as the target date for all countries' national immunization programs to have adopted HBV vaccine into their universal immunization package. 80 World Health Organization (WHO) member states have met this goal and 10 more countries plan to soon incorporate HBV. That means that there are still 110 WHO member states not using vaccine against HBV. The vaccine is now reaching only 20% of the world's infants. Real problems remain to be surmounted in delivering HBV vaccine to children in the poorest countries, places which cannot afford the vaccine but often have a heavy burden of hepatitis B disease. 63 priority countries have been identified, countries in which more than 5% of the population is chronically infected and there is an efficient immunization infrastructure.
Implementing the ICPD Plan of Action in Central Asian Republics and Kazakhstan (CARAK). Kyrgyzstan. Breast-feeding is best.
ENTRE NOUS. 1995 May; (28-29):11.The socioeconomic problems which began in Kyrgyzstan in 1990 have impacted on the health of the people living there. A major decline in income, living standards, and social security is reflected in the low fertility rate, high maternal and infant mortality, and shorter life expectancy. Tuberculosis, viral hepatitis, anemia, hypertrophy, and rachitis have become very common in young children. In order to remedy this situation, breast feeding has gained the importance of a national program. Other unresolved issues include the high neonatal mortality rate, and the increasing maternal mortality rate (from 76.4 per 100,000 live births in 1991 to 84.2 per 100,000 currently). There has been a functioning family planning service and a system of social patronage since 1989. In the latter system, a social worker takes charge of families at risk. One worker on average attends 30 families. The International Planned Parenthood Federation has financed 689 social patronage workers over the past year. International organizations have supported the supply of contraceptives through humanitarian aid. Because of this, the number of women accepting family planning is rising and the fertility rate is decreasing (from 28.2 per 1000 in 1991 to 26.9 in 1993).
ANALES ESPANOLES DE PEDIATRIA. 1992 Jun; 36 Suppl 48:189.New vaccine developments will reflect achievements of the World Health Organization's (WHO) Expanded Programme on Immunization (EPI), as well as resistance from the public toward increasing numbers of vaccines. WHO's EPI program has concentrated on tuberculosis, diphtheria, tetanus, whooping cough, polio, and measles. 35 countries are attempting to control hepatitis B with universal vaccination. Now some countries are also recommending vaccination against Haemophilus influenza, mumps, and rubella. The complexity of multiple injections has prompted new research on acellular vaccines for pertussis, hepatitis A and B, varicella, and malaria. Combined vaccines and new adjuvants are also targets of intense research. Vaccines are a priority, because they are among the most cost-effective of medical interventions.