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Información esencial sobre las vacunas y la inmunización

Why is Vaccination important?

    As highlighted by the WHO, vaccination is one of the most cost-effective health interventions available, saving millions of people from illness, disability and death each year. Effective and safe vaccines, which protect against more than 20 serious diseases, via what is called immunization are available and many promising new vaccines are being developed. Vaccinations can provide protection not just for the vaccinated person, but for the population as a whole as well. This phenomenon, called community immunity or herd immunity, occurs when a large portion of the population is vaccinated, usually over 85%, depending on the disease.

    For WHO, the seven key reasons to immunize are that ;

    1. Immunization saves lives: more than 3 million lives worldwide each year, and it saves millions more from suffering illness and lifelong disability
    2. it is a basic right and a strategic, relatively inexpensive component of poverty reduction programmes:
    3. Vaccine-preventable diseases still pose a risk;
    4. Diseases can be controlled and eliminated;
    5. Immunization is cost-effective;
    6. Children depend on health systems to provide safe, effective and inexpensive immunization;
    7. Every child needs to be vaccinated

    WHO has estimated that if all the vaccines now available against childhood diseases were widely adopted, and if countries could raise vaccine coverage to a global average of 90%, by 2015 an additional two million deaths a year could be prevented among children under five years old.

    How does a vaccine work?

      Some white blood cells produce antibodies , molecules that bind to specific parts of the invading germs called antigens, targeting them for attack and destruction by white blood cells. The first time the body encounters a germ, it takes several days to make and use all the germ-fighting tools needed to get over the infection, including the production of antibodies.

      After the first infection, the immune system keeps a memory for years, decades, or even a lifetime of the germs for which it had already produced antibodies, forming the body’s immunity. When the body encounters the same germ, the defense response is both faster and stronger.

      Vaccines typically contain an antigen so that the immune system can build a memory of it. These can be on the form of attenuated or inactivated viruses or of a portion of the surface of a bacterium or virus that the immune system recognizes as foreign. A vaccine may also provide a non-active version of a toxin – a poison produced by a bacterium – so that the body can devise a defense against it. (WHO)

      Vaccines contribute thus to develop immunity by imitating an infection without causing the illness, and by causing the body to produce the antibodies and the memory of the infection.

      What are the most recommended vaccinations?

        Vaccines have the potential for eradicating, eliminating or controlling a number of serious, life-threatening or debilitating infectious diseases. Smallpox is the first disease that was eradicated through the use of vaccines in 1979, and currently poliomyelitis is close to eradication. Over the past decade, immunization programmes have added new and underused vaccines to the original six – diphtheria, tetanus, pertussis, measles, polio, and tuberculosis – given to young children. They include vaccines against hepatitis B, Haemophilus influenzae type b (Hib) (producing meningitis), mumps, pneumococcal disease, rotavirus, rubella, and – in countries where needed – yellow fever and Japanese encephalitis.

        Main diseases that can be prevented by vaccines (WHO)

        Anthrax Hepatitis A, B and E Polyomyelitis Human papilloma-virus (HPV)
        Measles Diphteria Typhoid fever Varicella and herpes zoster (shingles)
        Rubella Mumps Pneumococcal disease Rotavirus gastroenteritis
        Cholera Tetanus Tick-borne encephalitis Yellow fever
        Meningococcal Disease Pertussis (Whooping cough) Haemophilus influenza type b Japanese encephalitis
        Influenza Tuberculosis Rabies  

        Among more recent vaccines, bringing the total number to over 30, significant progress has been achieved in the introduction of Human papilloma-virus (HPV), pneumococcal and rotavirus vaccines in the European Region. Twenty-six countries have recommended or funded use of HPV vaccine (which is the only vaccine that can prevent cancer of the cervix) for national immunization programmes. In all countries the primary target group is girls before they are sexually active, in the age range of 9-12 years. Most recommendations also advise vaccinating populations of older adolescent girls and young women.

        Thirty-one countries have also recommended universal vaccination with pneumococcal conjugate vaccines in children. Rotavirus vaccines are included in the routine immunization schedule in 12 countries, including three middle-income countries.

        Are there risks associated to vaccination?

          As once-common diseases become less frequent, fear of the diseases themselves tend to become overshadowed by vaccine safety concerns, sometimes fueled by misinformation about vaccination, says the WHO.

          In the US, the Centers for Disease Control and Prevention (CDC) established the Vaccine Adverse Events Reporting System (VAERS), Approximately 30,000 VAERS reports are filed annually, with 10-15% classified as serious (resulting in permanent disability, hospitalization, life-threatening illnesses or death). However, according to CDC, most side effects of vaccines are minor and temporary, and the relative rate of serious side effects or of deaths is extremely low. One thing to keep in mind is that the risk from getting a disease like diphtheria or tetanus is much greater (1 out of 5 cases of tetanus is fatal, for instance) than any risk of side effect from vaccines. Most studies have demonstrated that, for example, the apparent link between vaccination of babies and sudden infant death syndrome (SIDS), is purely coincidental. www.cdc.gov/vaccinesafety/activities/vaers.html 

          CDC highlighted some misconceptions about vaccination :

          • "Diseases were already disappearing before vaccines, because of better hygiene and sanitation". This misconception is often cited as an argument against vaccination. Survival rates had been getting better before the introduction of vaccines, but dramatic decreases in number of cases were seen only after the introduction of vaccines.
          • "The majority of people who get diseases have been vaccinated". In fact, no vaccine is 100% effective, and indeed some vaccinated people will not develop immunity (vaccine effectiveness is usually 85 to 95%). When there is an outbreak of a disease, the people who are affected will be those who have not been vaccinated, and those who were, but did not develop immunity. In populations where the vast majority of people have been vaccinated, there are people who are vaccinated but not immune than people who are not vaccinated.
          • "The diseases that are preventable with vaccines have been virtually eliminated, and so there is no need for children to be vaccinated anymore". Vaccination protects not only the person who is getting vaccinated, but also the people around him, more specifically those people who are the most vulnerable. If vaccination stops, then any outbreak could become devastating.
          • "Multiple vaccinations at an early age is taxing for a young child’s immune system and can be harmful." Children are exposed to germs everyday, and the immune system handles them without getting overloaded. Available scientific data show that there is not harm for the immune system of young children.

          Is there new progress in vaccination?

            According to a UNICEF-WHO-WB report (2009) the first decade of the 21stcentury has been the most productive in the history of vaccine development. New life-saving vaccines have been developed, thanks to the “maturing” of breakthroughs in biotechnology that occurred in the 1980s and 1990s, and others will soon be available. New vaccines are indeed urgently needed to reduce illness and deaths from high-burden diseases such as malaria, tuberculosis, and AIDS. A large number of – over 80 candidate vaccines according to recent unpublished data are in the late stages of research and development and about 30 of these candidates aim to protect against diseases for which there are no vaccines currently available.

            In the meantime, most low-cost traditional vaccines are now produced by vaccine manufacturers in developing countries, and public-private partnerships are accelerating the availability of new vaccines with systems in place that ensure the safety, effectiveness, and quality of all vaccines.

            New vaccine delivery systems are also anticipated. Devices that use needles may have been largely replaced with new approaches such as aerosol formulations sprayed in the nose (already available for an influenza vaccine), or lungs (currently being tested for several vaccines), adhesive skin patches, drops under the tongue, and oral pills.

            What is the situation of vaccination in Europe?

              In Europe, immunization levels are very high. Vaccination policies are planned and implemented at the country level, and not at the level of the WHO European Region. All 53 Member States have agreed to the priority goals of eliminating measles and rubella and maintaining polio-free status. The European Region faced serious threats to the achievement of these goals in 2013, with outbreaks of measles in many countries. Most cases were in the general population, but some specific groups were particularly affected, like in the case of an outbreak in the Netherlands that affected unvaccinated orthodox Protestants. In the WHO European region, despite a large outbreak of rubella in Poland and environmental detection of wild poliovirus in Israel, poliomyelitis is not present, and both measles and rubella are on the verge of being eliminated if vaccination coverage can be assured, and the WHO European Region established 2015 as the target date for elimination of measles and rubella.

              Information to the greater public is an important part of the strategy of the European WHO regional office to help raise awareness and respond to concerns about vaccine safety.

              What is the vaccination status in South America?

                In South America, the Global Vaccine Action Plan (GVAP), which was launched in 2005 is an effort to strengthen the achievements of immunization and continue urging governments to persist with their commitment to protect their populations from vaccine-preventable diseases. The GVAP builds on the Global Immunization Vision and Strategy (GIVS), which was launched in 2005 and was the first 10-year strategic framework to maximize the potential of immunization. The GVAP reiterates the existing global goals and proposes new goals for this Decade of Vaccines (2010-2020).

                In the Americas, the GVAP will complement the Regional Immunization Vision and Strategy, a document that was developed to adapt the GIVS to regional priorities in 2007. The monitoring and reporting mechanisms for measuring the Region’s progress regarding the GIVS will be used to monitor the implementation of the GVAP.

                Among the objectives of the Technical Advisory Group (TAG) on Vaccine‐preventable Diseases of the Pan American Health Organization (PAHO) are: to interrupt wild poliovirus transmission globally, to reach, by 2015, 90% national coverage and 80% in every district or equivalent administrative unit with vaccines containing diphtheria-tetanus pertussis, and to reduce by two thirds, between 1990 and 2015, the under-five mortality rate.

                In 2012, the International Expert Committee (IEC) presented progress made in the documentation and verification process to the WHO Member States. In its regional report, it concluded that: “it appears that the interruption of endemic measles and rubella virus transmission has been achieved.” However, the report establishes that: “as part of the documentation and verification process, several Member States have identified challenges they need to overcome for maintaining elimination of measles, rubella and CRS. In addition, some countries have reported weakness and failures in their national surveillance systems and routine immunization programs, which must be dealt with.”

                The Region of the Americas has always been a pioneer and a global leader in immunization. These achievements are now potentially at risk, due to the increased complexity of the decision-making and planning that must be undertaken by the national immunization programs (NIPs). New vaccine adoption without an adequate evidence base and careful planning could lead to an overall decrease in performance of the NIPs. The Programmes could start facing problems of underfunding and inefficiencies, resulting in decreased public health benefits.

                Among new vaccines needs, dengue occurrence remains at historic highs. In 2012, above one million dengue cases were reported in 43 countries and territories of the Americas, and two dozen vaccine candidates are currently in preclinical development and five in clinical development. While only one candidate for Plasmodium vivax malaria vaccine is in clinical development, several P. falciparum vaccines are tested in clinical trials.

                Yellow fever continues to be a significant public health problem for the 13 countries of the Americas with endemic areas. One yellow fever vaccine dose is sufficient to provide sustained immunity and life-long protection against the disease, The vaccination strategies include:

                1. introduction of the yellow fever vaccine in national immunization programs for children 1 year of age in every country with endemic areas;
                2. vaccination campaigns during inter-epidemic periods;
                3. vaccination campaigns in response to outbreaks or epizootics (epidemics in animals), and
                4. administration of the vaccine to those traveling to areas where there is a risk of transmission of the yellow fever virus, except for those for whom vaccination is contraindicated.

                What the vaccination status in the United States ?

                  In United States, vaccination coverage levels among adults are low. Improvement in adult vaccination is needed to reduce the health consequences of vaccine-preventable diseases among adults and to prevent pertussis morbidity and mortality in infants, who need the protection afforded by the Tdap vaccination during pregnancy recommendation. In 2012, adult vaccination coverage in the United States for diseases other than influenza was similar to 2011, except for modest increases in Tdap vaccination for adults aged 19–64 years, herpes zoster vaccination among older adults, and HPV vaccination among women aged 19–26 years, with no improvements in coverage for the other vaccines recommended for adults. Many adults have not received one or more recommended vaccines.

                  What is the global world’s state of vaccination coverage?

                    In 2012, (last data available) Immunization currently prevents an estimated two to three million deaths every year in all age groups from diphtheria, tetanus, pertussis (whooping cough), and measles. In 2012, an estimated 83% (111 million) of infants worldwide were vaccinated with three doses of Diphtheria-Tetanus-Pertussis (DTP3) vaccine.

                    Three WHO regions ― the Americas, Europe and Western Pacific ― maintained over 90% DTP3 immunization coverage, the Western Pacific reaching 97%. The total number of children who died from diseases preventable by vaccines currently recommended by WHO, is estimated to about 1.5 million.


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