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Clinical evidence brief Immunisation 3. National immunisation program Immunisation is the process of obtaining ‘immune status’ through vaccination. To ensure immunisation rates remain at a high level, Australia has a comprehensive National Immunisation Program (NIP). The NIP Schedule includes 16 vaccines for mass childhood immunisation programs and influenza and Hepatitis A for at-risk adults. 1. Public health benefits The public health benefits of immunisation include: • reduction in illness, disability and death • control, prevention and eradication of disease • protection of both the individual and the community from vaccine preventable diseases (VPD) • a cost effective health strategy. 2. Herd immunity Herd immunity is the effect achieved when a significant portion of a population is vaccinated providing a measure of protection for individuals who do not have immunity. Only a small fraction of the population can be left unvaccinated for this method to be effective. Unvaccinated individuals may include those who cannot safely receive vaccines for various reasons such as impaired immunity, failure to respond adequately to vaccination, or egg allergies.1,2 The control of highly infectious diseases, such as measles, requires 95% of the population to be vaccinated to prevent the transmission of the disease. Diphtheria, a less infectious disease, requires a lower percentage of the population to be vaccinated and as a result there have been no cases of diphtheria in Australia since the 1970s. The pneumococcal vaccine which was introduced to protect children against diseases caused by the bacterium, Streptococcus pneumoniae, has also been shown to provide protection for susceptible unvaccinated elderly people due to a reduction in circulation of the bacterium in the community.3 3. Vaccines4,5 Vaccines contain active components such as attenuated live viruses, inactivated viruses, modified or partial forms of the virus or bacteria or the toxin produced by the bacteria. The antigen in the vaccine is altered from its original form so it no longer causes disease but produces an immune response. Active components used in a vaccine are: • Live viruses used in vaccines are weakened (or attenuated) limiting the virus’ ability to replicate and are able to induce an immune response without causing severe disease. The advantage of live, attenuated vaccines is that only one or two doses usually provide whole of life immunity. However, these vaccines cannot be given to people with severely impaired immunity, as a greatly weakened immune system may not be able to limit reproduction of the vaccine virus. Women receiving live viral vaccines must be advised against falling pregnant within 28 days of vaccination. • Inactivated viruses are inactivated by formaldehyde so the pathogenic effects are rendered inactive but the antigenicity is preserved. The virus is incapable of replication after vaccination but it is still recognised by the body’s immune system. These vaccines can be given to people with impaired immunity. Several doses may need to be given to achieve long-term immunity, and persons with impaired immunity may not respond to even multiple doses. • Part of the virus or bacteria is used in certain vaccines to induce immunity e.g. hepatitis B vaccine is composed of a protein from the surface of the virus, haemophilus influenzae type b (Hib) vaccine 2013 only the outer coating or polysaccharide is used and joined to a protein so that the immune system responds to it. These vaccines can be administered to people with weakened immunity, although, if the person’s immune system is too weak, they may not develop a satisfactory immune response. • Toxins produced by the bacteria are chemically inactivated to produce a vaccine that is known as a toxoid. E.g. diphtheria and tetanus-containing vaccines. Tetanus vaccination stimulates the production of antitoxin, which protects against the toxin produced by the organism. Having tetanus infection does not induce a long‑term immune response and nonimmune individuals who contract tetanus must be fully vaccinated to protect against future exposure. References 1 National Prescribing Service. Why be vaccinated. At: www. nps.org.au/medicines/immune-system/vaccines-andimmunisation/for-individuals/why-be-vaccinated 2 Understanding childhood immunisation booklet (revised June 2010). Immunise Australia Program. At: www.immunise.health. gov.au/internet/immunise/publishing.nsf/Content/IMM52-cnt 3 The Science of immunisation. Australian Academy of Science November 2012. At: www.science.org.au/policy/documents/ AAS_Immunisation_FINAL_LR_v3.pdf 4 The Australian Immunisation Handbook 9th Edition. At: www. health.gov.au/internet/immunise/publishing.nsf/Content/ Handbook-home 5 Vaccine and its Components Fact Sheet. National Council for Immunisation Research and Surveillance. At: www.ncirs.edu.au/ immunisation/fact-sheets/vaccine-components-fact-sheet.pdf Practice points These practice points are taken from the Immunisation inPHARMation, Facts Behind the Fact Card article. Discussing childhood immunisation with parents4,12 It has been estimated that immunisation currently saves three million lives per year throughout the world while remaining one of the most cost effective health interventions. When immunisation rates in the community are very high the number of cases of certain diseases can be reduced. For example, Haemophilus influenzae type b (Hib) vaccine was introduced into the Australian NIP schedule for all children in 1993. In 1992, there were 560 cases of Hib disease notified but in 2006, only 22 cases were notified. Despite a very good record of effectiveness and safety, there are still people who have reservations about immunisation. To make informed decisions, parents need to understand the benefits and risks of vaccination, or not vaccinating, their children. Parents do not usually understand how immunisation protects the child, and the diseases are often not seen as serious. When discussing concerns about immunisation with parents or adults, it is important to recognise that a logical demonstration of the weaknesses in arguments against immunisation needs to be combined with listening and other good communication skills. Two useful resources to assist pharmacists in discussing immunisation issues with parents are Immunisation Myths & Realities, A Guide for Providers and Understanding childhood immunisation, accessible at www.immunise. health.gov.au Onset, extent and duration of immunity2 Immunity does not occur immediately after vaccination. Activation of the normal immune response takes approximately two weeks. Many vaccines require several booster doses to be given for full immune response to occur and, even when all the doses of a vaccine have been given, not everyone will be immune. Measles, mumps, rubella, tetanus, polio, hepatitis B and Hib vaccines protect more than 95% of children who have completed the recommended immunisation course. Three doses of whooping cough vaccine will protect about 85% of children immunised, and will reduce the severity of the disease in the other 15% of children if they do catch whooping cough. One dose of meningococcal C vaccine at 12 months of age will protect more than 90% of children immunised.1,8 The protective effect of immunisation is not always lifelong. Some vaccines, such as tetanus, can last up to 30 years, then a booster dose may be required. (Note: A booster dose may be required earlier (e.g. after 10 years) in the presence of a tetanus prone wound.) Other vaccines, such as whooping cough, give protection for about five years after a full course.1,8 A two‑dose course of hepatitis A vaccine given 6–12 months apart is thought to give protection for about 20 years.1,2 Contraindications to vaccines 2,8 There are only two absolute contraindications applicable to all vaccines: • a known anaphylactic sensitivity to any component of the relevant vaccine • anaphylaxis following a previous dose of the relevant vaccine. Further contraindications to live attenuated vaccines are: • immunosuppressed people regardless of whether the suppression is caused by disease or treatment • adults treated with systemic corticosteroids in excess of 60 mg of prednisolone (or equivalent) per day (vaccination should be postponed until at least three months after treatment has stopped) • pregnancy. For further explanation, see the Australian Immunisation Handbook 9th edition. If a child has an acute febrile illness (current temperature ≥ 38.5°C) the vaccination should be postponed for 2–3 days until the child is well. The following are NOT contraindications to any of the vaccines in the NIP Schedule: • family history of any adverse events following immunisation • family history of convulsions • previous pertussis-like illness, measles, rubella, mumps or meningococcal infection • prematurity (vaccination should not be postponed) • neurological conditions including cerebral palsy and Down’s syndrome • contact with an infectious disease • asthma, eczema, atopy, hayfever or ‘snuffles’ • treatment with antibiotics • treatment with locally acting (inhaled or low-dose topical) steroids • child’s mother is pregnant • child to be vaccinated is being breastfed • woman to be vaccinated is breastfeeding • history of neonatal jaundice • low weight in an otherwise healthy child • recent or imminent surgery. Late adverse effects of vaccines2 Long term surveillance of vaccines is conducted to ensure unanticipated adverse effects are detected. Through the systematic collection of data and analysis of reports, some vaccines have been shown to cause serious late events, although the rate is always hundreds to thousands times less frequent than the disease complication. For example: • Approximately one in 1,000,000 doses of MMR vaccine among children causes acute encephalitis occurring 8–9 days after vaccination. In comparison, one in 500 cases of naturally-acquired measles results in severe acute encephalitis.5 • Vaccines containing diphtheria and tetanus have been implicated in causing brachial neuritis with an incidence of approximately one in 100,000 (adults). • One additional case of Guillain-Barre syndrome has been detected in every one million people vaccinated against influenza.5 Although late adverse effects have been reported following immunisation, there is strong epidemiological evidence that there is no causal association between: • sudden infant death syndrome (SIDS) and any vaccine • autism and MMR vaccine • multiple sclerosis and hepatitis B vaccine • inflammatory bowel disease (IBD) and MMR vaccine • diabetes and Hib vaccine • asthma and any vaccine. Practice points Seasonal influenza vaccines normally contain three strains of virus; two current influenza A subtypes, H1N1 and H3N2, and influenza B, representing recently circulating viruses. The H1N1 influenza A strain (known as swine ‘flu) is incorporated in the 2013 seasonal influenza vaccines. However, the current influenza vaccines will not give protection against the H5N1 (avian) virus. Although seasonal influenza vaccines contain minimal amounts of egg protein, they can be used in certain egg-sensitive individuals. Referral to a specialist immunologist is recommended in such cases, however.5,6 It is important that people in at-risk groups continue to have annual influenza vaccines. If a child under the age of nine years is receiving the vaccine for the first time, they will require two doses at least one month apart.2 Vaccination is best given in autumn; however, it can be given as early as February. Influenza vaccine can be administered concurrently with other vaccines, including pneumococcal polysaccharide vaccine and all the scheduled childhood vaccines. Annual influenza vaccination is recommended for the following groups:13 • all people aged 65 years and older • Aboriginal and Torres Strait Islander people over 15 years of age • children (≥ six months of age) and adults with chronic illnesses including: • heart conditions • lung/respiratory conditions including asthma • diabetes (and other chronic metabolic diseases) • kidney disease • impaired immunity • chronic neurological conditions including multiple sclerosis and seizure disorders • haemoglobinopathies (a range of genetically inherited disorders of red blood cell haemoglobin) • pregnant women • residents of nursing homes and other long-term care facilities. In addition, it is important that people who care for, or who are in close contact with, people who are at particular risk, also avoid spreading the infection. Annual influenza vaccination is also strongly recommended for travellers and people providing essential community services. The National Health and Medical Research Council (NHMRC) also recommends that influenza vaccination can be given to any person aged 6 months or more who wishes to reduce the chance of becoming ill with influenza. Influenza vaccination should be delayed when a person has a high fever or a moderately severe illness, but can generally be given once the illness is resolved. Avian flu14 There are many different subtypes of type A influenza viruses. Influenza A viruses are constantly changing, and it is possible for viruses that infect birds to adapt over time to infect and spread among humans. Influenza A (H5N1) virus is a highly pathogenic influenza A virus subtype that occurs mainly in birds. It does not usually infect people, but about 160 human cases have been reported by the World Health Organization since January 2004. Most of these cases have occurred as a result of people having direct or close contact with infected poultry or contaminated surfaces. So far, the spread of H5N1 virus from person‑to‑person has been rare and has not continued beyond one person. There is currently no commercially available vaccine to protect humans against the H5N1 virus that is emerging in Asia and Europe. However, vaccines are being developed. Studies to test a vaccine to protect humans against H5N1 virus began in April 2005, and a series of clinical trials is in progress. As a pandemic vaccine needs to be a close match to the actual pandemic virus, commercial production cannot begin prior to emergence and characterisation of the pandemic virus. On current trends, it appears likely that most developing countries will have no access to a vaccine during the first wave of a pandemic and perhaps throughout its duration. PSA4007 Seasonal influenza vaccine3