Immunization in pediatric patients vidyasagar


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Immunization in pediatric patients vidyasagar

  1. 1. IMMUNIZATION IN PEDIATRIC PATIENTS IMMUNITY The term immunity refers to resistance exhibited by the host towards injury caused by microorganisms and their products. Protection against infectious or pathogenetic agents is only one consequences of immune response, which in entirely is concerned with reactions of body against any foreign antibody. Immunity hence by different mates plays a significant role in normal life of an individual without which survival is almost compromised. Study of immunity has a long history where in 1718 (18th century) people used small pox infectious sites for inoculation in their children at an early age. This proved very much successful by preventing further attack of small pox in children at on older age. This began the process or method of immunization of children so as to prevent further attacks from a similar organism. 1
  2. 2. Types of immunity: Immunity against infectious agents is of different types namely: 1. Innate immunity: a) Specific Species Racial b) Non specific Individual 2. Acquired immunity: Acute Natural Artificial Passive Natural Artificial Innate immunity: Innate immunity or native immunity of an individual is the immunity, which an individual possesses by virtue of his genetic and constitutional make up. It does not depend upon the caries contact of an individuals with infectious agents or immunization. 2
  3. 3. It may be non-specific when the degree of resistance to an infection is considered in general or specific when resistance to a particular pathogen is concerned. Innate immunity is considered at the level of species, race and individual. Immunity at the level of species is shown by total or relative refractoriness to a pathogen shown by all individuals of a species. For example, human beings are resistant to infections from plant pathogens and to pathogens of animals. The mechanism of this immunity is not understood fully but may be due to changes in physiological and biochemical properties between tissues of different host species which determines whether or not the pathogen can grown in them. Racial immunity is evidenced by differences in total resistance capacities of individuals of different races. It can be seen mainly in animals. In human beings it is seen that the overall resistance of negroes is more when compared to whites. Infections like malaria are more frequently in whites when compared to negroes possibly because, the high incidence of sickling (sickle cell carcinoma) provides 3
  4. 4. resistance against malaria organisms. Each racial differences are known to be genetic in origin and by selection and in breeding possible to develop at will races that have higher degree of resistance or susceptibility to various disease pathogens. Immunity (innate) at individual level can be considered under various aspects as follows: 1. Age: Two extremes of life present with increased susceptibility to infections. The immune system in children is weak as it is still in a developing stage. In fatal life infections are reduced by immune system of mother. In younger age increased susceptibility may be due to hormonal alterations. As the age is progressed towards old age the immune system gets waned and again susceptibility to infections is increased. Hormonal Influences: Endocrine disturbances like diabetes, adrenal dysfunction, hypothyroidism etc are activated with enhanced susceptibility to infections. In all these cases immune mechanisms are compromised. The corticosteroids suppress 4
  5. 5. immune system by their action as anti-inflammatory and antiphagocytic. At the same time steroids also exhibit properties like neutralization of bacterial endotoxins. Nutrition: The relation between nutrition and immunity very complex. In general both cell mediated and humoral immunity are reduced in malnutrition. It is also seen that certain conditions may not be seen in severely ill patients. The malarial infection in very severe illness may not induce fever but when diet (nutrition) is improved it may produce fever. It is found hence that certain viruses and bacterias can not grow in cases of severe illness. Mechanism of Innate Immunity: Skin and mucous membrane: An intact skin and mucous membrane provide considerable protection against invasion by microorganisms. Healthy skin possesses bactericidal property by means of high concentration of salt in drying, sweat. The sabecious glands and long chained free fatty acidic also impart a protective action against microorganisms. 5
  6. 6. Mucosa of respiratory tract has several innate mechanisms to provide immunity. Before the air could enter the lungs starting from the point of entry of air into nasal orifices the air is filtered to remove all impurities, the larger particles are removed in nasal cavity by ciliac and mucous secretions. The smaller particles which escape from nasal cavity are removed by mucous secreted along the bronchus. Once the particles are caught they are ultimately coughed out. Any other small particles escaped through these ways are removed by phagocytes in respiratory alveoli. Mouth is constantly bathed by saliva which has several antibacterial properties. The particles in mouth are subjected to various digestive juices and ultimately digested. Strong acidic pH in stomach helps in fighting against many organisms. If organisms can survive in acidic environment these are ultimately killed in intestine when the pH of secretions increases gradually and becomes alkaline. Intestinal mucosa consists of normal microbial flora which prevents further colonization by other organisms. Conjunctiva is freed from foreign particles by the flushing action of lacrimal secretions. Tears contain 6
  7. 7. lysozymes, an antibacterial substance in them. This lysozyme is in an amount present in lacrimal fluid mainly active against gm positive non pathologic cocci, lysozymes are present in all of the tissue fluids and secretions except in C.S.F. sweat and urine. It has been found that phagocytic cells contain significant amounts of lysozyme in them to be active against majority of athogenic organisms. Flushing action of urine frees the bacteria from urethra. Antibacterial substances in blood and tissues: Complement system possesses bactericidal properties and plays an important role in destruction of pathogenic organisms that invade blood and tissues. Propordin a substance present in normal serum combines with complement an mg++ ions lysis of gm negative bacteria and also some viruses. Several other factors having antibacterial property in blood are: 1. Beta lysine – A relatively hemostable substancec active against anthrax and related bacilli. 7
  8. 8. 2. Basic polypeptides like lukins secreted from leukocytes and plakin secreted by platelets. 3. Lactic acid in muscles and in inflammatory zones. All these substances exhibit antibacterial properties. Cellular factors in Innate Immunity: Natural defence against invasion of blood and tissues by microorganisms and other foreign particles is mediated to a larger extent by phagocytic cells, which ingest and destroy them. Phagocytic cells are classified as microphages and macrophages. The microphages consist of polymorphonuclear leukocytes. Macrophages consist of wandering ameboid cells. Cells of reticuloendothelial system and monocytes. A major function of RE system is removal of foreign particles that enter the body. The phagocytes reach the site of inflammation by different chemotactic substances and ingest the foreign bodies. The bacterias are phagocytosed into a vacuole which combines with lysosyme to form phagolysosome. The phagolysosome is subjected to various lytic enzymes to destroy the organism. 8
  9. 9. Inflammation: Tissues injury or irritation initiated by the entry of microorganisms leads to inflammation which is an important nonspecific defense mechanism. The blood vessels constrict initially followed by dilatation. The processes like margination ad diapedesis and emigration of leukocytes from blood vessels to inflammatory site takes place which leads to phagocytosis. Fever an increase in overall body temperature is also a defense mechanism mainly by inhibiting in growth or destroying pathogenic organisms. Acquired Immunity: The resistance that is acquired during life of an individual is known as acquired immunity. It is different from innate immunity which is inborn. Acquired immunity is of two types namely: 1. Active immunity. 2. Passive immunity. 9
  10. 10. Active immunity: Active immunity is the resistance developed by an individual as a result of an antigenic stimulus. This involves active functioning of persons immune system leading to synthesis of antibodies and / or immunologically active cells. Active immunity sets in only after a latent period which is required for the immunologic machinery to set in motion. During the development of active immunity there is often a negative phase during which, the measurable immunity is lower than the immunity present prior to exposure to an antigen. This is seen because, during the process or period of initial exposure, the antibodies normally present are utilized for phagocytosis and therefore there is a net reduction in total immunity. Once the immunity sets in it increases rapidly and remains for a longer period of time. A second similar exposure leads to setting of immunologic response at a very faster rate and more efficiently. Active immunity is characterized by immunologic memory. This means memory of prior antigenic exposure is 10
  11. 11. retained for a longer period of time and produces a secondary type of reaction when it meets same antigen. (Active immunity is more effective and confers better protection than passive immunization). Passive Immunity: The resistance that is transmitted in a readymade form is known as passive immunity. The host immune system plays no role in providing protection. The antigenic stimulus is absent, instead, preformed antibodies are administration. Unlike active immunity, the latent period is absent. The immune actions begins almost immediately and the negative phase is absent. The immune reaction is transient and lasts for few weeks to months. This protection is seen till the passively administered antibodies are metabolized and eliminated from the body. No secondary type of reaction is seen. Instead if the same antibody is given again for the second time it is eliminated more rapidly from the body when compared to first time. This factor of immune elimination limits the usefulness of passive immunity. 11
  12. 12. The passive immunity is therefore less useful than active immunity in providing immune capacity. The only advantage being its immediate action. Active Immunity Classification: Active immunity may be: - Natural - Artificial Natural active immunity results from either clinical or inapparent infection from a parasite. A person who has recovered from these infections develops natural active immunity. Example, a person recovered from small pox, chicken pox etc. Increased resistance to poliomyelitis in individuals of developing countries due to many subclinical attacks by poliovirys in childhood. Some viral infections may give life long immunity (measles). The period of natural active immunity varies from the type of pathogen and virulence of pathogens. Some viral infections like common cold due to influenza virus may give 12
  13. 13. only a shorter period of immunity. The common cold due to influenza virus may recur due to reduction in immune response to second infection. The immunity following bacterial infection is less permanent when compared to viral infection some infections like typhoid fever provide sufficient immunity for a longer period of time. A special type of immunity called premunition is seen in syphilis. This is characterized by presence of immunity to a pathogen is seen as long as the original infection is active. Once the original infection is cured, the person becomes susceptible to infection by the same microorganisms again. Artificial Active Immunity: Immunity in children includes involves both natural active immunity and artificial active immunity. The artificial active immunity is the immunity or resistance induced by vaccine. Vaccine are the preparations of live or killed microorganisms or their products used for immunization. 13
  14. 14. The vaccine therefore are divided in to: 1. Live vaccine Bacterial Viral 2. Killed Bacterial Viral 3. Bacterial products divided vaccine – toxoids for diphtheria and tetanus. Live vaccines initiate on infection without causing any injury or disease. The immunity following live vaccine administration is similar to that following natural infection but is of a lower order. Once set, the immunity lasts for several years, but booster doses are / may be necessary. The administration of live vaccine in children /adults may be done orally, (example – sabin vaccine and poliomyelitis or parentrally. Example, Smallpox virus vaccine. Killed vaccine are generally less immunigenic than live vaccine and the protection by them lasts only for a shorter period of time. Therefore they require to be administered repeatedly, usually at least two times. The first injection is 14
  15. 15. known as primary dose and second dose is known as booster dose. killed vaccine can be again given either orally (taboral vaccine for typhoid) or parenterally. The oral route is generally not as effective as by parental route. The killed vaccine by parental route generally provide humoral antibody response. Not all the organisms are available in avirulent form. In order to overcome this if living organisms are to be present in vaccine (live vaccine) they have to be treated in such a way that the organisms loose their disease producing ability. This process is called as attenuation. The commonly used methods for this include adopting the organisms to unusual environmental condition so that they lose the ability to replicate completely in their usual host. Culturing the viruses at a temperature lower than normal is the next method. Live attenuated vaccine provoke a rapid protective response through stimulation of interfering production. Live vaccine are difficult and expensive to prepare, possibility of dangerous extraneous organisms is also seen. 15
  16. 16. Natural Passive Immunity: Natural passive immunity is the resistance passively transferred from the mother to infant /baby. In humans maternal antibodies are predominantly transferred through placenta (especially IgG) and gives immunity to the infant, human chelostrum is rich in IgA and also contribute for immunity of the featus. From about 12th week of I.U. the human embryo starts developing IgM in its body. But the IgM embryo at this stage is not active enough to combat all the infections. It is only at about after 3 months post anterior life the infant gets immune capacity independently. Till then the child utilizes immune system of mother that is transmitted to it. The transmission of antibodies from maternal to factal circulation across placenta is an active process and it is found that fectus has more concentration of antibodies than maternal circulation protection so afforded is sufficient to resist all infections during that period. Hence any infections are more common after 3 months of age. 16
  17. 17. By active immunization of a pregnant women it is possible to improve the passive immunity in infants. The recommendation of titanus tunoid vaccine prophylactically is hence of use in areus with increased tendency for neonatal titanus. Artificial Passive Immunity: Artificial passive immunity is the resistance passively transferred to a recipient by injecting antibodies. The agents used for this purpose are hyper immune animal and human sera, convalescent sera, and pooled human gamma globulin. The oldest and commonest method employed is to inject hyper immune horse sera. It is prepared by injecting appropriate antigen into horse serum. Example – Anti-tetanus serum (ATS) used for prophylaxis against tetanus infection is prepared by administering a series of doses of antigens into horse circulation. Then the blood is collected and serum is separated from blood. The antibodies are then concentrated and purified and sterilized. The main problem with animal enzymatic preparations is an increased tendency for hypersensitivity reactions. 17
  18. 18. In order to overcome this problem human sera can be utilized. Serum collected from patients convalescing from infections diseases contain high concentration of specific antibodies. Such convulsing serum is utilized for passive immunization against viral infections like measles and rubella. The main risk of using human sera is transmission of serum hepatitis. Passive immunization is utilized mainly for providing immediate and temporary protection in a non immune host having chances of infection. It is also utilized to provide resistance till active immunization is in action. Passive immunization can also be employed with active immunization and this is called as “combined immunization”. Combined immunization is indicated whenever an immediate action is required which is given by passive immunization. The immune actions remains active after words by active immunization. Paediatric or childhood is the best age at which majority of disease can be prevented by means of various 18
  19. 19. methods. Vaccination in childhood has become an inexpensive and most useful methods by which prophylaxis can be given. Since the time of introduction of vaccine there is a decline or reduction in the overall rates of infections like cholera, tuberculosis, typhoid, mumps, smallpox, tetanus and polio etc. which are most common diseases affecting in early childhood. Some of the diseases against which the immunization by vaccines is available at present are: 1. Diseases that can be prevented by environmental improvement or vaccination: - Japanese encephalitis. - TB. - Yellow fever. - Typhoid. - Rubis - Cholera - Hepatitis B (Horizontal transmission). 2. Diseases preventable only by vaccination: - Poliomyelitis. - Diphthories. - Measles. - Rubella. 19
  20. 20. - Mumps. - Purtysis. - Meningococcal meningities. - Influenza. - Chickenpox. - S.pneumonia pneumonia. - Hepatitis B (vertical transmission). Routine Vs Special Immunization: Based on prevalence and severity of a disease, safe and vaccine are preferred for routine repeated administration in infants and early childhood. Thus in India routine administration is recommended for: - Measles. - Diphthoria. - Tetanus. - Purtusis. - Typhoid fever and - Tb Robis vaccine is usually given as a post exposure prophylaxis and in more prone individuals as a pre exposure prophylaxis cholera vaccine is recommended only as a measure against epidemics. In pediatric practice immunization should be given to all susceptible individuals and this vaccine is usually taken 20
  21. 21. at an individual level. Immunization can safely be given in minor illness like diahhroea, URTI etc. In order to control the vaccine preventable disease WHO and member countries including India has established on expanded programme on immunization. Some of the Practical Aspects 1. There is no contraindication for concurrent administration of multiple vaccines like DPT, OPU, or MMR. 2. A lapse in schedule of immunization does not always necessitate reinstitution of total course. If a second hours of DPT or OPU is missed it is not necessary to reinstitute the complete course. 3. If immunization scheme of a child is unknown there is no harm in giving appropriate vaccines again. 4. Dose reduction is not appropriate since it may cause in appropriate immunologic response, increased dose is also not indicated which may cause side effects. 5. Live vaccines of all types and BCG should not be given in individuals with congenital disorders of immune 21
  22. 22. system. These should also be avoided in children who are taking steroids for rt since these causes immunodepression. A short course of low dose of steroids is not a contraindication for vaccines. Vaccines of this kind should also be avoided in children with active symptoms of AIDS. 6. Children suffering from neurologic disorders or with previous history of convulsions are at a higher risk for purtuse vaccine. 7. Active immunization after exposure to disease is indicated in: - Rabies. - Measles (within 3 days of exposure). - Hepatitis and - Tetanus. Immunization schedule: Various immunization schedules are recommended in order to protect a child from infections. Some of the immunization schedules are: 22
  23. 23. National Immunization schedule : The first visit may be made when the child is 6 weeks old. The recommended schedule is given in next page. Beneficiaries Age Vaccine No. of doses Route of administration Infants 6 weeks to 9 months DPT POLIO BCG 3 3 1* Im Oral Intradermal 9-12 months Measles Subcutaneous Children 16-24 months DPT Polio 1* 1** Im Oral 5-6 years DT Typhoid 1@ 2 Im Subcutaneous 10 years Tetanus tonoid Typhoid 1@ 1@ Im Subcutaneous 16 years Tetanus T Typhoid 1@ 1@ SC SC Pregnant women 16-36 months T-T 1@ Im * For institutional deliveries BCG should be given at birth. ** Booster dose @ 2 doses if not vaccinated 1 Intervals between two doses should not be less than one month 2 minor illness is not a contraindication. 23
  24. 24. WHO EPI schedule This strongly recommended institution of BCG and polio vaccines at birth or at the time of initial contact, in countries where Tb and polio have not been controlled. In all countries immunization for polio is safely started at 6 weeks of age along with DPT. The given schedule is as follows: Age Vaccine Birth BCG, oral polio 6 weeks DPT, oral polio 10 weeks DPT, oral polio 14 weeks DPT, oral polio 9 months Measles Diphtheria: Common disease in India, which has sufficient number of antibodies circulating in maternal circulation. The antibodies are easily to crossed across placenta and fetal immunity is cortered till birth and for first 3 months. The vaccine is given as a triple vaccine DPT or D.T. 24
  25. 25. Primary dose consists of 3 doses at 4, 6 and 8 weeks of birth, I booster dose is given during second year of age, at 18 months. A second booster dose is given at 5 years of life. Pertusis: - Given as triple vaccine DPT. - Since protective antibodies cannot cross placenta vaccination is a must. - 3 doses are recommended at 9-8 weeks of internal from 1-3 months of age. - Common adv reactions: o Local pain irritability. o Screming for a prolonged time. o Convulsions in some cases. - Not recommended in neuromuscular disorder and patients with convulsive history. Tetanus: - Neonatal tetanus is an important cause of mortality in many developing countries. 25
  26. 26. - Since there is no natural immunity, the unimmunized mothers fail to transfer the antibodies to their infants against tetanus toxin. - Immunizing pregnant women with T toxoid of great value. - Vaccination against TT is given as DPT or DT or TT alone. - Booster dose is given at 18 months, 5 years and 10 years and thereafter 6 months intervals. BCG: - Bacillus culmette guerin is an attenuated strain of mucobacterium tuberculosis. It is a line vaccine. - In order to maintain its potency the vaccine is supplied at a temperature of 4°C at which the potency remains satisfactory for several months. Since no immunity is transferred from mother to infant BCG has to be administered after birth. The vaccine is given intradermally above the deltoid muscle. After 2-3 weeks a papule develops at the site of injection which ultimately heals by scarring. 26
  27. 27. Adverse reaction being - Regional lymphnods with infrequent dressing. Measles: - Live attenuated measles virus is used as a vaccine. - Vaccine stored at 4-8°C can be used for 1 year. - Given by S.C. or Im route. - Recommended minimum age is nine months. Because before this period maternal antibodies circulating in fetal blood neutralizes the virus in live vaccine. Mumps: - Vaccine consists of live attenuated mumps. - Given as a trivalent vaccine with measles and rybella. - Mumps vaccine of MMP may be given after 12-15 months of age. Rubella: - Immunization is given solely to prevent congenital rubella. - Two approaches are recommended. o Either to selectively immunize girls. o Immunize girls and boys simultaneously. 27
  28. 28. - In India incidence of rubella is not known. - Prophylaxis starts at on age of 12 months. Rabies: - Cause (explain). - Since the incubation period is more post exposure vaccination is safely given for infected individual. - It employs administration of killed rabies virus vaccine. - Modified semple’s vaccine is one vaccin for rabies administered S.C. over anterior abdominal wall for 7- 14 days. In some cases booster doses are also required. - Modern vaccine have advantage over semples vaccines in that no neurological symptoms are seen. - These vaccine are given Im or Sc on 0, 3, 7, 14, 30 and 90 days. Typhoid: - Employs standard acetone killed salmonelle typhi infections. 28
  29. 29. - Primary immunization requires two S.C. doses at 4 week intervals. In out breaks the period may be reduced to 1 week also. - Dose is 5ml for children of 10 years. - Booster doses once in 3 years are recommended. Cholera: - Suspension of heat killed vibrio cholera is used as vaccine for cholera. - Recommended rarely and only in outbreaks of the disease. - Given either ID, Im or Scly. Hepatitis B A purified suspension of 22 nanometer particles bearing H.B. virus surface antigens found in some chronic carriers are used as vaccines. Any residual virus is inactivated by formaldehyde and heat. Recently a genetically engineered recombinant vaccine is available. In pediatrics its main use is in preventing mother to transmit the disease to infant neonates borned to carrier 29
  30. 30. mothers should given Human anti hepatitis B globulin (AHBG) and a course of vaccines according to recommendation by manufacturers. 30