| IAP Guidebook on Immunization |
| Table of Contents | Committee on Immunization | |
|
||
| UIP Vaccines We will now consider in detail each vaccine recommended in the UIP Schedule. For convenience these vaccines are called UIP Vaccines. BCG Vaccine The pathogenesis of tuberculosis and immunity in infected persons are very complex phenomena. Infection with BCG although very localised and with attenuated bovine tubercle bacilli, induces cell mediated immunity and some protection. The protection is maximum against the hematogenous spread of M. tuberculosis, which results in miliary TB or TB meningitis. The vaccine is supplied as a lyophilised (freeze-dried) preparation, which is to be reconstituted with the recommended diluent. Sterile normal saline may be used for reconstitution. In liquid phase the organisms tend to be temperaturesensitive and the potency may drop with increasing time. Moreover, the vaccine contains no antibacterial substance, hence bacterial contamination may occur with repeated entry into the vial and several hours after reconstitution. Therefore, once reconstituted, the vaccine should be used within 4-6 hours. The injection of BCG should be strictly intradermal, using special needle and syringe capable of clearly measuring 0.05 ml / 0.1 ml and delivering such small volumes without loss in the ‘dead space’ of the syringe nozzle. The convex aspect of the left shoulder is preferred so that inspection for BCG scar may be made easy. The injected site shows no change for several days. The bacterial multiplication leads to the development of a papule, which often heals after ulceration. The evolution of this lesion, upto healing with scar, may take upto 6- 12 weeks. In the absence of local scar by 12 weeks BCG vaccination may be repeated. Although there is no strict upper age limit for BCG, the most benefit is obtained by inoculation in infancy, especially in neonates. Summary : BCG Vaccine
Oral Polio Vaccine The oral polio vaccine is a suspension of over 1 million particles of polioviruses type 1, 2 and 3 together. It is supplied with a stabilizing agent, namely magnesium chloride. Therefore the potency is quite stable under refrigeration or freezing. Several cycles of freezing and thawing do not reduce the potency. When OPV is given by mouth, the vaccine viruses go through the stomach and reach the intestines where they must establish infection ( = vaccine virus take) before an immune response may occur. The viruses survive the acidity of the stomach. However, for reasons not clearly understood, the ‘take’ rate is relatively low in our children. For the above reason, multiple doses of OPV are necessary before 90 – 95% of children develop immune responses to all 3 poliovirus types. It is for this reason that the IAP recommends at least 4 routine doses of OPV, during infancy and 2 more repeat doses at 15 – 18 months and 5 years. In addition to the “Routine OPV doses”, “Pulse OPV doses every year on National Immunization days (NID’s) till the age of 5 years are also mandatory. In order to ensure that vaccinated children do not participate in the chain of transmission of wild (pathogenic) polioviruses, a high level of gut immunity should be induced in them. For this reason also multiple doses of OPV are necessary. Eradication is defined as no case of paralytic poliomyelitis by wild polio virus in last 3 calendar years along with absence of wild polio virus in the community, where excellent clinical and virological surveillance exists and the coverage of routine OPV is more than 80%. Polio elimination is defined as Zero cases of paralytic poliomyelitis by the wild polio virus in one calendar year with other criteria same as in eradication.
In developing countries with high (pre-immunization era) incidence of polio, such as in India, 3 or 4 doses of OPV given to even 90% or more infants, did not result in polio eradication. In such countries with routine immunization of 4-6 doses of OPV and a near 100% coverage during annual pulse immunization - Pulse Polio Immunization, (PPI) will be necessary to achieve eradication. Surveillance must detect all cases of Acute Flaccid Paralysis (AFP), report them and investigate for poliovirus aetiology. When any poliovirus is detected it should be examined by genomic analysis to identify it as wild poliovirus and to distinguish from vaccine strain of poliovirus, to facilitate recording the incidence of Vaccine Associated Paralytic Poliomyelitis (VAPP). Why Pulse Polio? On National Immunization Days (NID’s), pulse doses of oral polio vaccine has to be administered, as simultaneous feeding of the vaccine to all susceptible infants and children, would produce immunity to all and prevent wild poliovirus to multiply in the gut. Thus, wild polio virus cannot grow in susceptive host. Therefore, it is mandatory to administer all recommended doses in NID’s so that no wild poliovirus remains in the circulation. Injectable Killed Polio Vaccine (IPV) IPV is formaldehyde killed poliovirus grown in monkey kidney cell/human diploid cells containing 20, 8 & 32 D antigen against type 1, 2 and 3 poliovirus respectively. It is highly immunogenic. Seroconversion is 90-95%, after 2 doses and 99% after 3 doses. It produces excellent humoral immunity as well as local pharyngeal and possible intestinal immunity. The vaccine is very safe. However, it is not available at present in the Indian market for routine use and is licensed only for use in immunocompromised children. Summary: Oral Polio Vaccine
 Summary: Injectable (Killed) Oral Polio Vaccine
DPT Vaccine The combination of diphtheria toxoid, whole cell killed pertussis vaccine and tetanus toxoid is popularly known as the triple antigen. While the two toxoids are highly immunogenic and antibodies to them are almost completely protective, the pertussis vaccine, given in 3 doses, has a protective efficacy of about 70-80% only. Moreover, local (pain and redness) and systemic (fever) side effects of the DPT are almost entirely due to the pertussis component. The whole cell pertussis vaccine was suspected to induce a neurological reaction in very rare instances; however there has been no conclusive proof for this. Convulsions following DPT vaccine are rare, and when they do occur, they may be either quite benign (perhaps induced by high fever), or they may be the earliest signs of some incipient neurological disease in the infant. For these reasons, progressive neurological diseases are the only contraindication to first dose of DPT immunization. Severe adverse reactions in the form of anaphylaxis and encephalopathy occurring within 7 days to the earlier dose are contraindications for subsequent doses of DPT. They should be given DT only. The DPT must be injected intramuscularly and the preferred site is the anterolateral aspect of the thigh. The gluteal region is better avoided for 2 reasons. Occasionally the needle (and the vaccine itself) hits the sciatic nerve, causing injury, which may result in foot-drop or even more extensive paralysis. Secondly, the vaccine may be deposited in the fat pad adjacent to the muscle tissue; in that case the immune response is likely to be less than what would occur after true IM injection. This phenomenon has been shown to be important in the case of HB and rabies vaccine; although not shown directly with DPT, it is better to adhere to the principle of no IM injection gluteally. How many doses of DPT should a child receive? As far as tetanus is concerned, life-long immunity is necessary. Therefore at least 5 doses are recommended during the preschool age followed by boosters at 10 and 16 years of age. Regarding Diphtheria, no boosters are generally given in our country beyond 5 years. Hence 5 doses are important. The UIP recommends 4 doses of pertussis vaccine – 3 during infancy and the fourth during the second year of life. The need for continued protection against whooping cough in adolescents and adults is increasingly being recognised. Therefore IAP recommends the 5 opportunities available to give 5 doses of pertussis vaccine also. Hence, while UIP recommends DT vaccine at 5 years, IAP recommends DPT vaccine. Summary: DPT Vaccine
Tetanus Toxoid The reasons for TT at 10 and 16 years were given earlier. After completing the full course of 7 doses, there is no need for additional doses during pregnancy, at least for the next 10 years. Thereafter a single booster would be sufficient to extend immunity for another 10 years. For pregnant women who have not had previous immunization, at least 2 doses should be given during pregnancy so that protective antibody would be transferred to the infant in order to prevent neonatal tetanus. Summary: Tetanus Toxoid
Guide to Tetanus Prophylaxis In Routine Wound Management  ** Yes, if more than 10 years have elapsed. *** Yes, if more than 5 years have elapsed. For children less than 7 years, DPT is given and above 7 years TT or Td (if available). Tetanus Immunoglobulin (TIG) It is a liquid or freeze-dried preparation containing immunoglobulins, mainly IgG obtained from plasma or serum containing specific antibodies against the toxin of Clostridium tetani. Adverse Effects: Local pain, fever, flushing, headache and chills may occur. Indications: Subjects already sensitized with serums of animal origin, existence of prior or present allergic manifestations (asthma, eczema, etc). Burns, injuries, open and compound fractures. Unimmunised or inadequately immunised mothers. Dosage: Prophylaxis 250 – 500 I.U. Intramuscular. Therapeutic : Tetanus neonatorum 500 – 1000 I.U. intramuscular or 250 I.U. intrathecal. In adults and children 500 – 1000 I.U. intramuscular and / or 250 – 500 I.U. intrathecally. Td Vaccine (Tetanus, Diphtheria Toxoid) Td which contains usual dose of tetanus toxoid and only 2 units of diphtheria toxoid if available, is more appropriate which would prevent diphtheria, in addition to tetanus and is given at 10 years and 16 years and then every 10 years thereafter. Measles Vaccine The Measles vaccine consists of live attenuated Measles virus, developed by Enders, in 1960. The original virus strain was isolated from a child by the name Edmonston; therefore the virus strain was also named Edmonston. After attenuation it was called Edmonston B; this virus strain was not fully attenuated. Therefore several strains of further attenuated Edmonston B was developed by various investigators. Such strains in use as Measles vaccine are Schwarz, Moraten, Edmonston-Zagreb etc. In liquid suspension the vaccine virus is very heat-labile; in the freeze-dried state the shelf life of the vaccine is one to two years, or even longer. The vaccine may be stored frozen or refrigerated. But, after reconstitution, the vaccine should be injected within 4-6 hours. During such interval the liquid vaccine should be kept cold, either in the refrigerator or vaccine carrier. The Measles vaccine does not contain any antibacterial preservative. Therefore, strict aseptic technique should be used when entering the vial. If the vaccine gets bacterial contamination, bacteria may multiply, especially if liquid vaccine is kept at room temperature or if stored for longer periods. Such negligent practices have led to staphylococcal sepsis/toxic shock syndrome in rare instances. Unused vaccine should, therefore be discarded after 4-6 hours. The vaccine should be injected subcutaneously. The preferred site is right upper arm; this is only for uniformity. It can also be injected over the anterolateral thigh, but subcutaneously. The age distribution of natural Measles, in unimmunised children, vary from place to place and from time to time. While most infants are protected from measles by the maternal antibodies upto 6-8 months, infants are susceptible to the disease from 9 months onwards. If Measles vaccine is given in the presence of measurable titres of maternal antibody, the vaccine viruses are neutralised and the child does not respond with antibody. In order to achieve the best balance between these competing demands of early protection and high sero conversion, 9 months of age is recommended as the ideal, in our country. 9 months means 270 days or more. In case of an outbreak (or impending outbreak) infants completed 180 days (6 months) may be given the vaccine, provided such infants (given vaccine below 9 months) are revaccinated after at least 3 months of interval. Being a live attenuated virus vaccine, it results in actual infection and multiplication of viruses within the body. This infection mimics the wild Measles virus infection, except, (a) the disease Measles is either totally absent or may occur in a very mild form and (b) the infection does not spread from the vaccinated child to anyone else. The response to the infection may present as a short fever, of 2-3 days, starting from about 5-10 days after immunization. We could consider this as the “incubation period”, which is shorter by about 4 days than the incubation period of measles itself. In some infants/children, the fever may be high enough to cause febrile convulsions. Some 2-5% of children may have a few spots of rash, visible on fair skin, but often missed on darker skin. Since the fever is expected, parents should be alerted. The child should be examined if the fever is longer than 3 days or if other symptoms suggestive of an unrelated illness are present. Paracetamol may be given to control/reduce fever. Being a live attenuated virus vaccine, it results in actual infection and multiplication of viruses within the body. This infection mimics the wild Measles virus infection, except, (a) the disease Measles is either totally absent or may occur in a very mild form and (b) the infection does not spread from the vaccinated child to anyone else. The response to the infection may present as a short fever, of 2-3 days, starting from about 5-10 days after immunization. We could consider this as the “incubation period”, which is shorter by about 4 days than the incubation period of measles itself. In some infants/children, the fever may be high enough to cause febrile convulsions. Some 2-5% of children may have a few spots of rash, visible on fair skin, but often missed on darker skin. Since the fever is expected, parents should be alerted. The child should be examined if the fever is longer than 3 days or if other symptoms suggestive of an unrelated illness are present. Paracetamol may be given to control/reduce fever. Summary: Measles Vaccine
|