Health Topics: /Immunization

    Immunization is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body's own immune system to protect the person against subsequent infection or Immunization is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body’s own immune system to protect the person against subsequent infection or disease.

    Immunization is a proven tool for controlling and eliminating life-threatening infectious diseases and is estimated to avert between 2 and 3 million deaths each year. It is one of the most cost-effective health investments, with proven strategies that make it accessible to even the most hard-to-reach and vulnerable populations. It has clearly defined target groups; it can be delivered effectively through outreach activities; and vaccination does not require any major lifestyle change.

    Passive and active immunization

    Medical student participating in a polio vaccine campaign in Mexico

    Immunization can be achieved in an active or passive manner: vaccination is an active form of immunization.

    Active immunization

    Active immunization can occur naturally when a person comes in contact with, for example, a microbe. The immune system will eventually create antibodies and other defenses against the microbe. The next time, the immune response against this microbe can be very efficient; this is the case in many of the childhood infections that a person only contracts once, but then is immune.

    Artificial active immunization is where the microbe, or parts of it, are injected into the person before they are able to take it in naturally. If whole microbes are used, they are pre-treated.

    The importance of immunization is so great that the American Centers for Disease Control and Prevention has named it one of the "Ten Great Public Health Achievements in the 20th Century".[1] Live attenuated vaccines have decreased pathogenicity. Their effectiveness depends on the immune systems ability to replicate and elicits a response similar to natural infection. It is usually effective with a single dose. Examples of live, attenuated vaccines include measlesmumpsrubellaMMRyellow fevervaricella,rotavirus, and influenza (LAIV).

    Passive immunization

    Passive immunization is where pre-synthesized elements of the immune system are transferred to a person so that the body does not need to produce these elements itself. Currently, antibodies can be used for passive immunization. This method of immunization begins to work very quickly, but it is short lasting, because the antibodies are naturally broken down, and if there are no B cells to produce more antibodies, they will disappear.

    Passive immunization occurs physiologically, when antibodies are transferred from mother to fetus during pregnancy, to protect the fetus before and shortly after birth.

    Artificial passive immunization is normally administered by injection and is used if there has been a recent outbreak of a particular disease or as an emergency treatment for toxicity, as in for tetanus. The antibodies can be produced in animals, called "serum therapy," although there is a high chance of anaphylactic shock because of immunity against animal serum itself. Thus, humanized antibodiesproduced in vitro by cell culture are used instead if available.Immunizations, or vaccines as they're also known, safely and effectively use a small amount of a weakened or killed virus or bacteria or bits of lab-made protein that imitate the virus in order to prevent infection by that same virus or bacteria.

    When you get an immunization, you're injected with a weakened form of (or a fragment of) a disease. This triggers your body's immune response, causing it to either produce antibodies to that particular ailment or induce other processes that enhance immunity.

    Then, if you're ever again exposed to the actual disease-causing organism, your immune system is prepared to fight the infection. A vaccine will usually prevent the onset of a disease or else reduce its severity.

    Why Should Someone Get Immunized?

    The goal of public health is to prevent disease. It's much easier and more cost-effective to prevent a disease than to treat it. That's exactly what immunizations aim to do.

    Immunizations protect us from serious diseases and also prevent the spread of those diseases to others. Over the years immunizations have thwarted epidemics of once common infectious diseases such asmeaslesmumps, and whooping cough. And because of immunizations we've seen the near eradication of others, such as polio and smallpox.

    Some vaccines need to be given only once; others require updates or "boosters" to maintain successful immunization and continued protection against disease.

    Which Immunizations Do My Children Need?

    Because proof of immunization is often a prerequisite for enrollment in school or day care, it's important to keep your children up to date on their vaccines. The benefit of doing so is that your children will be protected from diseases that could cause them serious health problems. The recommended immunizations for children 0-6 years of age include:

    At one time or another, each of the diseases addressed by these vaccines posed a serious health threat to children, taking their lives by the thousands; today most of these diseases are at their lowest levels in decades, thanks to immunizations.

    It's important to keep your child's immunizations on schedule and up to date, but if your child misses a scheduled dose he or she can "catch up" later.The complete updated schedule of immunizations for children ages 0-18 can be 

    What About Immunization Side Effects?

    Today, vaccines are considered safe. As with any medication, they can have side effects. In most cases these are usually mild. Most common minor reactions to an immunization are:

    • Soreness or redness around the injection site
    • Low-grade fever

    Side effects like these usually disappear in a few days. In extremely rare instances a high fever, in excess of 104 F, can occur with a vaccine.Fevers like this will not harm your children, but they can make them uncomfortable and upset.

    Children have also been known to have serious allergic reactions to a vaccine. These usually happen very soon after getting the vaccine, and doctors' offices are well equipped to handle such reactions. If you think your child has or may have an allergy to any component in a vaccine, be sure to share that information with your doctor.

    Medical providers agree that the proven preventive benefits of vaccines far outweigh the risks of the minimal side effects associated with them. More information about vaccine side effects and precautions can be found in the CDC's brochure Parents Guide to Childhood Immunizations.

    How Effective Are Immunizations?

    Vaccines are very effective at preventing disease, but they don't work all the time. Most of the recommended childhood immunizations are 90%-100% effective, according to the CDC.

    However, for reasons that are not completely understood, sometimes a child will not become fully immunized against a disease after receiving a vaccine. This is all the more reason to get children vaccinated. Children in whom the vaccine is 100% effective protect those few who have not been completely immunized -- lessening everyone's chance of exposure to the disease.

    Even in cases where a vaccine has not given your child 100% immunity, the symptoms -- if your child is exposed to an infectious disease -- will still usually be milder than if he or she had not been immunized at all.

    Vaccine Myths and Misinformation

    Here are important answers to three common misconceptions about vaccines.

    Misconception #1: "We don't need to vaccinate against rare diseases."

    Few parents today have even heard of all of the diseases we vaccinate against, let alone seen a case of the measles, diphtheria, or whooping cough.

    Vaccine Myths and Misinformation continued...

    This leads some to ask, "Why am I giving my child a vaccine against a disease that doesn't even exist?"

    The answer is that it's the vaccines that keep these diseases so rare. Avoiding having your child immunized because of myths and misinformation about vaccine safety puts your child -- and public -- at risk. In communities where vaccine rates have dropped, these infectious diseases have quickly returned.

    Misconception #2: "The preservative thimerosal makes vaccines risky."

    Another concern about vaccines involves the use of a mercury-based preservative called thimerosal.

    The purpose of vaccination is to produce immunity. Immunity means the presence in a person's body of cells and substances known as antibodies that can produce a protective immune response.
    The purpose of this review is to revise and update on the evolving immunization schedule at national and at global level. Good vaccination practices begin shortly after birth. The WHO estimated that immunization currently averts an estimated 2 to 3 million deaths every year apart from societal burden & medical costs. For each birth cohort vaccinated in the United States, approximately 20 million illnesses are prevented, along with 40,000 deaths. 
    The Advisory Committee on Vaccines and Immunization Practices (ACVIP) of the Indian Academy of Pediatrics (IAP) has recently (2014) updated immunization schedule for children aged 0 through 18 years. This was based on recent evidences for licensed vaccines that are incorporated in our clinical practices in India (Table 1). 

    Table 1: Recommendation for IAP Immunization - updated 2014 Schedule
    Birth doseBCG, OPV-zero , HepB1these vaccines given to all newborns before hospital discharge
    6 weeksDTwP1, IPV1, Hib1, PCV1, HepB2DTaP combinations should preferably be avoided for the primary series.
    10DTwP2, IPV2, Hib2, PCV2, Rota1If RV1 is chosen, the first dose should be given at 10 weeks. Only 2 doses of RV1 are recommended at present
    14DTwP3, IPV3, Hib3, PCV3, Rota2(2nd dose Rotarix –final)
    6 monthsOPV1, HepB3 
    9 monthsOPV2 , MMR1Measles-containing vaccine ideally should not be administered before completing 270 days or 9 months of life. The 2nd dose must follow in 2nd year of life.
    9-12 monthsConjugated Typhoid vaccineCurrently, two typhoid conjugate vaccines, Typbar-TCV and PedaTyph available in Indian market. Should follow a booster at 2 years of age
    12 months HepA1One of the 2 doses of inactivated now or a-single dose for live attenuated H2-strain HepA vaccine now recommended
    15 monthMMR2, varicella1 , PCVbThe risk of breakthrough varicella is lower if given 15 months onwards
    16 to 18 months DTwP b1 or DTaP b1 
    IPV b1 , Hib b1
    DTwP or DTaP booster (4th dose) may be administered as early as age 12 months, provided at least 6 months have elapsed since the third dose. Considering a higher reactogenicity of DTwP, consider DTaP for the boosters.
    18 months to 2yrsHepA2, TyphoidbAlso suggesting only single dose for live attenuated H2- strain HepA vaccine
    4 -6 yrsDTwP b2 or DTaP b2 ; OPV3 Varicella2 and Typhoid b2nd dose varicella can be given at any time 3 months after the 1st dose
    10 -12 yearsTdap or Td, 
    HPV series to begin
    Tdap is preferred to Td ,followed by every 10 years
    HPV : 2 or 3 doses > 9 yrs. & older

    One should follow and adhere to the regional health authority & Institutional immunization policy that are principally derived from the Centers for Disease Control and Prevention (CDC &P) and the WHO. The immunization schedules are intermittently revised and updated; these programs are supported by the Global Alliance for Vaccines and Immunization (GAVI) at the global level. 
    The Advisory Committee on Immunization Practices (ACIP) of the CDC & P, has now updated to reflect the 2016 immunization schedules for the use of vaccines for children and adolescents. The schedules are approved by the American Academy of Pediatrics (AAP), the American Academy of Family Physicians (AFP), and the American College of Obstetricians and Gynecologists (ACOG). (Table 2) 

    Table 2: General Recommendation from ACIP/CDC from Newborn to 18 yrs. of age
    VaccinesBirth2 mons4 mons6 mons9 mons12 mons15 mons18 mons2 -3 yrs.4-6 Yrs.11-12Yrs.
    HepB1st2nd 3rd
    Rota oral RV1 or Rv5 Rv1 or Rv5Rv1 or RV5        
    DTaP 1st2nd3rd  4th 
     5thTdap Q 10 yrs.
    Hib 1st2nd  3rd or 4th3rd or 4th    
    Pneumo 1st2nd3rd 4th4th    
    Polio: IPV <18y 1st2nd 3rd3rd   4th 
    Influenza (IIV)   yearly       
    MMR     1st 
    Varicella     1st 
    HepA        2 dose series  
    Meningo(MCV4)          2 dose
    HPV          3 dose series

    Combination vaccines
    Combination vaccines are necessary and important for the continuing success of our immunization program, especially when more vaccines are added to the already crowded immunization schedule. However, the multiplicity of competing vaccine products, with various overlapping antigen menu and subtle immunologic differences, may be confusing to the busy practitioner. Combining vaccines that target children immunization may expand immunization opportunities and effectiveness. However, offering new choices may not necessarily translate into simpler solutions at the practical level. The combo’s aspects of immunization schedules is not included in this review.


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