Vaccines, Vaccination and Immunisation


Immunization is a successful use of immunotherapy to treat many infectious diseases by stimulating the immune system to produce specific antibodies or specific lymphocytes to fight off pathogens and, more recently, protect against malignant tumors.  This immunotherapy creates an immunological memory that can be long-lasting. The current immunizations protect against diphtheria, tetanus, pertussis, poliomyelitis, measles, mumps, rubella, pneumococcal pneumonia, smallpox, sepsis, meningitis, hepatitis B, varicella-zoster, tuberculosis, cholera, diarrhea caused by rotavirus, salmonellosis, and dengue.

However, the development of vaccine technology in recent years, the emergence of HIV, SARS, avian influenza, Ebola, and Zika emphasizes the need for global preparedness for a pandemic.

Mechanism of Action

Live vaccines are more effective than killed vaccines because they retain more antigens of the microbes. However, toxoids, including those that cause tetanus and diphtheria, are the most effective bacterial vaccines because their effect is based on inactivated exotoxins that stimulate strong antibody production. Subunit vaccines, including hepatitis B, meningococcal, and Hemophilus influenzae B vaccines, are effective when conjugated to carrier proteins such as tetanus toxoid. Vaccinologists produce subunit vaccines either by recombinant DNA technology or by antigen purification from different bacterial strains.

A short video edition on Vaccines and Immunisation


Most human vaccines are administered by injection, although this approach is risky in the developing world, where injections can transmit diseases such as HIV infections. Live vaccines can be given orally but not killed vaccines. Alternatively, the use of the oral route and other mucosal surfaces have been explored as an immunization route. For example, polio vaccination underwent a successful implementation via the oral route.

Adverse Effects

Attenuated vaccines have several potential safety issues, including:

  • Hypersensitivity to viral antigens (measles)
  • Hypersensitivity to egg antigens (mumps)
  • Persistent infection (varicella-zoster)
  • In an immunodeficient patient, it may cause severe disease (BCG)

Killed vaccine safety issues include:

  • Yeast contaminant (hepatitis B)
  • Contamination with animal viruses (polio)
  • Endotoxin contamination (pertussis)


All vaccines have as contraindications severe allergic reactions (e.g., anaphylactic reaction) after a previous dose or to a vaccine component. DTaP should contraindicate if the child develops encephalopathy within seven days of administering a prior dose of DTP or DTaP and after ruling out other causes of brain illness. Hepatitis B vaccine contraindicates in patients with hypersensitivity to yeast. Hib vaccine is contraindicated in infants aged less than six weeks.

MMR vaccine is avoided in those with a known severe immunodeficiency due to lymphoid malignancies, congenital cause, chemotherapy, family history of immunosuppression, and in patients with HIV/AIDS. Rotavirus vaccine must contraindicate in children with a history of intussusception, and it should use with precaution in altered immunocompetence, other than severe combined immunodeficiency disorder. Both varicella and zoster vaccines contraindicate in immunocompromised host and pregnancy. Live-attenuated influenza virus vaccine should be avoided when in the previous 48 hours, a patient has taken influenza antiviral medication; dosing should proceed with caution in patients who developed Guillain-Barré syndrome within six weeks after a prior dose of influenza vaccine and in patients who have asthma.


Most vaccines have adverse reactions, as is the case with any drug or medication. For example, BCG vaccination may provoke fever, vomiting, hematuria, lymphadenitis, and redness at the injection site. Hib vaccine has few adverse reactions, and none of them are dangerous. These reactions include redness, warmth, swelling, and fever over 101 F (38.3 C). A rare and lethal adverse reaction secondary to vaccination is the Guillain-Barre syndrome.


Anaphylactic reactions are examples of allergic reactions that can affect individuals that are vaccinated. They can be treated with aqueous epinephrine 1 to 1000 dilution intramuscularly (IM), 0.01 mL/kg/dose. The adult dose can range from 0.3 mL to 0.5 mL. Optional treatment is the use of an H1 antihistamine for skin reactions (hives or itching). It can administer diphenhydramine (either orally or IM). Inject a dosage of 1 to 2 mg/kg every 4 to 6 hours, up to 50 mg) or hydroxyzine 0.5 to 1 mg/kg every 4 to 6 hours up to 100 mg. 

The dosage of epinephrine can repeat every 5 to 15 minutes for up to 3 doses, depending on the clinical picture. Record the patient’s reaction, the medications, and the health care provided to the patient, and the name of the personnel who administer the drug.

Additional Information

An interprofessional team of scientists and healthcare professionals produces vaccines. Once the FDA approves a vaccine, it can be manufactured on a large scale by biotechnologists. In the healthcare setting, a pediatrician or family doctor orders or restricts immunization in a child. Nurses or pharmacists often carry out the immunization procedure. Side effects of the vaccines can be monitored by primary care physicians, pharmacists, and nurses, and when adverse events occur, they need to be communicated to the rest of the team. The emergency service plays a vital role in allergic reactions, including anaphylaxis, where it brings together primary health care services with secondary or tertiary healthcare institutions. The treating clinician, along with nursing and pharmacy, needs to manage the patient’s vaccine records and ensure that they remain up to date. Only with this type of collaborative interprofessional effort can vaccinations be as effective as they need to be in preventing disease, both for the individual patient as well as in the public health arena for transmissible pathogens. 


Justiz Vaillant AA, Grella MJ. Vaccine (Vaccination) [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:

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