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Last updated: June 8, 2021

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Vaccination is a very effective measure for providing immunity to many infectious diseases. The discovery of vaccines played a central part in the eradication of smallpox and helped significantly reduce the incidence of potentially severe diseases such as poliomyelitis and measles. Live vaccines (attenuated, i.e. noninfective pathogens) or inactivated vaccines (subunits or complete pathogens) are used to achieve active immunization, which enables the host's immune system to build up a sustained immune response to specific pathogens. The immune response may be measured and quantified by assessing the antibody titer. In the event of potential disease (e.g., after exposure to high-risk pathogens), if the immune system is unable to produce sufficient antibodies fast enough, passive immunization can offer immediate short-term protection via direct injection of pooled antibodies for many conditions. Modern vaccines are usually well-tolerated, and adverse events are rare. However, the intervals between vaccine administration and possible contraindications must be considered.

For CDC vaccination recommendations, see “Immunization schedule.”

  • Vaccine
    • A product (e.g., dead or weakened organism) that provides immunity from a disease
    • May be administered through injection, orally, or nasally
  • Vaccination: administration of a vaccine that induces an active immune reaction in form of cellular and/or humoral response, providing immunity against a pathogen
  • Immunization
    • The process by which a person becomes protected from a disease
    • Vaccines and recovering from some infections cause immunization.


  • Herd immunity: Once a certain percentage of the population has received immunization, non-vaccinated individuals (e.g., children too young to receive vaccination) will also be protected.
    • Mass vaccination: Vaccination of a large number of people in the shortest possible time after the outbreak of an epidemic, with the goal of herd immunity.
  • Eradication of disease
    • High immunization rates over prolonged periods of time can achieve eradication of certain diseases. [2]
    • To date, only two diseases have been eradicated by human efforts: smallpox (1980) and rinderpest (2011).
  • Lower incidence and associated risks: The Haemophilus influenzae type b (Hib) vaccine has decreased the number of cases of invasive Hib disease (e.g., pneumonia, bacteremia, meningitis, epiglottitis, infectious arthritis) in children younger than 5 by more than 99%. [3]

Passive immunization Helps Beat The Disease Rapidly:” HBV, Botulinum, Tetanus, Diphtheria, and Rabies are indications for passive immunization.

Current vaccination recommendations for the US can be found in the “Immunization schedule.”

TYler And Paul Burnt their INFamous ROasted YELLOW-RUBy CHICKEN MEAt Very MUch”: TYphoid, Adenovirus, Polio, BCG, INFluenza, ROtavirus, YELLOW fever, RUBella, CHICKENpox, MEAsles, Varicella, and MUmps are live attenuated vaccines.


Whole vaccines Fractional vaccines
Protein-based Polysaccharide-based
  • Whole inactivated or dead pathogens (using chemicals or heat) that are unable to replicate
  • Surface epitopes remain unchanged, since they are important for triggering an adequate immune response.
  • Cause a weaker immune response, but are considered to be safer than live vaccines
Available vaccines
Mechanism of action
Special considerations
  • Not consistently immunogenic in infants

“Beware of Hepatitis A on your TRIP:” Hepatitis A, Typhoid fever, Rabies, Influenza, and Poliomyelitis.


  • Common adverse effects [11][12][13]
    • Affects ∼ 1/3
    • Usually begin within the first 48–72 hours after administration and last 1–2 days
    • Symptoms
    • Live attenuated vaccine: can cause mild form of the disease, usually appearing within 1–3 weeks of administration; : usually caused by replication of the attenuated vaccine strain
  • Rare adverse effects

There is no link between autism and vaccines or their ingredients. [14][15]

All children must be immunized with the standard doses of vaccines according to their chronological age; doses should not be adjusted to weight or height.


Vaccinations in preterm infants

  • Preterm infants should receive all recommended vaccinations according to chronological age unless contraindicated.

Vaccinations in HIV-infected individuals

Immunocompromised individuals should generally not receive live attenuated vaccines.

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  1. Possible Side-Effects from Vaccines. Updated: December 2, 2016. Accessed: March 23, 2017.
  2. Information Sheet: Observed Rate of Vaccine Reactions: Measles, Mumps and Rubella Vaccines.
  3. Offit PA, Bell LM. Vaccines. John Wiley & Sons ; 2003
  4. Hviid A, Hansen JV, Frisch M, Melbye M. Measles, Mumps, Rubella Vaccination and Autism. Ann Intern Med. 2019; 170 (8): p.513. doi: 10.7326/m18-2101 . | Open in Read by QxMD
  5. Vaccines Do Not Cause Autism. Updated: November 23, 2015. Accessed: March 23, 2017.
  6. Vaccine Recommendations and Guidelines of the ACIP - Contraindications and Precautions. Updated: January 30, 2017. Accessed: February 13, 2017.
  7. Diphtheria, Tetanus, and Pertussis Vaccine Recommendations. Updated: December 17, 2018. Accessed: March 7, 2019.
  8. Rotavirus. Updated: November 15, 2016. Accessed: March 23, 2017.
  9. Epidemiology and Prevention of Vaccine-Preventable Diseases - Pertussis. Updated: September 29, 2015. Accessed: March 19, 2017.
  10. Opri R, Zanoni G, Caffarelli C, et al. True and false contraindications to vaccines. Allergol Immunopathol (Madr). 2018; 46 (1): p.99-104. doi: 10.1016/j.aller.2017.02.003 . | Open in Read by QxMD
  11. WHO - VACCINE SAFETY AND FALSE CONTRAINDICATIONS TO VACCINATION. Updated: January 1, 2017. Accessed: February 12, 2021.
  12. Lelie PN, Reesink HW, Grijm R, de Jong-Van Manen ST, Reerink-Brongers EE. Simultaneous passive and active immunization against hepatitis B: Noninterference of hepatitis B immune globulin with the anti-HBs response to reduced doses of heat-inactivated hepatitis B vaccine. Hepatology. 1986; 6 (5): p.971-975. doi: 10.1002/hep.1840060527 . | Open in Read by QxMD
  13. Leentvaar-Kuijpers A, Coutinho RA, Brulein V, Safary A. Simultaneous passive and active immunization against hepatitis A. Vaccine. 1992; 10 : p.S138-S141. doi: 10.1016/0264-410x(92)90569-6 . | Open in Read by QxMD
  14. Siber GR, Werner BG, Halsey NA, et al. Interference of immune globulin with measles and rubella immunization. J Pediatr. 1993; 122 (2): p.204-211. doi: 10.1016/s0022-3476(06)80114-9 . | Open in Read by QxMD
  15. Polio Elimination in the United States. Updated: October 25, 2019. Accessed: March 26, 2021.
  16. CDC - Haemophilus Influenzae Type b (Hib) VIS. Updated: October 29, 2019. Accessed: March 26, 2021.
  17. Vaccine Basics. Updated: March 23, 2017. Accessed: March 23, 2017.
  18. Songul Yalcin S, Engur Karasimav D, Yurdakok K. Measles vaccine failure in 9-month-old infants. Çocuk Enfeksiyon Dergisi/Journal of Pediatric Infection. 2016; 9 (4): p.153-160. doi: 10.5152/ced.2015.2195 . | Open in Read by QxMD
  19. Baicus A. History of polio vaccination. World J Virol. 2012; 1 (4): p.108. doi: 10.5501/wjv.v1.i4.108 . | Open in Read by QxMD
  20. Neonatal Immunology. Updated: January 1, 2018. Accessed: March 28, 2018.
  21. Foged C, Rades T, Perrie Y, Hook S. Subunit Vaccine Delivery. Springer ; 2014
  22. Epidemiology and Prevention of Vaccine-Preventable Diseases - Principles of Vaccination. Updated: November 15, 2016. Accessed: March 28, 2018.