Vaccine shedding

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Vaccine shedding is a term used for the rare release of virus following administration of a live-virus vaccine. Shedding is a popular anti-vaccination trope,[1][2][3] but, with the exception of the oral polio vaccine (OPV) in the 1950s, there have only been a few documented cases of vaccine-strain virus infecting contacts of a vaccinated person.[4]

Viral shedding is part of the mechanism of virus transmission.[5] Shedding is impossible with killed vaccines or those made using only isolated proteins (most vaccines fall into one of these two classes), but a small number of vaccines contain live attenuated virus which can theoretically infect others. Not all pathogens are shed, shedding does not equal transmission, and transmission does not always cause disease.[6]

The only vaccine to have caused any significant number of infections is the oral polio vaccine (OPV) in the 1950s,[7] and this vaccine is no longer used. The route of infection was through contact with faeces, and some vaccines, like the viruses they prevent, are shed in stool for up to 28 days.[8] Normal hygiene is sufficient to prevent infection[9] but immunocompromised individuals need to be especially diligent.[10] Other attenuated vaccines show no significant shedding, inadvertent infection is rare[11] (for example, there are 11 cases of chickenpox which may have been transmitted by vaccinated individuals out of approximately 50 million doses),[12] and only a single case of transmission of influenza virus has been documented, and that person remained asymptomatic.[13] The attenuated virus from vaccines is much weaker and less likely to infect than the wild virus.[14]


  1. ^ Vaccine Rejection and Hesitancy: A Review and Call to Action, Open Forum Infect Dis. 2017 Summer; 4(3): Jul 18 2017. doi:10.1093/ofid/ofx146
  2. ^ Anti-vaccine activists, Web 2.0, and the postmodern paradigm – an overview of tactics and tropes used online by the anti-vaccination movement. Vaccine. 2012 May 28;30(25):3778–89. doi:10.1016/j.vaccine.2011.11.112. Epub 2011 Dec 13.
  3. ^ Tracking anti-vaccination sentiment in Eastern European social media networks, UNICEF
  4. ^ "Can vaccines cause or spread diseases?". Northern Rivers Vaccination Supporters. Retrieved 2018-04-29.
  5. ^ Hall, C. B; Douglas Jr, R. G; Geiman, J. M; Meagher, M. P (1979). "Viral shedding patterns of children with influenza B infection". The Journal of Infectious Diseases. 140 (4): 610–13. doi:10.1093/infdis/140.4.610. PMID 512419.
  6. ^ "Can vaccines cause or spread diseases?". Northern Rivers Vaccination Supporters. Retrieved 2018-04-29.
  7. ^ "Vaccines: Breaking down and debunking 10 myths". USA Today. Retrieved 2018-04-29.
  8. ^ "Who Should not Get Vaccinated". 2018-03-28. Retrieved 2018-04-29.
  9. ^ "Ask the Experts about Rotavirus Vaccines – CDC experts answer Q&As". Retrieved 2018-04-29.
  10. ^ Anderson, Evan J (October 2008). "Rotavirus vaccines: viral shedding and risk of transmission". The Lancet Infectious Diseases. 8 (10): 642–49. doi:10.1016/s1473-3099(08)70231-7. ISSN 1473-3099. PMID 18922486.
  11. ^ King, James C.; Treanor, John; Fast, Patricia E.; Wolff, Mark; Yan, Lihan; Iacuzio, Dominic; Readmond, Bernard; O'Brien, Diane; Mallon, Kenneth (2000-02-01). "Comparison of the Safety, Vaccine Virus Shedding, and Immunogenicity of Influenza Virus Vaccine, Trivalent, Types A and B, Live Cold-Adapted, Administered to Human Immunodeficiency Virus (HIV)-Infected and Non-HIV-Infected Adults". The Journal of Infectious Diseases. 181 (2): 725–28. doi:10.1086/315246. ISSN 0022-1899. PMID 10669363.
  12. ^ "vaccine-shedding - The Immunization Partnership". Retrieved 2018-04-29.
  13. ^ Tosh, Pritish K.; Boyce, Thomas G.; Poland, Gregory A. (January 2008). "Flu myths: dispelling the myths associated with live attenuated influenza vaccine". Mayo Clinic Proceedings. 83 (1): 77–84. doi:10.4065/83.1.77. ISSN 0025-6196. PMID 18174020.
  14. ^ "Childhood flu programme: information for healthcare practitioners". GOV.UK. Retrieved 2018-04-29.