Vaccine shedding

Vaccine shedding is a term used for the 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 been few documented cases of vaccine-strain virus infecting contacts of a vaccinated person.[4]

Viral shedding is part of the normal 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]

Regulatory authorities in the USA and EU recommend that shedding data should be collected both during the development phase of a new product and during clinical trials. A full report on shedding must subsequently be included in the Biologics license application.[15][16]

A study of 345 participants aged 5–49 years who received the live influenza virus vaccine LAIV3, and for whom shedding was assessed by viral culture of nasal swabs (daily for days 1–7 post vaccination, every other day for days 9 through 25, and on day 28) indicated that 30% had detectable virus in nasal secretions obtained by nasal swabbing. In an open-label study of 200 children aged 6–59 months who received a single dose of LAIV3, shedding of low titers of at least one vaccine virus was detected on culture in 79% of children and was more common among the younger recipients. Serious illnesses have not been reported among unvaccinated persons infected inadvertently with vaccine viruses. The estimated probability of transmission of vaccine virus within a contact group with a single LAIV recipient in this population was 0.58%. [17]

References
  1. Vaccine Rejection and Hesitancy: A Review and Call to Action,. Open Forum Infect Dis. 2017 Summer; 4(3): (Report). 18 July 2017. doi:10.1093/ofid/ofx146.CS1 maint: extra punctuation (link)
  2. Anti-vaccine activists, Web 2.0, and the postmodern paradigm – an overview of tactics and tropes used online by the anti-vaccination movement. Epub 2011 Dec 13. "Vaccine", 2012 May 28;30(25):3778–89. (Report). 13 December 2011. doi:10.1016/j.vaccine.2011.11.112.
  3. "Tracking anti-vaccination sentiment in Eastern European social media networks]" (PDF). 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". www.cdc.gov. 2018-03-28. Retrieved 2018-04-29.
  9. "Ask the Experts about Rotavirus Vaccines – CDC experts answer Q&As". www.immunize.org. 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". www.immunizeusa.org. 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.
  15. "Design and Analysis of Shedding Studies for Virus or Bacteria-Based Gene Therapy and Oncolytic Products; Guidance for Industry | FDA". www.fda.gov. Retrieved 2021-01-11.
  16. Longhurst, Sharon. "CURRENT REGULATORY THINKING FOR VIRAL SHEDDING STUDIES IN THE EUROPEAN UNION" (PDF). European Medicines Agency. Retrieved 11 January 2021.
  17. "Safety of Influenza Vaccines- Safety of Inactivated Influenza Vaccines (IIVs)". www.cdc.gov. 24 August 2017. Retrieved 3 February 2021.
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