'Vaccines are often administered before a diagnosis of combined immune deficiency is made. …live vaccines may produce chronic infections in patients with combined immune deficiency.” – Infectious Diseases Society of America (2013)
“It is now known that vaccine viruses can be serially transmitted through human hosts, and may revert genetically toward wild-type transmissibility and virulence.” — U.S. and European health officials (2008)
Vaccine Strain Live Viruses Can Infect Others
Just like people with viral infections can shed and transmit wild-type virus, 86 people given live virus vaccines can shed and transmit vaccine strain live attenuated virus. 87 Like wild-type virus, vaccine strain live virus can be shed in body fluids, such as saliva, 88 89 nasal and throat secretions, 90 breastmilk, 91 92 urine and blood, 93 94 stool, 95 and skin lesions. 96 Shedding after vaccination with live virus vaccines may continue for days, weeks or months, depending upon the vaccine and the health or other individual host factors of the vaccinated person.
Vaccinia Virus Shedding for Two to Three Weeks
After primary smallpox vaccination, vaccinia virus is shed for two to three weeks and can be transmitted to others through body secretions and especially through skin contact with the open vaccinia virus lesions at the site of the vaccination until the lesion scabs over and separates from the skin. The CDC states:
“After a person is vaccinated with vaccinia, the vaccination site contains infectious virus from the time of papule formation until the scab separates from the skin (a period of approximately 2–3 weeks). During this period, a risk exists for inadvertent inoculation to another body site or another person. The most frequently reported sites of vaccinia infections caused by unintentional transfer are the face, nose, mouth, lips, genitalia, anus, and eye.”
In 1961, the Sabin live attenuated oral polio vaccine (OPV) was licensed and soon U.S. public health officials recommended that all infants and children be given OPV instead of the inactivated, injectable Salk vaccine, which had been licensed in 1955 and widely used. OPV contains three vaccine strain polioviruses given orally by liquid drops in the mouth and public health officials adopted the Sabin live attenuated oral polio vaccine (OPV) as the preferred polio vaccine because OPV not only vaccinated the recipient but also “passively” vaccinated those coming in close contact with a recently vaccinated child shedding vaccine strain live polioviruses in the stool, saliva and nasal secretions.”'
Read more: Why Children that Have Been Recently Vaccinated with Live Virus Vaccines Should be the Ones that Are Isolated (Rather than the Healthy Unvaccinated Ones)