What is vaccine shedding? by Dr. Joseph Mercola for Mercola
When you’re infected with a virus that causes an illness, that virus is shed in your saliva and other bodily fluids, and sometimes also via skin lesions. This means that a person who comes into direct contact with the shed virus may also become infected. The same holds true for live attenuated viral vaccines.
While inactivated vaccines use a killed version of the pathogen, live viral vaccines use a weakened (or attenuated) version of the virus. Typically, the live virus used in vaccine production is passed through a living cell culture or other host, such as chicken embryo, many times over until it becomes weakened to a point that it’s not likely to make you sick when it’s injected or, in the case of live oral vaccines, swallowed.
That being said, a live vaccine strain virus is still active and strong enough to trigger an inflammatory response in your body, prompting the creation of vaccine-acquired antibodies. There are a few problems with this, such as the possibility that the weakened vaccine-strain virus can revert to virulence, leading to serious complications identical or similar to complications of the natural disease the vaccine is supposed to prevent in the vaccinated person.1
Another noted problem is that the person who is given a live attenuated viral vaccine can asymptomatically shed and transmit vaccine-strain virus for a period of days, weeks or months and potentially infect close contacts, who can also experience symptoms of the very disease the vaccine was intended to prevent.
Live flu vaccine associated with increased viral shedding in exhaled breath
The possibility of vaccine strain viral shedding takes on renewed importance in the case of the government’s strong recommendation for annual flu vaccination. The U.S. Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccinations for everyone 6 months and older.
In the 2018 to 2019 flu season, CDC officials recommended health care providers “use any licensed, age-appropriate influenza vaccine (inactivated influenza vaccines (IIV), recombinant influenza vaccine (RIV), or live attenuated influenza vaccine (LAIV4) with no preference expressed for one vaccine over another.”2
The live influenza vaccine FluMist, which is approved for nonpregnant women as well as anyone aged 2 to 49 years, is administered in the form of a nasal spray.
While the CDC states that the live type A and B vaccine strain influenza viruses in FluMist are too weak to actually give recipients influenza, research has raised some serious doubts that this is the case. One recent study revealed not only that influenza virus may be spread via simple breathing (i.e., no sneezing or coughing required) but also that repeated vaccination increases the amount of influenza virus released into the air.3
“Self-reported vaccination for the current season was associated with a trend toward higher viral shedding in fine-aerosol samples; vaccination with both the current and previous year’s seasonal vaccines, however, was significantly associated with greater fine-aerosol shedding … ,” the researchers stated.4
What’s more, individuals who had been vaccinated in the current and previous season had 6.3 times more aerosol shedding than those who had received no vaccination in those two seasons. The researchers concluded:5
“The association of current and prior year vaccination with increased shedding of influenza A might lead one to speculate that certain types of prior immunity promote lung inflammation, airway closure and aerosol generation … If confirmed, this observation, together with recent literature suggesting reduced protection with annual vaccination, would have implications for influenza vaccination recommendations and policies.”