Every year around flu season, there seems to be a flood of posts on social media from the anti-vaccine community telling everyone that they're going to get the flu or possibly turn into ninja turtle if they get the flu vaccine. This is dangerous misinformation. Firstly, we all know that the only way to become a ninja turtle is to be born a turtle, so don't get your hopes up. Secondly, vaccines save lives. Full stop. One of the major arguments made against vaccines is that they shed the virus. But what is vaccine shedding, really?
Somehow, anti-vaccine activists have managed to conflate virus shedding with vaccine shedding, without paying attention to the measurable differences between the two. Viral shedding, as per The Journal of Infectious Diseases, is the process by which a person sheds or passes on the virus via a cough or fluid contamination. It happens for a finite period of time, but it places people in their general vicinity at risk for contracting the infection. "Vaccine shedding" is the idea that those who are vaccinated are leaving bits of the virus wherever they go as a side effect of the vaccine. While there are documented cases of this phenomenon, it's only in live virus vaccines, noted Vaccine, and even then, the risk they pose is extremely minimal in most cases.
This is because getting a live virus or live attenuated vaccine is not the same as getting the virus, and therefore it is far less contagious. That doesn't mean that pediatricians should forget about the risks entirely, and they don't. They're always researching the ways vaccines interact with the community and how vaccines could affect those most vulnerable, like those who are immunodeficient or other populations like premature babies. In fact, a recent study in Pediatrics looked at babies in the NICU. All very ill or young, some were vaccinated with the live attenuated rotavirus vaccine and others were not. None of the unvaccinated babies contracted the virus, determining the risk at nearly nil. These are some of the most at-risk children around, and none of them got it.
As per the Centers for Disease Control and Prevention (CDC), "Although live attenuated vaccines replicate, they usually do not cause disease such as may occur with the 'wild' form of the organism. When a live attenuated vaccine does cause 'disease,' it is usually much milder than the natural disease and is referred to as an adverse reaction." And they're highly unlikely to transmit it to anyone else, certainly not to anyone healthy.
The majority of vaccines that are given aren't live — they're what's referred to as "inactivated vaccines," such as the flu shot. They don't shed and they don't give you that virus. You don't get the flu from the flu shot. If you feel crappy after the administration of the flu jab, it's not because it gave you the flu, it's because it triggered an immune response. Good news! Your immune system is working, and now that you're vaccinated, you're far less likely to give a potentially deadly virus to someone who can't get the vaccine, like children with leukemia or HIV.
According to the CDC, the list of live attenuated virus vaccines is quite short, and limited to "measles, mumps, rubella, vaccinia, varicella, zoster (which contains the same virus as varicella vaccine but in much higher amount), yellow fever, and rotavirus." It should be noted that the first three are in a combined vaccine, limiting the risk even further.
However, there is one distinct vaccine that does shed and can be a concern, and probably the impetus for the fury over what is vaccine shedding, but very few Americans will ever need to worry about getting it — smallpox. It's a tricky vaccine that requires some care, according to the CDC. But unless you're traveling to a region where you're likely to encounter it, or you're a first responder, you're not going to get the vaccine. But, it should be noted, that taking a little care and getting the shot is way better than getting smallpox.
Vaccine shedding simply isn't something to concern most parents — at least not more than the very real dangers of measles or rotavirus.
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