Health Conditions A-Z Infectious Diseases COVID-19 Does Vaccine Shedding Really Happen? None of the COVID-19 vaccines approved in the United States cause vaccine shedding. By Joni Sweet Joni Sweet Joni Sweet is a freelance writer and editor who specializes in travel, health, and wellness. Her work has been published by Health, SELF, Healthline, National Geographic, Forbes, Lonely Planet, Thrillist, and dozens of other publications. When she’s not traveling the world, she can be found practicing yoga, riding her bike, and looking for the best vegetarian food in the Hudson Valley. health's editorial guidelines Updated on January 15, 2024 Medically reviewed by Rochelle Collins, DO Medically reviewed by Rochelle Collins, DO Rochelle Collins, DO, is a board-certified family medicine physician and assistant clinical professor of family medicine at Quinnipiac University. learn more Trending Videos Close this video player FatCamera / Getty Images You may have heard people voice their concerns about vaccine shedding. Vaccine shedding, or viral shedding, happens when a vaccine releases parts of a virus, resulting in the spread of an infection. Though vaccine shedding can occur, the potential for the occurrence only happens with live-attenuated vaccines. Here's what to know about different vaccines, including which specific ones may lead to vaccine shedding. What Is Vaccine Shedding? Vaccine shedding is a process of the body releasing viral particles from a vaccine and hypothetically creating a risk of infection to others. However, vaccine shedding can only happen with certain types of vaccines—ones that are live-attenuated vaccines. Types of Vaccines There are various types of vaccines available to protect individuals. They work in different ways to offer protection. Conjugate, Polysaccharide, Recombinant, and Subunit Vaccines that fall under this category use pieces of germs to achieve a targeted immune response. Almost every person—even people—may be able to get these types of vaccines. However, they may require booster shots for continuous disease protection. Inactivated A dead version of a germ responsible for an illness or condition helps make up an inactivated vaccine. Booster shots are also necessary with these vaccines, as their level of immunity is weaker than that of live vaccines. Live-Attenuated Live-attenuated vaccines use a weaker version of a germ to help protect you against illnesses. Their immunity strength is higher and lasts longer. In fact, you can end up with lifetime protection with two or fewer live-attenuated vaccine doses. Messenger RNA With messenger RNA (mRNA) vaccines, the vaccines trigger the body to produce a protein that causes an immune response in our bodies. Antibody production is part of this immune response. These antibodies protect you if you are exposed to the germ or virus. Toxoid These types of vaccines include a germ-created toxin, which is a harmful product, to create immunity against the part of the germ that leads to the disease. You may need boosters for toxoid vaccines. Viral Vector Viral vector vaccines offer protection by including a virus modification. The version of the virus in the vaccine is harmless and helps cells recognize and protect you from germs. Does the COVID-19 Vaccine Cause Shedding? The short answer is no; none of the COVID vaccines cause shedding. Even though vaccine virus shedding is a potential (yet extremely rare) risk with live attenuated vaccines, it doesn't apply to these vaccines since they don't contain the live virus that causes COVID. The Pfizer-BioNTech and Moderna vaccines are mRNA COVID vaccines, while the Novavax vaccine is a protein subunit COVID vaccine. Which Vaccines Shed? The only way vaccine shedding occurs is from a live attenuated vaccine, which works by letting the virus replicate inside a person's body enough to stimulate an immune response but not enough to cause the disease itself. Live-attenuated vaccines used in the US include ones for the following conditions: Chickenpox: The vaccine for chickenpox is given in two doses and is 90% effective. Measles, mumps, and rubella (MMR): There is a 97% effectiveness rate against measles, a 93% rate against rubella, and a 78% rate against mumps with two doses of this vaccine. Influenza (flu): The vaccine for the flu, in nasal spray form, is approved for most individuals aged 2 to 49—except for people with certain medical conditions and people who are pregnant or immunocompromised. Rotavirus: A baby may receive a rotavirus vaccine in two or three doses, depending on which one is used. The child must have all doses of either vaccine by the time they reach 8 months of age. Typhoid fever: Typhoid vaccines don't have a 100% effectiveness rate; you'll need boosters with this vaccine. If you receive the oral vaccine, you need a booster every five years, but if you receive the injectable vaccine, you need a booster every two years. Viral shedding rarely leads to disease in others. Overall, live attenuated vaccines are generally safe and pose minimal risk. The main exceptions are in individuals who are immunocompromised and those who are pregnant. A Quick Review Many vaccine types exist, but live attenuated vaccines are the only ones with the potential to result in vaccine shedding. In particular, none of the vaccines used against the COVID virus utilize attenuated live vaccine technology so vaccine shedding won't happen with them. However, don't hesitate to contact a healthcare provider if you have concerns about vaccines or vaccine shedding. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit 11 Sources Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Centers for Disease Control and Prevention. Bust myths and learn the facts about COVID-19 vaccines. U.S. Department of Health and Human Services. Vaccine types. Centers for Disease Control and Prevention. Understanding how COVID-19 vaccines work. Centers for Disease Control and Prevention. Overview of COVID-19 vaccines. Centers for Disease Control and Prevention. Principles of vaccination. Centers for Disease Control and Prevention. Chickenpox/varicella vaccination. Centers for Disease Control and Prevention. Measles, mumps, and rubella (MMR) vaccination: what everyone should know. Centers for Disease Control and Prevention. Key facts about seasonal flu vaccine. Centers for Disease Control and Prevention. Rotavirus vaccination: what everyone should know. Centers for Disease Control and Prevention. Typhoid fever and paratyphoid fever - vaccination. MedlinePlus. Vaccines - immunizations.