Vaccines What You Need to Know About Live Virus Vaccines By Pat Bass, MD twitter linkedin Dr. Bass is a board-certified internist, pediatrician, and a Fellow of the American Academy of Pediatrics and the American College of Physicians. Learn about our editorial process Pat Bass, MD Medically reviewed by Medically reviewed by Sanja Jelic, MD on November 04, 2019 Sanja Jelic, MD is board-certified in pulmonary disease, sleep medicine, critical care medicine, and internal medicine. She is an assistant professor and attending physician at Columbia University College of Physicians and Surgeons in New York, NY. Learn about our Medical Review Board Sanja Jelic, MD Updated on January 27, 2020 Print Table of Contents View All Common Live Virus Vaccines Risks Other Vaccine Differences Vaccine Benefits A live virus vaccine contains a weakened, live virus that is designed to help your body develop an immune response without you developing symptoms of the disease it is intended to prevent. The virus is teaching your immune system what the virus looks like and allows the body to develop an immune response. Many vaccines of this type allow for life-long immunity to develop with only one or two doses needed. TEK IMAGE / SCIENCE PHOTO LIBRARY / Getty Images Because these vaccines contain a small amount of a weakened live virus, they should not be given to patients with weakened immune systems, such as patients on high-dose steroids, undergoing cancer chemotherapy treatment, or if they have certain diseases such as HIV. Pregnant women should not receive live virus vaccines. While most inactivated viruses require multiple doses, live virus vaccines often require only one or at least fewer doses (e.g. shingles vaccine, or the measles, mumps and rubella vaccine) and can develop an immune response equal to contracting the live virus. One downside of these vaccines is that they require refrigeration, which can limit the ability to use these vaccinations in some areas. If these vaccines are not kept at the correct temperature, they can become inactive and the immunization may not be effective. Also, some live virus vaccines come as a powder and require mixing with a particular fluid before being administered. Mixing with the wrong kind of fluid or an incorrect amount of fluid are potential errors that may lead to poor vaccine performance. Newer technology allows live virus vaccines to be introduced as a vector or "trojan horse." In this type of vaccine, the live virus introduces a piece of DNA into the body. The DNA is what causes the immune response, not the virus. The virus enables exposure and allows the DNA to bypass your body's immune system detection initially. In this scenario, the live virus is the trojan horse carrying the DNA into the body. Practice Talking to Someone Skeptical About Vaccines Using Our Virtual Conversation Coach Common Live Virus Vaccines Intranasal FluMeasles, Mumps and Rubella VaccineRotavirus VaccineVaricella Virus Vaccine Risks While small, there is always the risk that the weakened virus could change and end up causing disease rather than preventing it. How Are Other Vaccines Different If you are a parent, then you know there are many different kinds of vaccines your pediatrician asks you to give your child. Some of the other types of vaccines are outlined below. Killed (inactivated) vaccines are made from a protein or other part of a virus or bacteria. The flu shot is an example of a killed vaccine. Inactivated vaccines are easier for your health care provider to handle. Most do not require refrigeration, special mixing or shipping requirements. The longer shelf life means they are more likely to be offered in your physician's office. With inactivated vaccines, you are not at risk of developing the disease that the vaccine is intended to prevent. One of the common flu myths and reason people refuse the flu vaccine is that they get the flu with vaccination. Inactivated vaccines (e.g. polio and pertussis) often require multiple doses during initial immunization and periodic booster doses for continued protection. This sometimes contributes to decreased immunization rates. Toxoid vaccines do not produce immunity to the actual infection. Rather, the vaccine contains a toxin or chemical made by the bacteria or virus that prevents the harmful effects of the infection. Exposure teaches your body's immune system how to fight off the toxin without you developing the side effects of full exposure. Subunit vaccines contain certain parts of a bacteria or virus that will stimulate an immune response but will not lead to the development of the disease. Conjugate vaccines do not specifically target the actual virus or bacteria, but the outer shells the bacteria or virus use to try to mask themselves from your immune system. This type of vaccination works particularly well in young, less mature immune systems. Biosynthetic vaccines are just like the name implies. A scientist creates a manmade substance that is similar enough to the virus or bacteria that the body creates an immunogenic response. The Hib (Haemophilus influenzae type B) conjugate vaccine is an example. Vaccine Benefits Vaccines are one of the true public health success stories. Tetanus, diphtheria, mumps, measles, whooping cough, meningitis, and polio are examples of a number of diseases that used to be common. Not only do these diseases cause significant illness, but they can also cause lifelong medical problems and even death. While not all of these diseases have been eradicated as polio has, vaccines have significantly reduced the incidence and complications from these diseases. Vaccines Doctor Discussion Guide Get our printable guide for your next doctor's appointment to help you ask the right questions. Download PDF Email the Guide Send to yourself or a loved one. Sign Up This Doctor Discussion Guide has been sent to {{form.email}}. There was an error. Please try again. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health 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. About the vaccine. Updated March 28, 2019. Centers for Disease Control and Prevention. Contraindications and precautions. Updated November 15, 2019. Centers for Disease Control and Prevention. Vaccine storage and handling. Updated April 15, 2019. Liu MA. A comparison of plasmid DNA and mRNA as vaccine technologies. Vaccines (Basel). 2019;7(2). doi:10.3390/vaccines7020037 Centers for Disease Control and Prevention. Live, intranasal influenza VIS. Updated August 15, 2019. Centers for Disease Control and Prevention. Rotavirus vaccination. Updated July 25, 2018. MedlinePlus. Vaccines (immunizations) - overview. Updated January 6, 2020. Centers for Disease Control and Prevention. Misconceptions about seasonal flu and flu vaccines. Updated September 25, 2019. Centers for Disease Control and Prevention. Polio vaccination. Updated May 4, 2018. World Health Organization. Toxoid vaccines. National Institute of Allergy and Infectious Diseases. Vaccine types. Updated July 1, 2019. Centers for Disease Control and Prevention. Understanding how vaccines work. Updated July 2018. Centers for Disease Control and Prevention. Hib (Haemophilus influenzae type b) vaccination. Updated February 13, 2018. Additional Reading CDC. Basic and Common Questions. World Health Organization. Live attenuated vaccines (LAV).