In most cases, having an immunodeficiency should not prevent a person from getting a vaccine. As stated earlier in the course, most vaccines consist of killed organisms or components of organisms. As such, they can not cause disease even in someone with an immunodeficiency. Live attenuated vaccines, however, can possibly represent a threat. Examples of live attenuated vaccines include yellow fever, varicella, BCG (for TB), and measles. That being said, it does not mean that the vaccine will be as effective in someone with immunodeficiency as it would be in a healthy person; in fact, depending on how severe the deficiency is, it might not create immunity at all.
Serious side effects in most individuals are rare. Anaphylactic reactions are the most common of these rare side effects but occur in only about one in a million doses. People with known allergies to certain substances that can be in the vaccine like egg proteins should avoid those particular vaccines.
Many people are convinced that there is a connection between vaccines containing thimerosal and autism. Although thimerosal has been voluntarily withdrawn from most vaccines as a precaution, there is no scientific evidence of any link between it and autism.
Generally, most people experience only mild local side effects such as pain at the injection site, slight fever, or malaise. In other words, the risk of getting the disease is far worse than any possible short-term side effects.
