Saar Kuzi
Alessandra Coutinho Fernandes
William Cope
Richard Tapping
Kashif Ahmad
Reda Sadki
Shubhra Kanti Karmaker Santu
Adam P Rusch
Elle Meisner
Nereyda Ochoa
Landon J. Kunzelman
James DotimasFA16 Immunization Module’s Updates
Live versus Inactivated Vaccines
Live Attenuated Vaccines
Live vaccines are derived from modifying “wild,” or disease-causing, viruses or bacteria in a laboratory. These are weakened by repeated culturing. For instance, the measles vaccine today was derived from the measles virus in a child with measles disease in 1954. Therefore, it took about 10 years of repeated culturing to transform the disease-causing measles virus to an attenuated live vaccine.
Live vaccines usually only require one small dose to produce immunity. This immune response is identical to responses to natural infection.
Some problems with live attenuated vaccinations:
- Live attenuated vaccines may cause fatal reactions due to uncontrolled replication.
- It usually does not cause illness in normal patients, but when it does, it is a much milder version of the natural disease. This is called an adverse reaction.
- A live attenuated vaccine virus could theoretically revert to its original pathogenic (disease-causing) form and cause disease especially in immunodeficient patients.
- Active immunity from a live attenuated vaccine may not develop due to interference from circulating antibody to the vaccine virus.
- Live attenuated vaccines are fragile and can be easily destroyed by heat and light, which is why they require careful handling.
Currently available live attenuated viral vaccines are measles, mumps, rubella, vaccinia, varicella, etc.
Inactivated Vaccines
Inactivated vaccines are produced by growing the bacterium or virus in culture media, then inactivating it with heat or chemicals like formalin. These are not alive so they cannot replicate. Unlike live vaccines, inactivated ones cannot cause disease from infection, even in an immunodeficient person. Inactivated antigens, also unlike live vaccines, are less affected by circulating antibody.
Inactivated vaccines always require multiple doses because antibody titers against inactivated antigens diminish with time. As a result, “booster” shots are needed to boost the immune response.
Some examples of inactivated vaccines include (hepatitis B, influenza, acellular pertussis, human papillomavirus, anthrax) and toxoids (diphtheria, tetanus.)
QUICK COMPARISON
| Live Attenuated Vaccine | Inactivated Vaccine |
| Requires only one dose to produce immunity | Requires 3-5 doses |
| Must replicate to be effective-poses risk of uncontrolled growth/replication | Cannot replicate so no risk of uncontrolled growth |
| Immune response most similar to natural infection | Most of immune response is humoral |
| Response might not develop due to interference from circulating antibody | Usually not affected by circulating antibody |
| May cause disease in immunodeficient patients | Will not cause disease even in immunodeficient patients |
References:
Resource 4: Principles of Vaccination Document from the CDC
The table is so helpful in comparing the two types of vaccines. You mentioned that boosters are required because the antibody titer for a specific antigen diminishes. I wonder why immunity decreases as time progresses, especially with active immunity.
@MadelineBell I'm wondering the same thing! Somebody else made a post about different groups (A, B, and C, I think) that weren't supposed to get certain vaccines, and diabetics were in the third group.
I got so sick when I got the typhoid live attenuated virus. It was awful. But then I didn't get typhoid in Central America, so I'm going to call that a win. Do you know if the CDC/WHO considers diabetics to be immunocompromised?
Very interesting. I wonder what the threshold is for a bacteria to be considered attenuated enough to be used as a live vaccine.