I started a thread recently about whether viruses are alive or not. It looks like that thread may be been wiped out in the recent Board changes. But the preponderance of information from the Teeming Millions (or dozens in this case) was that a virus is not truly alive.
So how come they say that vaccines are not made with “live” virus so it won’t make you sick?
http://www.mrs.umn.edu/~goochv/CellBio/lectures/virus/virus.html
Looks like it’s up for debate as to whether they are alive or not.
Great quote, succintly summarizes both sides.
So what do they mean when they say that a vaccine is made of “dead” virus?
A “dead” virus doesn’t necessarily imply that it was once alive.
For example I have a dead battery on my desk.
A dead virus is one that is inactive, just like my stupid battery. Neither was ever alive.
It’s been inactivated by removing a protein or nucleic acid sequence. The virus is no longer functional and can not cause an infection, only an immune response.
Not much different than other usage of “dead” such as “The engine died”
On preview, I see Slip has beat me to it, but I’ll post anyway.
Au contraire! I understand what deactivates a battery (all its oomph has been used up) but Slip did not describe how a virus gets deactivated, which you did. Thanks.
An example of a “dead” vaccine is the Salk polio vaccine. This uses a “dead” (inactivated) polio virus. When injected into your arm, the dead virus stimulates an immune reaction that results in immunity to infection with the “wild” virus.
An example of a live virus vaccine is the Sabin polio vaccine. The Sabin vaccine uses an attenuated (weakened) poliovirus that is “live” in the sense that after you swallow it and it reaches your intestines it sets up shop and reproduces. Unlike “wild” polio virus, it does not cause disease (or almost never causes disease) because it is attenuated. The Sabin vaccine was a big advance on the Salk vaccine because it is easier to give (oral, rather than injectable) and because, being “alive” it reproduces itself in the intestines of immunized people, thus spreading itself around, just like “wild” poliovirus, resulting in immunity among people who haven’t even been immunized themselves but who were simply exposed to the vaccine virus through contaminated food or drink or whatever. However, although this advantage of a “live” vaccine helped greatly to elimininate polio and and saved thousands of lives, it had the disadvantage of causing polio in a tiny fraction of people exposed to the virus. This was not a problem initially because everyone (or, at least, rational people) will agree that a tiny risk of getting vaccine-associated polio is better than a vastly larger risk of getting wild type polio. However, once polio was nearly eradicated in the U.S., the number of cases of vaccine-associated polio got to be higher than the number of cases of wild type polio so the switch was made to the (inactivated) Salk vaccine.
Since there is still a scientific debate as to whether a virus is “alive”, the term “dead” becomes semantics. Back in my lab days studying drinking water disinfection, we used the term “inactivating” for a virus whereas we’d “kill” bacteria. But then again, we were engineers, not microbiologists.
There are two kinds of vaccines; live attenuated and inactivated.
For the first type, the wild virus or bacteria is modified in the laboratry in some way that still lets it grow (or reproduce) in the body to trigger immunity, but won’t usually cause disease. “Attenuated” means weakened. Many of these vaccines must be treated carefully, avoiding heat and/or light or they can be rendered ineffective. The only “live” vaccine that has reverted back to it’s original form to cause actual disease was live polio vaccine. This is why oral polio vaccine should not be given to people with immune deficiency diseases (or their close contacts). There have been no serious adverse events reported from the currently available injectable polio vaccine.
The second type, inactivated, are produced by inactivating the organism with heat or chemicals. Sometimes only a part of the bacteria or virus are needed for the vaccine. They generally require multiple doses to be effective.
The best immune response is produced by a vaccine that is most similar to the natural disease.