December 2009 LSAT Section 1 Question 11

Many vaccines create immunity to viral diseases by introducing a certain portion of the disease–causing virus's outer...

Derek on August 26, 2014

Why A?

If the conclusion is that the doctors claim they can produce a vaccine that will produce permanent immunity to that disease then how does A ( most young people who contract hepatitis E are young adults who were probably exposed to the virus in childhood) counter the argument? If they have a cure, then giving it to infants would produce permanent immunity from that disease in the future. They never claim it can wipe out everything currently existing, so it seems answer A is irrelevant.

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Naz on September 3, 2014

The doctors' claim is that they can produce a vaccine that will produce permanent immunity to hepatitis E.

Why? Because many vaccines create immunity to viral diseases by introducing a certain portion of the disease-causing virus's outer coating into a patient's body. The exposure of this portion of the virus is just as effective as "exposure to the whole virus" in stimulating production of antibodies that will recognize and subsequently kill the whole virus. Doctors have found a suitable portion of the virus that causes hepatitis E.

Answer choice (A) states: "Most of the people who contract hepatitis E are young adults who were probably exposed to the virus in childhood also."

If most of those who contract hepatitis E are young adults who were probably exposed to the virus in childhood, then their bodies should have been triggered the initial time they were exposed to create antibodies that should have recognized and killed the virus when they were young adults--"Exposure to that part of a virus (the part found in a vaccine) is as effective as exposure to the whole virus in stimulating production of antibodies that will subsequently recognize and kill the whole virus."

However, even though these people had been exposed to the whole virus when they were children, their bodies did not ward off the virus later in their lives--they still contracted the disease when they were young adults.

Thus, it is unlikely that isolating the suitable portion of the virus, which would stimulate antibody production, will create a vaccine that will produce permanent immunity to that disease--since all the vaccine will do is create antibodies in the people it is administered to and most people who get hepatitis E have already been exposed to the virus in childhood i.e. they already have antibodies that should have warded off the disease.

This is why answer choice (A) counters the doctors' claim--it eliminates the possibility that the production of antibodies will adequately ward off the effects of being exposed to the whole virus.

Hope that was helpful! Please let us know if you have any other questions.

Margarita on October 24 at 11:13PM

extremely helpful explanation. Thank you