Immunology: live vaccines in immunodeficiency: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Immunology: live vaccines in immunodeficiency

Sample item

A 3-month-old with severe recurrent infections and absent T cells develops disseminated infection with regional lymphadenitis a few weeks after a birth dose. Which vaccine is the likely cause?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. BCG

Live attenuated BCG can disseminate in children with severe T cell defects such as SCID, so live vaccines are contraindicated in this setting. Hepatitis B, toxoid and inactivated polio vaccines contain no replicating organisms.

Option by option

  • A. Diphtheria toxoid

    Diphtheria toxoid is an inactivated toxin.

  • B. Inactivated polio vaccine

    Inactivated polio vaccine contains killed virus and cannot replicate.

  • C. Hepatitis B vaccine

    Hepatitis B vaccine is a recombinant subunit vaccine.

  • D. BCG (correct)

    Correct. Live BCG can cause disseminated disease in SCID.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Microbiology questions

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is D, BCG. Live attenuated BCG can disseminate in children with severe T cell defects such as SCID, so live vaccines are contraindicated in this setting.

Why is "Diphtheria toxoid" not the answer?

Diphtheria toxoid is an inactivated toxin.

Why is "Inactivated polio vaccine" not the answer?

Inactivated polio vaccine contains killed virus and cannot replicate.

Why is "Hepatitis B vaccine" not the answer?

Hepatitis B vaccine is a recombinant subunit vaccine.

What concept does this question test?

It tests Immunology: live vaccines in immunodeficiency in Microbiology. Hepatitis B, toxoid and inactivated polio vaccines contain no replicating organisms.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Immunology: live vaccines in immunodeficiency?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.