Immunisation: aluminium adjuvant and injection route: practice question

A Pediatrics 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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Pediatrics · Immunisation: aluminium adjuvant and injection route

Sample item

A trainee wants to give pentavalent vaccine as a shallow subcutaneous injection in the infant's thigh fat because it looks easier. Why is deep intramuscular injection preferred for this vaccine?

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

The answer and the reasoning

A. The aluminium adjuvant can cause a sterile nodule or granuloma when deposited in fat

Adsorbed vaccines such as DPT, pentavalent, hepatitis B and Td contain aluminium salts. If these are deposited in subcutaneous tissue or the dermis they can cause local irritation, induration and sterile abscess, and antigen presentation is less effective. The anterolateral thigh is the preferred IM site in infants.

Option by option

  • A. The aluminium adjuvant can cause a sterile nodule or granuloma when deposited in fat (correct)

    Correct. Aluminium-adjuvanted vaccines cause local reactions and granulomas outside muscle.

  • B. The vaccine would be inactivated by fat enzymes before absorption

    There is no enzymatic inactivation of these antigens in fat; the concern is the adjuvant's local irritant effect.

  • C. The antigens are live and would multiply in subcutaneous fat

    Pentavalent vaccine is an inactivated and toxoid combination; it has no replicating organism.

  • D. Subcutaneous injection is painless and so gives a weaker immune response

    Pain is not the issue; the problem is local reaction and poorer immunogenicity from the adjuvant sitting in fat.

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.

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Questions about this Pediatrics question

What is the answer to this Pediatrics question?

The best answer is A, The aluminium adjuvant can cause a sterile nodule or granuloma when deposited in fat. Adsorbed vaccines such as DPT, pentavalent, hepatitis B and Td contain aluminium salts.

Why is "The vaccine would be inactivated by fat enzymes before absorption" not the answer?

There is no enzymatic inactivation of these antigens in fat; the concern is the adjuvant's local irritant effect.

Why is "The antigens are live and would multiply in subcutaneous fat" not the answer?

Pentavalent vaccine is an inactivated and toxoid combination; it has no replicating organism.

Why is "Subcutaneous injection is painless and so gives a weaker immune respo…" not the answer?

Pain is not the issue; the problem is local reaction and poorer immunogenicity from the adjuvant sitting in fat.

What concept does this question test?

It tests Immunisation: aluminium adjuvant and injection route in Pediatrics. If these are deposited in subcutaneous tissue or the dermis they can cause local irritation, induration and sterile abscess, and antigen presentation is less effective. The anterolateral thigh is the preferred IM site in infants.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Immunisation: aluminium adjuvant and injection route?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.