A 40-year-old executive who is a singaporean has been re-located by his firm to stay in the United States for a year. He sees his family doctor to find out about tetanus diphtheria (TD) and tetanus, diphtheria and acellular pertussis (TDap) immunisation for adults. Which of the following statements is CORRECT?

Correct Answer: C

Rationale: TDap is recommended once in adulthood to replace a TD booster, addressing pertussis resurgence.

Correct Answer: C

Rationale: Hepatitis B immunoglobulin provides passive immunity by supplying pre-formed antibodies, unlike vaccines (active immunity) or infection (natural active immunity). E is also correct, but the question implies a single answer, and C is explicitly passive.

Correct Answer: C

Rationale: Herd immunity protects unvaccinated individuals by reducing pathogen circulation; D and E are true, but C is the broadest correct single answer.

Correct Answer: C

Rationale: A 16mm needle is recommended for pre-term or small infants to ensure IM delivery, per Green Book.

Correct Answer: D

Rationale: A PSD is a written instruction from a prescriber to administer a medicine to a named patient, per Green Book.