[3] Heffernan's research involved the development of cold chain standards, which are important for the safe management and storage of vaccines.

[3] She also carried out surveillance for infectious diseases, allowing the rate of spread of antimicrobial resistance to be slowed.

[4] Heffernan's research was the basis for vaccine programmes against haemophilus influenzae type b, pneumococcus and meningococcus.

[5] She also represented New Zealand at regional meetings in the Pacific, and at the World Health Organization's workshop on Antimicrobial Resistance Surveillance.

[3][4] In the 2020 New Year Honours, Heffernan was appointed a Companion of the New Zealand Order of Merit, for services to health.