June 4, 2026 — New Zealand — New research highlights a troubling mismatch in infant health: babies with older siblings are at greater risk of infectious illness, yet they are less likely to benefit from maternal vaccination during pregnancy.
Maternal immunisation against pertussis (whooping cough) and influenza is publicly funded and recommended in New Zealand for every pregnancy. These vaccines not only protect mothers but also transfer antibodies to babies, reducing their risk of infection and hospitalisation.
However, analysis of the Aotearoa Immunisation Register shows vaccination uptake declines with each pregnancy. In first pregnancies, 69% of mothers received the pertussis vaccine and 45% received influenza vaccination. By the fourth pregnancy, uptake dropped to 38% and 24%, respectively.
This decline leaves later-born babies doubly disadvantaged: they are more exposed to infections brought home by older siblings and less likely to receive maternal antibody protection. Studies confirm that later-born children face higher hospitalisation rates for respiratory illnesses and more prescriptions for contagious diseases early in life.
Researchers suggest that barriers such as time constraints, lower prenatal care in later pregnancies, and reduced awareness contribute to missed vaccinations. Expanding access through pharmacies, community midwives, and local health services has already shown promise in boosting uptake, particularly among Māori women.
Strengthening maternal vaccination in later pregnancies could help protect babies most at risk, ensuring that families with multiple children do not face preventable health disadvantages.
