A The Kids Research Institute Australia and Curtin University-led study has found the maternal whooping cough vaccine given to pregnant mothers in the second or third trimester significantly reduced babies’ risk of infection, protecting them at their most vulnerable age.
Whooping cough – or pertussis – is a highly contagious respiratory disease accounting for 70 to 90 per cent of hospitalisations and deaths in babies.
The severity of the disease prompted calls for government-funded interventions with a state vaccination program forming in 2014 which evolved into a federally funded National Immunisation Program (NIP) in 2018, for pregnant mothers with a vaccine recommended at 28 weeks gestation.
Bumping up vaccination numbers to 52 per cent, whooping cough cases dropped 66 per cent in babies up to six months of age in the first three years of the program.
Despite the program’s success, further research is needed to evaluate the most effective time for maternal vaccination and to measure any interference from the mother’s antibodies when babies receive their standard infant whooping cough vaccines.
The study, funded by the National Health and Medical Research Council (NHMRC) and the Western Australian Department of Health, examined data from 279,418 mother and infant pairs – representing a third of all births in Australia over four years – using health records from Western Australia, Queensland and the Northern Territory.
Of the sample, 51 per cent of women received their whooping cough vaccine around their late second trimester and third trimester of pregnancy.
Published this week in the journal Pediatrics, results showed maternal vaccines were beneficial to babies, protecting them up to six months of age – the most susceptible period for infection.
Results also suggested the maternal vaccine reduced effectiveness of babies’ third whooping cough vaccine dose, suggesting maternal pertussis antibody interference, yet this did not coincide with an increase of infection.
Co-author Associate Professor Hannah Moore, an epidemiologist from the Wesfarmers Centre of Vaccines and Infectious Diseases and Curtin University’s School of Population Health, said the study supported the government’s current maternal vaccine recommendations while also shedding new light on the impact of the mother’s antibodies on infant vaccine effectiveness.
"This study strongly suggests that mothers receiving their whooping cough booster shot around 20 to 28 weeks gestation would deliver the highest protection against whooping cough for their babies,” Associate Professor Moore said.
"It was interesting to note the mother’s antibodies impact on babies’ third vaccine dose which showed reduced effectiveness – a phenomenon called blunting – but that was not met with a higher incidence of disease, meaning there were still enough antibodies to protect the baby and fight infection despite some interference from mum’s antibodies.
“The outcome strongly supports the current whooping cough vaccination schedule, and I would urge pregnant mothers to get their pertussis booster vaccination to ensure their babies receive optimal protection from a devastating disease.”
The study Maternal pertussis vaccination, infant immunization, and risk of pertussis is available here.