Pregnant women are being urged to be vaccinated against whooping cough, following a five-fold increase in whooping cough deaths in New Zealand over the past year.
Three babies died from the infectious disease in New Zealand earlier this year, and research indicates the deaths were likely caused by an infant-mother immunity gap.
Lead author and University of Otago professor of women’s and children’s health Peter McIntyre said the immunity gap was caused by three factors.
"Physical distancing and border closures due to Covid-19 significantly reduced exposure to pathogens spread by the respiratory route.
"On the upside, that reduced infections, but the down side is that circulation of infections in the community, many of which did not cause symptoms, helps maintain population immunity, and that has been missing."
Despite being fully funded since 2013, Prof McIntyre said uptake of maternal whooping cough vaccination in pregnancy among those living in areas of high deprivation (particularly Māori and Pacific women) sat between 20% and 30%.
Vaccination was generally too low — a maximum of only 60% were vaccinated.
"To add to the immunity gap this creates among newborns born to unimmunised mothers, New Zealand has long-standing poor timeliness for the whooping cough vaccine doses at ages 6, 12 and 20 weeks — especially in areas of high deprivation. The timeliness of these immunisations deteriorated further during 2022."
These three factors could lead to a complete absence of protective antibodies in an increased proportion of mothers, and complete absence was in turn "the main risk factor" for fatal whooping cough in newborn infants.
Whooping cough has been a notifiable disease in New Zealand since 1996, and there have been 4-5 year peaks.
After an epidemic beginning in October 2017, all-age notifications decreased to 1206 in 2019, followed by record lows of 171 (2020), 41 (2021) and 18 (2022). But in 2023, 33 cases were notified by June 17.
"The cluster of three whooping cough deaths this year was tragic in so many ways.
Even if no more deaths occur during 2023, this translates to a five-fold increase in whooping cough deaths compared with any previous year in Aotearoa.
"In relative terms, this is double the number of infant whooping cough deaths which triggered a national emergency in England in 2012."
Study co-author and New Zealand Immunisation Taskforce chairman Dr Owen Sinclair said reaching as many pregnant women as possible so they have the whooping cough vaccine during pregnancy, was the only way to protect babies who were too young to receive even the first dose at age six weeks.
"This is a dangerous, but preventable illness — we need to be doing all we can to protect our vulnerable babies."
