A few years after New Zealand downgraded its vaccine programme against pneumococcal disease, cases of the potentially fatal childhood disease were three times higher than in Australia, new research has found.
A study released on Wednesday morning found Pharmac's decision to amend the pneumococcal vaccine switch will provide better protection against invasive pneumococcal disease (IPD) - but warns it may take a few years to see significant improvements.
Pneumococcal disease is caused by the common bacteria streptococcus pneumoniae and at the more minor end, it can cause localised ear or sinus infections. However, if the bacteria gets into the blood, it can cause IPD, resulting in a severe form of pneumonia, bacteraemia (blood infection) and meningitis, potentially affecting the heart muscle, joints and abdomen.
In 2022, there were 41 deaths due to IPD in New Zealand. The rise in cases prompted Pharmac to provide broader protection against the potentially fatal childhood disease.
Previously the vaccine, called PCV13, was only funded for high-risk people. But from December 2022, access was widened, allowing the vaccine to be used as part of the childhood immunisation programme, instead of PCV10.
New Zealand's immunisation schedule previously included a PVC13 vaccine but it reverted to PCV10 in 2017 due to low IPD cases at the time in order to redirect funding into other vaccines. Australia's national immunisation schedule has funded a PVC13 vaccine since 2011.
A University of Otago, Christchurch study, published in The Lancet Western Pacific medical journal, compared IPD case numbers in Australia and New Zealand over a five-year period from 2017-2021.
The study found the overall IPD rate in Aotearoa for preschool children increased during this time period, particularly cases of the potentially life-threatening 19A IPD serotype.
While ethnicity-adjusted IPD rates for children under two were similar for both countries between 2017-2020, case numbers in New Zealand rose sharply in 2021. The research found NZ children under two years of age were found to be more than three times higher than in Australia, with 64.3 percent of cases identified as serotype 19A.
"New Zealand's proportion of serotype 19A IPD cases increased from 11.5 percent to 29.5 percent for children under five years old, whereas Australian rates remained static at 5 percent," the study said.
Paediatric infectious diseases specialist at the University of Otago, Christchurch and the study's co-author Professor Tony Walls said the results reinforce the timeliness of Pharmac's decision to switch to the PVC-13 vaccine.
"The World Health Organization recommends that a switch in the vaccine used in any national PCV programme should be considered if the epidemiology of IPD changes significantly. This study, the first undertaken comparing IPD rates in both countries, proves that significant change was occurring in New Zealand, and that an upgrade to the PVC-13 vaccine was urgently required," Professor Walls said.
"Pneumococcal disease is currently the world's number one vaccine-preventable cause of death among infants and children younger than five years of age. This decision will help arrest the concerning rise in IPD case numbers in this country and better protect our young children from the worrying and life-threatening risks the disease poses."
University of Otago, Christchurch post-doctoral research fellow and study co-author Nienke Hagedoorn said young Pasifika and Māori children in Aotearoa are disproportionally affected, as are other vulnerable groups.
The study found the Indigenous Australian population experienced the highest rates of the disease, followed by Pasifika and New Zealand Māori.
"The risk of invasive pneumococcal disease for Pasifika children and tamariki Māori is almost three times higher than the risk for other ethnicities in New Zealand. However, the study shows rates of serotype 19A are also increasing among New Zealanders aged over 65 as well," Hagedoorn said.
"It's important for surveillance to also monitor serotype and IPD incidence in older New Zealanders to inform ongoing policy on pneumococcal vaccines. Their burden of disease should also be considered as the influence of infant vaccinations can also provide indirect immunity in older age groups."
Prof Walls warns the recent switch from PVC10 to PVC13 may take a few years to significantly reduce our burden of disease.
"Catch-up immunisations for children under five are not part of the PVC programme change, therefore those who received PVC10 may not have adequate protection against serotype 19A," he said.
The study authors advise that improving immunisation coverage nationwide, particularly in high-risk groups, should be a key aspect of any plan to reduce the impact of IPD due to stereotype 19A.
