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No herd immunity benefit from meningococcal B vaccine

Health & Medical

Meningococcal B vaccinations are highly effective at protecting those immunised but do little to prevent the spread of the deadly disease, a large-scale South Australian study has found.

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Led by the University of Adelaide’s Robinson Research Institute professor Helen Marshall, the results of the study – known as B Part of It – are published today in the New England Journal of Medicine.

The immunity study of almost 35,000 school students was rolled out in stages across South Australia between 2017 and 2018 and examined if the recommended meningococcal B vaccine reduced the spread of meningococcal bacteria in teenagers by immunising a large group.

Professor Marshall said it showed “good protection” against the disease in those vaccinated, but did not show an overall reduction in the proportion of adolescents carrying the bacteria.

“You have to be vaccinated to be protected. The vaccine is not going to reduce the number of people carrying the bacteria and therefore less transmission and therefore a herd immunity benefit,” she said.

Professor Marshall said, in the three years since the study began, there had not been a single case of meningococcal disease among participants.

She said this was compared with 12 cases in the same age group in the two years prior to the study.

“On average, one in every 10 children with meningococcal disease dies from it,” professor Marshall said.

The results from the B Part of It study, which is among the largest meningococcal B herd immunity studies ever conducted, will be used in Australia and globally to assess the cost-effectiveness of meningococcal B immunisation programs for children and young people.

Professor Marshall said the study could shape local and global policy around meningococcal B.

“When decisions are being made about the age groups to vaccinate, the important message from our study is to look at your country’s epistemology and understand the age groups at highest risk. Provide the vaccine to those age groups, rather than relying on the potential for a herd immunity impact,” she said.

Meningococcal B is an acute bacterial infection that kills approximately 10 per cent of those infected and causes permanent disabilities in about 20 per cent of cases.

Those most at risk are babies and children up to the age of five years, as well as people aged 15 to 24 years.

However, adolescents can carry the meningococcus bacteria in the back of the throat without developing the disease.

There are five sub- groups of meningococcal: A, B, C, W and Y.

Study participants included high school students from years 10 to 12.

All participants had their throats swabbed at the beginning of the study before being split into two groups. One group was given two vaccines. After 12 months all participants were re-swabbed before the second group received their vaccines.

The study identified a number of high-risk behaviours associated with carrying meningococcal strains. These included smoking cigarettes and kissing.

Older school students, school boarders, and those who had recently had a cold or sore throat were also more likely to carry the meningococcus in their throat.

The B Part of It study was funded by GlaxoSmithKline (GSK).

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