Studies: MenB vaccine prevents illness but not carriage rates

Meningococcus bacteria in spinal fluid

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Two studies concerning post-licensure use of the meningococcal group B vaccine published today in the New England Journal of Medicine show the vaccine prevents disease among recipients, but it does not affect pharyngeal carriage of the bacterium Neisseria meningitidis on a population level.

The studies are based on data collected from the United Kingdom and Australia.

Filling in previous data gaps

"These studies helped answer unanswered questions we had about the vaccine, including how well it works and if it offered herd protection," said Lee Harrison, MD, the associate chief of epidemiology and education at the University of Pittsburgh, in an interview. "When the vaccine was licensed, it was only based on safety and immunogenicity data."

Harrison, along with David S. Stephens, MD, of Emory University in Atlanta, wrote a commentary on the studies, which they said were impressive in scope and comprehensive.

In 2013, GlaxoSmithKline's Bexsero (4CMenB) became the world's first vaccine against group B meningococcal disease meant for use in infants and at-risk adults. In 2015, the United Kingdom was the first country to inoculate infants with Bexaro at 8 and 16 weeks of age, with a booster dose given at 12 months.

Within 3 years, new data from Public Health England (PHE) in the first study published today show the vaccine lowed group B meningococcal disease incidence by 75% in age-groups eligible for vaccination. The adjusted vaccine effectiveness against meningococcal group B disease was 52.7% (95% confidence interval [CI], −33.5 to 83.2) with a two-dose priming schedule for infants and 59.1% (95% CI, −31.1 to 87.2) with a two-dose priming schedule plus a booster at 1 year).

Protection from the booster dose at 12 months lasted at least 2 years, the authors said.

In their commentary, Harrison and Stephens wrote, "Although the confidence intervals for the estimate of vaccine effectiveness were wide and do not exclude 0% (−31.1 to 87.2), taken together, the results suggest a substantial effect of 4CMenB on capsular invasive meningococcal group B disease in children in the United Kingdom. This is good news and highlights the real-world effectiveness of 4CMenB."

In a press release, lead author of the UK study, Shamez Ladhani, PhD, a consultant epidemiologist at PHE, said, "The implementation of the MenB vaccine in 2015 is a great success; it is already saving lives and means fewer parents and young children will experience this devastating illness."

PHE estimates that 92% of infants in 2018 completed MenB vaccination doses by their first birthday.

No reduction in bacterial carriage

The second study looked at how and if 4CMenB reduced pharyngeal carriage of Neisseria meningitidis on 35,000 teenagers, ages 15 to 18, in south Australia. Carriage is used to estimate herd protection, as the disease-causing Neisseria meningitidis (group A, B, C, W, X, or Y) can be transmitted by a person with no symptoms.

The teenagers were vaccinated with 4CMenB at the start of the study or 12 months later. Researchers found no difference in the prevalence of carriage of disease-causing N meningitidis between the vaccination group (2.55% prevalence; 326 of 12,746) and the control group (2.52%; 291 of 11,523) (adjusted odds ratio, 1.02; 95% CI, 0.80 to 1.31; P = 0.85).

"Our study has shown good protection was provided by the meningococcal B vaccine against meningococcal disease in those vaccinated but did not show an overall reduction in the proportion of adolescents carrying the bacteria, including the B strain," said Helen Marshall, PhD, lead author of the study, in a press release from the University of Adelaide.

In many parts of the world, meningococcal group B disease is a leading cause of childhood illness and death, causing meningitis and blood poisoning, but not in the United States. Harrison explained that the incidence today is reduced by 90% compared with the mid-1990s.

"Only high-risk individuals are recommended to receive the vaccine," said Harrison, noting that the MenACWY vaccine is routinely recommended for all 16- to 23-year-olds in the United States.

The new studies will not change those recommendations, Harrison said, because the burden of group B is so low in the States.

"Incidence of meningococcal disease depends on so much: the circulating strain, population immunity, and behavioral risk factors," he said.

See also:

Jan 23 N Engl J Med UK study

Jan 23 N Engl J Med Australia study

Jan 23 N Engl J Med commentary

Jan 23 PHE press release

Jan 22 University of Adelaide press release

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