Secondary and exploratory outcomes
Independent risk factors associated with N. meningitidis carriage in the study participants at the 1-year mark included smoking cigarettes or hookah, intimate kissing within the last week, and being in grades 11-12, as opposed to grade 10.
The vaccine had no significant impact on the carriage rate of the hypervirulent New Zealand serogroup B strain. Nor was there a vaccine impact on carriage density, as Mark McMillan, MD, reported elsewhere at ESPID 2019. But while the 4CMenB vaccine had minimal impact upon N. meningitidis carriage density, it was associated with a significant 41% increase in the likelihood of cleared carriage of disease-causing strains at 12 months, added Dr. McMillan, Dr. Marshall’s coinvestigator at University of Adelaide.
The ongoing B Part of It School Leaver study is assessing carriage prevalence in vaccinated versus unvaccinated high schoolers in their first year after graduating.
In addition, the B Part of It investigators plan to prospectively study the impact of the 4CMen B vaccine on N. gonorrhoeae disease in an effort to confirm the intriguing findings of an earlier large, retrospective New Zealand case-control study. The Kiwis found that recipients of an outer membrane vesicle MenB vaccine had an adjusted 31% reduction in the risk of gonorrhea. This was the first-ever report of any vaccine effectiveness against this major global public health problem, in which antibiotic resistance is a growing concern (). Dr. Marshall reported receiving research funding from GlaxoSmithKline, which markets Bexsero and was the major financial supporter of the B Part of It study.
But wait a minute...
Following Dr. Marshall’s report on the B Part of It study, outgoing ESPID president Adam Finn, MD, PhD, presented longitudinal data that he believes raise the possibility that protein-antigen vaccines such as Bexsero, which promote naturally acquired mucosal immunity, may impact on transmission population wide without reliably preventing acquisition. This would stand in stark contrast to conjugate meningococcus vaccines, which have a well-established massive impact on carriage and acquisition of N. meningitidis.
It may be that in studying throat carriage rates once in individuals immunized 12 months earlier, as in the B Part of It study, investigators are not asking the right question, proposed Dr. Finn, professor of pediatrics at the University of Bristol (England).
His research team has been obtaining throat swabs at monthly intervals in a population of 917 high schoolers aged 16-17 years. In 416 of the students, they also have collected saliva samples weekly both before and after immunization with 4CMenB vaccine, analyzing the samples for N. meningitidis by polymerase chain reaction. This is a novel method of studying meningococcal carriage they have found to be both reliable and far more acceptable to patients than oropharyngeal swabbing, which adolescents balk at if asked to do with any frequency ().
Dr. Finn said that their findings, which need confirmation, suggest that N. meningitidis carriage is usually brief and dynamic. They also have found that carriage density varies markedly from month to month.
“We see much higher-density carriage in the adolescent population in the early months of the year in conjunction, we think, with viral infection with influenza and so forth,” he said, adding that this could have clinical implications. “It feels sort of intuitive that someone walking around with 1,000 or 10,000 times as many meningococci in their throat is more likely to be more infectious to people around them with a very small number, although this hasn’t been formally proven.”
He hopes that thewill help provide answers. The study is randomizing 24,000 U.K. high school students to vaccination with the meningococcal B protein–antigen vaccines Bexsero or Trumenba or to no vaccine in order to learn if there are significant herd immunity effects.
Dr. Finn’s meningococcal carriage research is funded by the Meningitis Research Foundation and the National Institute for Health Research. Dr. Marshall reported receiving research funding from GlaxoSmithKline, the major sponsor of the B Part of It study.