Meningococcal serogroup B (MenB) vaccines received FDA approval based on blood tests indicating immune response (immunogenicity) to the particular strains found within the vaccine. Meningococcal serogroup B strains, however, are quite diverse, and as a result, vaccine effectiveness is difficult to assess.
Moreover, with meningococcal serogroup B disease rates at historical lows and disease outbreaks sporadic even prior to the licensing of TRUMENBA (MenB-FHbp) and BEXSERO (MenB-4C) vaccines, data on the effectiveness of meningococcal group B vaccines was considered almost impossible to attain. Immunogenicity, however, is not necessarily indicative that either available Men B vaccine is, in fact, effective against any of the various meningococcal group B strains that may be circulating in the environment.
While ACIP recommends that all persons with complement component deficiencies as well as those taking the medication eculizumab (Soliris®) be vaccinated with a meningococcal conjugate vaccine as well as a Men B vaccine, all meningococcal vaccine package inserts state that these individuals will continue to remain at high risk of meningococcal disease even if they develop antibodies following vaccination. Several published studies have reported on the failure of meningococcal vaccines to offer protection in this particular susceptible population.
According to unpublished data submitted by Pfizer to ACIP in 2015, blood antibody levels believed to be indicative of a protective immune response decrease quickly after three doses of TRUMENBA (MenB-FHbp) vaccine. This data reported that within four years, only about 50 percent of vaccine recipients had blood antibody levels above or at the lowest acceptable level indicative of an immune response but only to three out of four of the meningococcal serogroup B vaccine strains tested.
In BEXSERO (MenB-4C) pre-licensing immunogenicity trials, the three antigen strains found within the vaccine were measured in college students in the United Kingdom at 1 and 11 months following the administration of two doses of the vaccine. At one month, 88 percent of vaccine recipients had an immune response considered to be protective, however by 11 months, this number decreased to only 66 percent. The long-term effectiveness of BEXSERO vaccine is unknown at this time.
In late 2013 – early 2014, and prior to FDA approval, the FDA and CDC approved BEXSERO (MenB-4C) for use during an outbreak of meningococcal serogroup B invasive disease at Princeton University. In 2016, a published study reported that nearly 34 percent of vaccine recipients had no evidence of a protective immune response against the particular meningococcal serogroup B strain responsible for the outbreak at Princeton University eight weeks following the second dose. While no additional cases of meningococcal serogroup B invasive disease occurred among vaccine recipients at Princeton University, one additional fatal case was reported during the same time period in a student attending another university who had a history of close contact with several Princeton University students. This additional case provided evidence that the vaccine did not eliminate N. meningitidis serogroup B carriage and that vaccinated individuals who carry serogroup B meningococci in their nasopharyngeal area could still transmit the bacteria and potentially cause invasive disease in others.
A 2017 published study examining meningococcal carriage during an outbreak of meningococcal serogroup B at a large university in Oregon found that neither BEXSERO (MenB-4C) nor TRUMENBA (MenB-FHbp) had any impact on meningococcal nasopharyngeal carriage reduction and that implementing vaccine programs to target meningococcal serogroup B did not result in herd protection. High vaccination rates coupled with the use of preventative antibiotics in persons with a history of close contact to a person diagnosed with invasive meningococcal disease was recommended during an outbreak, with study authors encouraging that further research be completed to determine the effectiveness, coverage, and duration of protection afforded by both MenB vaccines.
