Partially False: Bexsero Protects Against Many Meningitis B Strains — But 'Most' Depends Heavily on Where You Live

The claim is that Bexsero, the meningococcal B vaccine, protects against most strains of meningitis B bacteria. The reality is more complicated: protection is meaningful and sometimes substantial, but whether it covers 'most' strains depends entirely on which country you're in and which bacterial strains are circulating there.

Bexsero works by targeting four proteins found on the surface of many meningococcal B bacteria. The problem is that not all strains carry these proteins in the same way. According to the European Medicines Agency's assessment, predicted strain coverage in the UK sits around 73–88% — that's a reasonable claim to 'most.' But a systematic review published in the journal Vaccine found coverage dropping below 50% in some regions, meaning the vaccine could miss more strains than it catches depending on where you are.

Real-world data adds another layer of caution. Public Health England found actual vaccine effectiveness in UK infants at roughly 52–59% — lower than the lab-based predictions suggest. That's still a meaningful reduction in a devastating disease, but it's a long way from comprehensive protection.

The CDC is clear that no meningitis B vaccine covers all strains, and the NHS carefully avoids claiming Bexsero protects against 'most' strains universally. There's also a separate issue the claim ignores entirely: Bexsero only targets serogroup B bacteria. It offers zero protection against meningococcal groups A, C, W, or Y, or other bacterial causes of meningitis altogether.

This kind of misinformation spreads partly because health communicators — with good intentions — reach for simple, reassuring language when talking to worried parents. 'Protects against most strains' sounds clear and comforting. The geographic and strain-specific caveats that actually define the evidence get left behind. Watch for vaccine claims that don't specify a region or population — that missing context often changes the picture significantly.