@Delatron I just did some digging online and found the following studies which I asked AI to summarise, they seem to support what you said about 2 doses and 6 months (if you're not needing to get quicker immunity):
• Vaccine: Bexsero (4CMenB / MenB-4C)
• The study is specifically about Bexsero, not another MenB vaccine.
• In 2024, the US FDA changed the licensed adolescent Bexsero schedule from 0 and ≥1 month to 0 and 6 months for healthy adolescents and young adults.
• The CDC's Advisory Committee on Immunization Practices (ACIP) subsequently adopted the same recommendation.
• The reason for the change was that studies showed stronger antibody responses (better immunogenicity) when the second dose was given 6 months after the first, compared with the previous shorter interval schedule.
• The CDC paper explicitly states that the new schedule provides "improved immune protection".
• If rapid protection is needed, the US now recommends a 3-dose schedule (0, 1–2, and 6 months) rather than simply giving two doses one month apart.
• The evidence is based on serum bactericidal antibody (hSBA) responses, which is the accepted way MenB vaccines are assessed, rather than direct measurement of meningitis cases (the disease is too rare for practical efficacy trials).
• The UK and Europe have not yet changed the licence, so Bexsero remains licensed as 2 doses at least 1 month apart.
• Therefore, a 4-week interval is still an approved and evidence-based schedule in the UK, but newer US data suggest that a longer interval (around 6 months) may produce a stronger and potentially more durable immune response.
Key paper:
https://pmc.ncbi.nlm.nih.gov/articles/PMC11637420/
CDC recommendation update:
https://www.cdc.gov/mmwr/volumes/73/wr/mm7349a3.htm
Additional 2024 immunogenicity study comparing Bexsero schedules:
https://pmc.ncbi.nlm.nih.gov/articles/PMC11584413/