We’ve already talked a little bit about meningitis, which technically means inflammation of the tissues covering the brain and spinal cord. Not ALL meningitis is caused by infection, but most is. You may know someone who has had viral meningitis, which is miserable but very very rarely dangerous. Bacterial meningitis, on the other hand, is a very sinister beast. Neisseria meningitides is one of the scariest meningitis bugs out there, carrying a mortality rate of around 40% untreated and still 10-15% WITH MODERN MEDICAL TREATMENT. About 20% of survivors are left with permanent brain damage. N. men doesn’t just cause meningitis either. It can cause meningococcemia, which is where the infection spreads through the blood stream all over the body. This condition carries mortality rates similar to meningococcal meningitis.
At this point, we can’t protect your kids from all strains of this deadly disease but we’ve got the most common ones covered. Menactra was first licensed in 2005 and is administered at age 11 with a booster at age 16. This is because n. men tends to hit either in infancy or in early adulthood and is most common in college freshmen and new military recruits who are living in a communal situation (e.g. the dorm). Immunity in adults lasts about 5-10 years, so if teens get both doses, they’re covered through their most susceptible years. Why don’t we give this one to babies if infants also get the disease? That was one of the first questions I had about vaccines that got me probing into the literature in the first place. Turns out most infants who contract this disease are most commonly infected with B strains, which aren’t covered by Menactra. Only recently (in 2015 to be specific) did we have a vaccine against B strains licensed in the US. As of now, we give this new vaccine to 16 year olds in two doses spaced a month apart. Its efficacy is honestly not that stellar but it has a very low incidence of adverse reactions (Bexsero has a much better safety record than its competitor, Trumenba) and it’s certainly better than nothing. This one hasn’t been tested in infants, but it could be in future.
Another reason we don’t vaccinate infants is a practical one – most cases of meningococcal disease in babies are in infants under 6 months of age and babies that young don’t seem to mount a very good response to this type of vaccine. The subject of vaccinating babies comes up at ACIP regularly and there are advocates on both sides of the fence but at this point, our best information tells us that the risks of adverse reaction do not outweigh the benefits since universal vaccination likely would not do much to decrease mortality from this disease, given its rarity and the vaccine’s low efficacy in young infants. That’s right, folks. We don’t give vaccines to all comers unless we feel assured of both efficacy and safety. More on this topic in another post.