Neisseria menigitidis, or meningococcus, is a bacteria often carried in the nose and throat without symptoms. It can be spread by droplets coughed or sneezed out by an infected person or by a carrier; many outbreaks of meningococcal infection occur in people living in close quarters (like schools, colleges, and military installations). It takes 1-10 days (most often 4 days or less) after exposure to show symptoms; patients are usually contagious until they have been treated for at least 24 hours.
Meningococcal infection can cause meningitis, sepsis, or both. Oddly, someone with meningococcal infection with meningitis may do better than s/he would with sepsis and no meningitis; this does not always happen, though. Signs of meningococcal infection may include fever with chills and a rash; the classic rash of meningococcal infection is "petechial", caused by tiny blood clots just below the skin surface. In severe cases the infection can result in shock and death within a few hours even if treated. Also, as antibiotics kill the meningococci, the breakdown products of the dead bacteria can cause inflammation and abnormal blood clotting. Much of the damage from meningococcal sepsis comes from blood clotting in the wrong places and blocking blood flow to large parts of the body: many patients with meningococcal sepsis lose fingers or toes, and sometimes hands, feet, or larger parts of their arms or legs, because of clots blocking blood flow to those areas. About 1 out of every 100,000 people per year are infected by meningococcus. Of every 100 patients infected, 10 to 14 die, and up to 19 out of 100 survivors will have permanent damage.
In the past penicillin G has been sufficient treatment for meningococcal infection. However we have seen strains of meningococcus in recent years that are resistant to penicillin G; these must be treated with other antibiotics such as the third-generation cephalosporins. Antibiotics for someone with possible meningococcal infection are chosen initially according to whether or not resistance has been seen in previous patients with meningococcus, since there is not enough time to culture the patient's own bacteria and test different antibiotics against it.
There are many different groups or "serotypes" of meningococci, at least 8 of which can infect people. The most common infectious groups are labelled A, B, C, X, Y, Z, 29-E, and W-135 (and no, I don't know exactly how the labels were assigned...). Groups B and C are the groups most often seen in the United States. Unfortunately we do not yet have a good vaccine for group B. We do, however, have vaccines available that protect against groups A, C, Y, and W-135. They are usually given as a combination vaccine, where a single dose protects against all four groups; in special cases a vaccine can be given to cover just one of the groups.
The older vaccine (Menommune®) can be given to children 2 years of age or older. There are versions of this vaccine which protects only against single group meningococcus. They are used most often to help control epidemics rather than for general protection. The A vaccine will provide immunity to patients 3 months or older, but the C vaccine works well only in children 2 years or older. (This is why we can't routinely give Menommune to kids under age 2.) The newer vaccine (Menactra®), which just became available, also protects against groups A, C, Y, and W-135, but works a bit differently. Menactra is licensed in the United States for use in people age 11 to 55, but similar single-group vaccines for group C are available for infants and children in Europe.
The Advisory Committee on Immunization Practices and the Centers for Disease Control and Prevention recommends that all children be vaccinated with the new meningococcus vaccine at age 11 or 12, and (as they have in the past) that all students entering college be vaccinated against groups A, C, Y, and W-135. The American Academy of Pediatrics also recommends that all entering college students get the vaccine, and many colleges and universities require their new students to be vaccinated. Travelers to countries where meningococcus is more common should also receive the vaccine, as should patients whose spleens have been removed or no longer work properly (such as patients with sickle-cell anemia, whose spleens eventually fail). Certain groups of people, such as military personnel, also routinely receive the vaccine.
As of February, 2008, the US Food and Drug Administration and the US Centers for Disease Control and Prevention had information on 26 confirmed cases of Guillian-Barre syndrome that developed within 6 weeks after receiving the meningococcal vaccine Menactra®.
Guillian-Barre syndrome is a disorder affecting nerves, which usually occurs several days to weeks after a mild infection, a vaccination, or occasionally after surgery. How Guillian-Barre syndrome happens isn't well known, but in almost all cases the myelin sheath (the "insulation" for the nerves) is damaged in scattered places on scattered nerves. The symptoms and signs of Guillian-Barre syndrome include weakness and partial numbness, usually showing up first in the legs and moving to the arms, and symmetric on both sides of the body. The reflexes (like the knee jerk) often disappear. If the syndrome is severe enough the muscles of the face, mouth, and throat are also affected, and some patients may have enough trouble breathing that they have to be put on a ventilator for a while. (According to the FDA and CDC, the patients who developed the syndrome after Menactra® had mild problems and did not need help breathing.) There are effective treatments for the syndrome.
The first five cases of Guillian-Barre syndrome occurred after 2.500.000 doses of Menactra had been given. Five cases of Guillian-Barre syndrome out of 2,500,000 doses of vaccine is about what you would expect from pure chance. The CDC is still gathering information and reports on incidents of Guillian-Barre syndrome following vaccination with Menactra.
This does not mean that Menactra® causes Guillian-Barre syndrome. As always, whether you need Menactra® -- or any other vaccine -- is for you and your doctor to discuss, and depends on which bothers you more: the chance of getting Guillian-Barre syndrome from the vaccine (from the data we have right now, about 1 in 500,000) or the chance of being infected by meningococcus (1 in 100,000). I received Menactra® prior to recent travel abroad (including several areas where meningococcus infections have been reported) and even after the FDA/CDC announcement: that's in part because of the 11 or 12 patients with meningococcal meningitis or sepsis I have seen and taken care of in my career -- of which one left the hospital alive (minus one hand, but alive).