This is the short version. See the long version with references here.
What are the “meningitis vaccines”?
There are two basic types of meningitis: viral and bacterial. There are no vaccines targeting viral meningitis. There are three vaccines targeting causes of bacterial meningitis: HiB (Weekly Topic 05), pneumococcal, and meningococcal (Weekly Topic 03).
There are two types of pneumococcal vaccines: conjugated (PCV) and unconjugated (PPSV).
What is pneumococcus?
Streptococcus pneumoniae, often referred to as pneumococcus, is a bacterium. It may have a capsule or not have a capsule. The structures on the capsule determine its serotype. It can adopt or change its capsule, thus changing its serotype. This is called “serotype switching.” There are over 90 serotypes. Which serotypes are most common and how many are resistant to drugs varies significantly by geographic location.
S. pneumoniae is normally carried by healthy people with no symptoms (asymptomatic carriers). Depending on the population, 5-60% may be carriers. About half of babies become carriers by age 6 months and almost 100% become carriers by age 2 years. Carriage is more common after viral infection (especially influenza). Asymptomatic carriage typically lasts months. Because carriage is so common, disease is relatively rare.
S. pneumoniae is a common cause of otitis media (middle ear infection). If disease develops, complications are uncommon but include pneumonia, meningitis, and sepsis.
How can I prevent or treat pneumococcal infection in my child?
Conditions that make an individual more susceptible to pneumococcal disease include recent viral infection, immune suppression, and a generally unhealthy lifestyle. The best prevention is to boost the immune system, avoid people who are sick, and engage in a generally healthy lifestyle. The vitamin C protocol for pertussis may help treat pneumococcal infection.
How effective are the vaccines at preventing asymptomatic carriage?
Neither PPSV nor PCV decrease asymptomatic carriage. Some studies find that asymptomatic carriage increases with PCV. After PCV, vaccine-targeted pneumococcal serotypes decrease but non-vaccine serotypes increase (called “serotype replacement”), and carriage of other species of bacteria (including HiB, M. catarrhalis, and Staphylococcus aureus) increase. FluMist vaccination also increases carriage of S. pneumoniae and Staph.
How effective is the pneumococcal vaccine?
The pneumococcal vaccines are said to protect against otitis media (ear infections), pneumonia, meningitis, and sepsis. If the infection moves past the ears and/or lungs to infect the normally sterile linings of the lungs (empyema), meninges of the brain (meningitis), or the blood (sepsis), it’s referred to as invasive pneumococcal disease.
1. Special Populations. The vaccine is less effective in the populations who are most susceptible to complications from pneumococcus: immunosuppressed patients, patients with frequent respiratory infections, the elderly, and young children. Some studies found that vaccination of children with PCV was followed by an increase in drug-resistant pneumococcal infections in young children and/or the elderly.
2. Serotype Replacement. S. pneumoniae can change its serotype after infecting someone. When one serotype is targeted by a vaccine, the bacteria can simply infect the vaccinated child and then switch its serotype in order to bypass the child’s defenses. This is called “vaccine escape.” The newest PCV targets 13 serotypes, but there are over 90 pneumococcal serotypes. After vaccination, researchers noted significant serotype replacement, which has often resulted in no change or an increase in the total number of IPD cases. Some studies have also shown an increase in antibiotic resistance.
3. Otitis Media (Ear Infection). At least 60% of acute otitis media (AOM) is viral, pneumococcus makes up about 25% of all AOM causes, and over 80% of children with AOM recover without antibiotics. Studies have found either a 6-7% decrease or no change in AOM; no change in recurrent AOM; and an increase in other serotypes (serotype replacement) and other species of bacteria which are more likely to be antibiotic resistant and harder to treat. In other words, the vaccine may or may not affect the rate of AOM but increases the likelihood that AOM will be difficult to treat.
4. Invasive Pneumococcal Disease (IPD). Studies vary significantly, with results ranging from a decrease to no change to an increase in IPD; however, serotype replacement is common. Disease caused by non-vaccine serotypes is more severe and some studies report it is also more likely to be antibiotic-resistant and more difficult to treat. The worst effects occur in the very young, the very old, and those who’ve received the most doses of the vaccine.
a. Pneumonia. In children, studies find slight decrease, no change, or significant increase in overall pneumonia cases; extensive serotype replacement; and an increase in empyema (severe pneumonia). In other words, the vaccine may or may not affect the rate of pneumonia in children, but it increases the rate of severe pneumonia that is difficult to treat. In older adults, pneumococcal vaccination is ineffective.
b. Meningitis. Studies seem to agree that meningitis rates decrease, but this drop in meningitis occurs alongside an increase in pneumonia and sepsis.
c. Sepsis. Studies have found decrease, increase, or no change in sepsis rate; extensive serotype replacement; and increases in severe disease, drug-resistant cases, and cases caused by other bacteria (notably E. coli). In other words, the vaccine may or may not affect the sepsis rate, but makes it more difficult to treat.
What are the risks of the vaccine?
A short list of the most concerning risks includes:
• autoimmune diseases
• local reactions that will be mistaken for infection and result in unnecessary hospitalization and antibiotic use
So what’s the bottom line?
S. pneumoniae is so common that almost 100% of the population carries it and develops some degree of immunity by age 2. There are over 90 serotypes, and the bacteria easily change their serotype to avoid the host’s vaccine-induced defenses. The vaccine may increase asymptomatic carriage not only of S. pneumoniae but also of other bacteria and so cannot contribute to herd immunity and may actually pose greater risk to the herd. The vaccine is said to protect against ear infections, pneumonia, meningitis, and sepsis, but may actually be ineffective for all of these purposes due partly to serotype switching and serotype replacement, and partly to increases in other bacteria. The serotypes not covered by the vaccines are more dangerous, and so the proportion of serious infections is higher in vaccinated children than in unvaccinated children. Because it is mostly ineffective, the risks, no matter how mild, outweigh the benefit.