In this entry, I would like to review the impact that severe infections from a common pneumonia bacterium can have on asthmatics and discuss some recent research on how this has changed immunization schedules for asthmatics.
This new research has changed recommendations from the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC), the federal agency that monitors disease outbreaks and provides evidence-based recommendations on immunization (for kids and adults). Setting aside recommendations that apply to all individuals (especially infants and young children), there are often some modifying circumstances that have to do with health status that change recommendations - if a vaccine should be administered or not, whether a booster should be given, etc. Recent research on infections caused by a common respiratory bacterium Streptococcus pneumoniae ('pneumococcus', in common usage) has expanded the indication for immunization against this bug to asthmatics.
What is the pneumococcus and what does it do?
The respiratory tract, unlike other organ systems, such as the cardiovascular (e.g. heart) or genitourinary (e.g. kidney) systems, is regularly exposed to the outside environment through the air we breathe. This exposure includes not just bacteria and viruses but also varied particulate matter - dust, exhaust particles, pollens, among others. Interestingly, the type of tissue that lines the nose, sinuses, and parts of the throat is very similar to that in the breathing tubes of the lungs. As such, the "respiratory tract," from a medical standpoint, includes the so-called "upper" and "lower" parts: the upper tract includes the nose, sinuses, throat, voice box, and middle ear; the lower tract includes the windpipe and smaller airways deeper in the lungs. Thinking of these parts of the respiratory tract together is important in terms of infections, as many bugs that affect the respiratory tract can affect upper and lower parts.
The main classification of 'bugs' are viruses and bacteria. Over 90% of 'common colds' are caused by viruses. Strep throat, for example, is caused by a bacterium. One bacterium in particular, pneumococcus, is very versatile in the respiratory tract, and can cause sinusitis, otitis media (a middle ear infection), and pneumonia. In fact, pneumococcal pneumonia is the most common cause of pneumonia that occurs in the community (versus pneumonia acquired in the hospital). In some cases, infections with pneumococcus can be severe, as they can spread from to the bloodstream and other places. Any infection with pneumococcus that spreads to the blood or spinal fluid ('meningitis') is severe and can be life threatening. It is well known that some individuals are more prone to these severe infections - people with a weakened immune system (for varied reasons including being on chronic steroids), with chronic lung disease (such as emphysema or COPD), and individuals without a spleen. These populations are those that stand the most to benefit from a vaccine against pneumococcus - either because they are more prone to getting an infection or can't effectively fight an infection if it sets in.
Changes in immunization recommendations for vaccination against pneumococcus
Until recently, there were well-founded recommendations that individuals with the disorders mentioned above get vaccinated at an early age (before age 65) with the pneumococcal vaccine ('the pneumonia vaccine'). Notably, people with chronic asthma were excluded from this list, as there was no evidence to show that it was effective. This has changed due to a recent study that showed that individuals who developed severe/life-threatening pneumococcal infections were more likely to have asthma. The researchers performed a review of serious pneumococcal cases in a large Minnesota county and compared these to individuals that did not have serious pneumococcal disease who were matched by gender and birthday (also living in the same county). The researches found that all individuals with serious pneumococcal infections were nearly 2.5 times more likely to have asthma. When they looked at adults, those with severe pneumococcal disease were nearly 7 times more likely to have asthma. These results demonstrated that asthmatics, especially adult asthmatics, are significantly more likely to get severe infections from pneumococcus.
With these recent results in hand, the ACIP of the CDC changes their formal recommendations for immunization against pneumococcus - in late 2008 they released a preliminary amendment to their prior recommendations that now includes asthma as a predisposing condition for which adults (age >19) should receive the pneumonia vaccine. This modification will be included in the ACIP 2009 Recommended Adult Immunization Schedule, to be released in January 2009.
While it is not clear that asthmatics have a weaker immune system (as does someone without a spleen), it is now clear that there are features of the airways in asthmatics that not only predispose them to pneumococcal infection, but especially more severe infection. You should ask your doctor about whether the pneumonia vaccine is right for you.