Herd Immunity for Pnuemonia

By Richard P. Holm, MD

The word pneumonia was said by Hippocrates himself to have been "named by the ancients" before him. As old as it is, pneumonia is still a cause of great human suffering, but we now have better weapons to fight it.

In a small percentage of cases, especially in the immunocompromised, a bacterial lung infection can follow several days after a common cold. Symptoms then would change from a dry cough into a productive cough, creamy-sometimes-rusty-sputum, shaking chills and sweats, and chest pain. It's important to note that antibiotics for the common cold DO NOT prevent a secondary bacterial pneumonia, but antibiotics started after the bacteria grab ahold can be life-saving. It's all about the timing.

About 50 percent of pneumonia is due to the pneumococcus bacteria, now named
Streptococcus pneumoniae. Sir William Osler said in the late 1800s that pneumonia is "the captain of the men of death." Prior to antibiotics, more than 30% of all those hospitalized for a bacterial infection of the lung would die. With antibiotics, that number dropped precipitously, but still people do die of pneumonia. Mostly they are very young or very old, related of course to their undeveloped or weakened immune systems.

This July, the New England Journal of Medicine reported since 2000 there has been a huge drop in hospitalizations for pneumonia, with 12,000 fewer deaths every year especially in those older than 85. What's most amazing is it happened since the advent of routine childhood Streptococcus pneumoniae vaccination also called PREVNAR.

Although a similar and effective pneumonia vaccine, PNEUMOVAX, is available and highly recommended for those older than 65, or younger with lung disease or diabetes, it has not become routine. The authors of the study claim that it is the routine vaccination in children that's responsible for most of the reduction of pneumonia in the elderly. They call it herd immunity. Children vaccinated against pneumonia certainly are benefited, but also it profoundly protects the immune deficient adults around them.

Take home message: it is wise to have children and adults vaccinated against the dreaded Strep pneumoniae. Indeed, the "captain of the men of death" has been demoted by antibiotics and vaccinations; both modern developments of science fighting against an ancient disease.