Study Finds Vaccine Brings Big Drop in Pneumococcal Bacteremia

A new study shows a significant reduction in rates of pneumococcal bacteremia in young children since the introduction of the pneumococcal conjugate vaccine.

Children are known to be at increased risk of acquiring pneumococcal disease, but now a new study shows that the pneumococcal conjugate vaccine effectively and significantly reduces the incidence of these infections, especially in children.

Streptococcus pneumoniae bacteria can cause pneumococcal illnesses such as ear infections, sinus infections, bacteremia, and even meningitis. Those at highest risk of catching these infections are adults ages 65 and older, along with children under 2 years of age, particularly those in group childcare or with certain preexisting illnesses. While pneumococcal pneumonia is the most common illness caused by S. pneumoniae, pneumococcal bacteremia is a blood infection marked by fever and chills. In children these infections can lead to complications, and according to the Centers for Disease Control and Prevention (CDC), about one in 100 children under 5 years of age who have pneumococcal bacteremia die from their infection.

To prevent pneumococcal disease, the CDC recommends the pneumococcal conjugate vaccine for children younger than 2 years old as well as adults who are 65 and older. In young children, the vaccine is given in three doses starting at the age of 2 months. Past studies have found that at least one dose of the pneumococcal conjugate vaccine can protect eight in 10 babies from invasive pneumococcal disease, which would result in fewer ear infections and pneumonia cases. The original form of vaccine, known as PCV7, contained seven serotypes of pneumococcal bacteria. However, since 2010, the PCV13 vaccine containing 13 bacterial serotypes has been available, offering greater protection against pneumococcal infections.

While the CDC estimates that more than 30,000 cases of invasive pneumococcal disease and 3,000 deaths have been prevented during the first years of using PCV13, a new study from researchers at Kaiser Permanente Northern California shows that use of the vaccine has made childhood pneumococcal bacteremia a rare event altogether. The study, published in the journal Pediatrics, examined pediatric medical records of children between 3 months and 3 years of age from September 1, 1998 to August 31, 2014. The aim of the study was to gain a better understanding of the effects of implementing a routine immunization program that utilized PCV13 vaccines, starting in 2010. The study authors looked at 57,733 blood cultures collected during that period, and found that the routine administration of PCV13 resulted in a 95.3% reduction of S. pneumoniae bacteremia. In the period following the introduction of PCV13, the rate of pneumococcal bacteremia decreased from 74.5 per 100,000 children per year, to 10 per 100,000 children, and then to 3.5 per 100,000 children.

"As shown by time series analysis, the dramatic decline in S. pneumoniae bacteremia rates was clearly related to the impact of immunization," the study authors wrote. With the marked decrease in pneumococcal bacteremia, Escherichia coli, Salmonella spp, and Staphylococcus aureus are now the leading causes of childhood bacteremia cases in the United States, causing 77% of all bacterial blood infections within this population, say the authors. The CDC notes that most individuals who receive the pneumococcal conjugate vaccine experience no side effects, though those who do may experience mild redness, pain, or swelling at the injection site, along with other symptoms such as fever or headache.