What it prevents: This vaccine protects against several different types of bacteria, known as streptococcus pneumoniae, that usually live harmlessly in your nose and throat. An overgrowth of these pneumococci, however, is one of the most frequent causes of ear infections or more serious (and even deadly) infections in the lungs, blood stream, and central nervous system. Since its introduction in 2000, this vaccine has drastically reduced rates of ear infections and the need for ear tubes in children, as well as the number of more serious pneumococcal infections.

When it’s given: PCV is given in four shots: at 2 months, 4 months, 6 months, and between 12 and 15 months.

What you may have heard: The original vaccine used to prevent against the seven most common types of pneumococci (PCV7). In 2010, however, a newer version (PCV13) became available, protecting children against the 13 most common types of the bacteria, making the vaccine even more effective. This is critical, especially since some of these bacteria that the vaccine protects against have become resistant to antibiotic treatment.

Side effects: The vaccine may cause soreness or redness at the injection site, as well as a decrease in appetite and drowsiness. About 20 percent may have a fever over 100.3 degrees F. In extremely rare cases (1 in 10,000) a child may experience a fever-related seizure after the vaccine.