hello dear thanks for your query at HCM PNEUMOVAX 23 is a vaccine that is given as a shot. It helps protect you from infection by certain germs or bacteria which are called pneumococcus . PNEUMOVAX 23 is for people 50 years of age and older. It is also for people who are 2 years of age and older if they have certain medical conditions that put them at increased risk for infection. Illnesses or health problems may allow these germs to spread into the blood, lungs, or brain where they can cause serious diseases such as: 1 An infection in the blood 2 A lung infection (pneumonia) that can also come with an infection in the blood 3 An infection of the coverings of the brain and spinal cord (meningitis). PNEUMOVAX 23 may not protect everyone who gets it. It will not protect against diseases that are caused by bacteria types that are not in the vaccine. The most common side effects are: pain, warmth, soreness, redness, swelling, and hardening at the injection site headache weakness, feeling tired muscle pain Tell your health care provider or get emergency help right away if you have any of the following problems because these may be signs of an allergic reaction: difficulty breathing wheezing rash hives. hope this will help you regards