Adults 50 and older can now get the shot, as rates of the illness climb.

The Centers for Disease Control and Prevention has lowered the recommended age from 65 to 50 for adults to get vaccinated against a type of bacteria that causes pneumonia and other illnesses.

The shots protect against a cluster of infections known as pneumococcal disease, including a common form of pneumonia; sinus, ear and blood infections; and meningitis, all caused by Streptococcus pneumoniae bacteria.

These infections tend to be both more common and more severe in older adults, said Dr. Benjamin Singer, a pulmonary and critical care specialist at Northwestern Medicine Canning Thoracic Institute. And cases have been rising in the years since coronavirus lockdowns slowed disease transmission, including an increase among people between the ages of 50 and 64.

“I’ve been hoping for this for some time,” Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center, said about the change.

The C.D.C. announced the new guideline on Wednesday. The agency also recommends vaccinating children under 5, as well as people who are at increased risk because of conditions like diabetes; chronic heart, liver or kidney disease; or other underlying issues that weaken the immune system.

As of 2022, only around 24 percent of adults had reported ever getting a pneumococcal vaccine, according to the C.D.C. Doctors have long observed stark racial disparities in who pneumococcal disease hits the hardest: Black adults get sick with diseases like pneumonia at disproportionately higher rates. The lowered age recommendation may encourage more people to get the shots.

“The idea is if we can vaccinate more people fairly and equitably, that we will reduce the morbidity and mortality disparity,” said Dr. Geeta Sood, an assistant professor at the Johns Hopkins School of Medicine.

The guideline comes as particularly welcome news to doctors who are dreading the winter virus season. Contracting other viral infections, like the flu or respiratory syncytial virus (better known as R.S.V.), can make someone more susceptible to pneumococcal disease. And patients are often stunned by just how serious a case of pneumonia can be, Dr. Sood said.

“People do get a lot more sick from it than you would think,” she said. “Even healthy-ish adults who I’ve known who have gotten pneumococcal pneumonia — they will feel not quite themselves and yucky for weeks on end. It’s not a nothing disease.”

If you’re not sure whether you’ve been vaccinated, talk to your doctor, Dr. Sood suggested. (The Times also has tips for checking your immunization records.) People who receive these vaccines have reported mild side effects: fatigue, fever, chills, head and muscle aches, and tenderness around the injection site. Most adults need only one dose of the pneumococcal vaccine to be protected for life.

“We live in a very fortunate time, where we have really effective vaccines to help prevent very severe disease,” Dr. Sood said.