June 18 (Reuters) - Drugmaker Merck MRK.N said on Thursday the U.S. health regulator has approved an expanded use of its pneumococcal vaccine for children and teenagers who face a higher risk of catching the bacterial disease due to chronic health conditions.

Here are the details:

• The expanded approval covers patients aged 2 to 17 who have already completed a standard childhood pneumococcal vaccination schedule but have chronic conditions such as heart, lung, kidney, liver disease, or diabetes, which raise their risk of serious infections.

• The vaccine, branded as Capvaxive, is designed to protect against multiple strains of the Streptococcus pneumoniae bacteria.

• It was first approved by the U.S. Food and Drug Administration for adults in June 2024.

• Pneumococcal disease, caused by the bacteria, can lead to serious illnesses including pneumonia, meningitis, and blood infections.

• The disease spreads through contact with respiratory secretions such as saliva or mucus, and young children under five and adults 50 years and older are at higher risk of infection.

• Thursday's approval was based on results from a late-stage trial involving 874 participants, where the new vaccine matched or outperformed PPSV23, an older pneumococcal vaccine. Side effects were generally short-lived, Merck said.

• The vaccine is given as a single dose and is intended to complement existing childhood pneumococcal vaccines.