More than 80% of ear infections can resolve on their own. Sometimes antibiotic treatment is necessary, especially if there is no improvement with a few days of watching an otherwise healthy child and providing pain relief with acetaminophen or ibuprofen. Infants younger than 6 months with an infection, however, should receive antibiotics without delay. Some children with special circumstances should be more aggressively treated. These conditions include congenital heart disease, cleft palate, Down syndrome, or immune system problems (such as leukemia, other cancers, or inherited disorders of the immune system). Children who have an episode of acute otitis media within 30 days of another episode usually require antibiotic treatment. Ear tubes are not the first-line treatment for acute otitis media, though they may be offered to individuals who have chronic middle ear fluid or chronic otitis media. Children with repeated ear infections are often referred to an otolaryngologist (a doctor with specialized education in the management and surgery of head and neck problems) for evaluation. Ongoing research may offer new recommendations for treatment of acute otitis media. Since the vaccine for Streptoccocus pneumoniae (PCV) was introduced, other bacteria not covered by this vaccine are now more common causes of acute otitis media. Antibiotic resistance (when bacteria are no longer killed by certain antibiotics) also changes with time, and this may influence the choice of antibiotic treatment in the future.