Serious pH1N1 Influenza Illness and Pneumonia Despite Inactivated Vaccine: Success of Prompt Diagnosis and Treatment

A 42-year-old bedridden patient suddenly became seriously ill with an unexplained fever (39°C) and hypoxemia (pulse oximetry oxygen saturation: patient, 90%; normal, >98%). He had received the inactivated vaccine for pandemic 2009 H1N1-influenza (pH1N1) 41 days earlier. He had no cough, sore throat, or pharyngitis. Therefore, he did not satisfy the Centers for Disease Control criteria for an “influenza-like illness.” Nevertheless, his nasopharyngeal swab was tested by rapid enzyme-linked immunosorbent assay for influenza A and found positive. He was promptly treated with supplemental oxygen and oseltamivir (75 mg twice daily) for 5 days. On day 6, reverse transcriptase-polymerase chain reaction test confirmed the virus to be pH1N1. A chest radiograph was normal on day 1 but revealed bilobar pneumonia on day 2. This was considered bacterial superinfection and empirically treated for 10 days with 3 g of piperacillin and 375 mg of tazobactam. The patient fully recovered. This case of pH 1N1 vaccine failure occurred because no vaccine is 100% protective, and immune response may be poorer in patients with chronic medical problems. Vaccine failure was not due to immunodeficiency or improper vaccine handling. We credit this patient's recovery to our facility's heightened surveillance for influenza even among the vaccinated individuals, and also in those without classic influenza-like illness.