October 06, 2014
2 min read

Low vaccination rates, comorbidities risk factors for pH1N1-related pneumonia

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Low vaccination coverage and comorbidities such as diabetes and obesity appeared to be significant risk factors for influenza-related pneumonia in the 2013-2014 influenza season among adults in Mexico, according to recent findings.

Researchers from Hospital Central “Dr Ignacio Morones Prieto,” in San Luis Potosí, Mexico, characterized 102 patients admitted to the hospital with confirmed or suspected influenza pneumonia from Dec. 5, 2013, to Feb. 7, 2014. They compared these cases with 100 cases of confirmed influenza A(H1N1) pdm09 (pH1N1)infection reported in the 2009-2010 epidemic in Mexico.

The 102 patients hospitalized were aged 17 to 79 years and presented with acute cough or rhinorrhea with dyspnea, fever and radiographic signs of pneumonia. All patients provided blood samples, sputum samples or tracheal aspirates for influenza testing. The patients received empiric ceftriaxone with clarithromycin or levofloxacin, followed by a course of oseltamivir (Tamiflu, Genentech) within 6 hours of hospitalization.

The researchers identified pH1N1 in 47 patients and influenza A (no subtype identified) in eight patients. Among the 102 patients, the most common comorbidities were obesity (63 patients) and diabetes (23 patients). Only eight patients had received the influenza vaccine for the 2013-2014 season.

Most patients presented with severe illness and 52 patients required mechanical ventilation. Patients requiring mechanical ventilation were more likely to be obese: 76.5% were obese vs. 46.9% of those not requiring mechanical ventilation (P=.002). Patients requiring mechanical ventilation also had higher lactase dehydrogenase levels (406.8 mg/dL vs. 694.6 mg/dL; P=.006) and higher C-reactive protein levels (12.9 mg/dL vs. 19.7 mg/dL; P=.001).

Patients in the 2013-2014 wave of influenza were older (mean age, 46.1 years vs. 38.9 years; P<.001) and had a higher BMI (31.9 vs. 28.9; P<.001) compared with patients in the 2009-2010 pH1N1 outbreak. In addition, the 2013-2014 outbreak included a high number of severe cases among adults younger than 80 years.

According to the researchers, these findings indicate a need to alter the target population for influenza vaccination policies and to implement educational programs.

“To improve outcomes, additional measures could be implemented, such as campaigns and educational programs for the public and physicians that advocate early diagnosis, treatment, and identification of influenza-associated complications,” the researchers wrote. “In summary, to establish appropriate preventive measures, the epidemiologic characteristics of influenza outbreaks should be used to identify risk factors for severe infections.”

Disclosure: The researchers report no relevant financial disclosures.