SAN DIEGO, CA—Researchers reported a “low to moderate” influenza vaccine effectiveness for preventing influenza admissions during the northern hemisphere’s 2013/2014 flu season.

“While influenza vaccination is to be recommended for preventing influenza-related disease, improved vaccines that offer better protection are needed,” concluded lead study author Joan Puig-Barbera, MD, MPH, PhD, from Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO) in Valencia, Spain.

The researchers conducted a multicentric study through the Global Influenza Hospital Surveillance Network (GIHSN). They prospectively screened influenza-like illness (ILI) admissions from December 2013–June 2014 for influenza viruses in 19 hospitals across Russia, Turkey, China, and Spain to estimate influenza vaccine effectiveness (IVE).

Among a total of 4,660 eligible admissions, 1,108 (22%) were influenza test-positive patients with 13% vaccinated, and 3,642 (78%) were test-negative controls with 20% vaccinated, Dr. Puig-Barbera reported.

“Influenza A(H3N2) virus comprised 50% of the test-positive specimens,” she noted. A(H1N1)pdm09 virus was present in 33% and B/Yamagata-lineage virus was present in 12% of test-positive specimens.

The coauthors noted moderate vaccine protection overall, with adjusted efficacy against laboratory-confirmed hospitalizations for influenza A(H3N2), A(H1N1)pdm09 and A(H1N1) B/Yamagata lineage viruses of 28% (95% CI: -6 to 51), 38% (95% CI: 15 to 55), and 61% (95% CI: -5 to 86), respectively.

IVE estimates were significantly larger in the elderly population (49%; 95% CI: 22 to 77) than in younger patients (22%; 95% CI: -26 to 52; P=0.02), Dr. Puig-Barbera noted. Heterogeneity by geographic site was not statistically significant.