An MF59-adjuvanted inactivated influenza vaccine containing A/Panama/1999 (H3N2) induced broader serological protection against heterovariant influenza virus strain A/Fujian/2002 than a subunit and a split influenza vaccine

To test whether inactivated influenza vaccines distributed during the 2003–2004 influenza season in the northern hemisphere were able to confer protection against the mismatched variant A/Fujian/411/2002 virus strain, we measured haemagglutination inhibiting (HI) antibodies in elderly subjects vaccinated with three inactivated vaccines against the homologous A/H3N2 vaccine strain (A/Panama) and against the mismatched A/Fujian strain. The results showed that, while 76 to 80% of elder people vaccinated with conventional vaccines had protected levels of antibodies against the A/Fujian heterovariant strain, those vaccinated with the MF59-adjuvanted vaccine have protective levels of antibodies in >98% of the cases. We conclude that MF59-adjuvanted vaccines confer protection also against influenza virus strains which are not fully matched with those included in the vaccine.