Systemic and local antibody responses in elderly subjects given live or inactivated influenza A virus vaccines

Intranasal live attenuated cold-adapted (ca) influenza A/Kawasaki/9/86 (H1N1) reassortant virus and parenteral inactivated influenza A/Taiwan/1/86 (H1N1) virus were given alone or in combination to 80 ambulatory elderly subjects. An enzyme-linked immunosorbent assay was used to measure hemagglutinin-specific (HA) antibodies in serum and nasal wash specimens collected before vaccination and 1 and 3 months later. Serum immunoglobulin G (IgG) and nasal wash IgA HA responses were elicited in 56 and 20%, respectively, of 25 inactivated-virus vaccinees and in 67 and 48%, respectively, of 27 recipients of both vaccines but in only 36 and 25%, respectively, of 28 vaccinees given live virus alone. Inactivated virus, administered alone or with live virus vaccine, induced higher titers of serum antibody than did the live virus alone. In contrast, nasal IgA HA antibody was elicited more often and in greater quantity by the vaccine combination than by either vaccine alone. Despite these differences, the peak titers of local antibody mounted by each group of vaccinees were similar. By 3 months postvaccination, serum IgG and nasal IgA HA antibody titers remained elevated above prevaccination levels in 50 and 17%, respectively, of the inactivated-virus vaccinees and in 46 and 23%, respectively, of recipients of both vaccines but in only 19 and 7%, respectively, of the live-virus and systemic antibodies, if vaccinees. The finding that live ca influenza A virus induced short-lived local and systemic antibodies, if confirmed, suggests that live virus vaccination may not be a suitable alternative or adjunct to inactivated virus vaccination for the elderly.