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While influenza immunization significantly reduces the risk of pneumonia and associated deaths, vaccination of elderly only affords 30-50% protection against influenza disease. The purpose of this study was to: (1) evaluate the consistency of immune responses across multiple years in young and elderly; (2) determine the contribution of antibody and cell-mediated responses in protection after immunization with influenza vaccine. Independently living healthy elderly (>200/year; mean age 78.8-80.6/year) were recruited yearly in this four year study. The results clearly demonstrate: (1) both young and elderly consistently produced significant antibody and T cell proliferative responses to influenza vaccine upon yearly immunization; however, both responses of elderly were significantly and consistently lower than young. (2) Percentages of both young and elderly demonstrating protective titers (i.e. HI>/=40) increased post-immunization each year, but were consistently higher in young compared to elderly. (3) The risk of developing influenza disease after immunization was highest among elderly demonstrating neither antibody nor cell-mediated responses. Importantly, the risk of influenza disease was comparable in elderly demonstrating a cell-mediated response alone, an antibody response alone, or both cell-mediated and antibody responses. This suggests that cell-mediated responses play a significant role in protection in at least a subset of elderly from influenza disease after immunization.

The effects of yearly influenza immunization on the level of antibody responses were assessed in 92 healthy elderly subjects immunized over four contiguous years (1993-1996) with a trivalent influenza vaccine that included A/Texas annually. Anti-A/Texas antibodies increased significantly and similarly post-vaccination each year, but returned to comparable baseline levels annually. Percentages of subjects with anti-A/Texas titers > or =40 post-vaccination were comparable over four years. Importantly, post-vaccination titers > or =40 to A/Texas in 1993-1994 predicted anti-A/Texas titers > or =40 in subsequent years. Thirty percent of individuals produced four-fold rises to any vaccine component the first year it was included in the vaccine, however, this percentage decreased to about 10% after subsequent vaccination with the same component. This study clearly supports the concept that annual immunization with the same influenza vaccine component over multiple years does not significantly decrease antibody titers in a healthy elderly population.

Background: repeated influenza immunization does not appear to adversely affect the serum antibody response to new influenza strains., Objective: to determine whether the immune response to a new influenza strain was inferior in persons previously vaccinated compared with persons not previously vaccinated., Design: randomized, double-blind clinical trial., Setting: university affiliated community teaching hospital., Patients: 139 healthy adult men and women, mean age 38 years., Intervention: subjects were vaccinated as part of another study. They received influenza vaccines containing influenza strains A/Texas/36/91 (H1N1), A/Nanchang/933/95 (H3N2) and B/Beijing/184/93. One group received a licensed influenza vaccine while the other group received a similar vaccine except the A/Nanchang strain had a diminished potency., Measurements: serum hemagglutination inhibition (HAI) antibody titers were determined prior to vaccination and two weeks afterward. If patients had a low postvaccination titer, they were revaccinated and HAI titers were determined two weeks later., Results: 68 adults received the licensed vaccine and 70 received the subpotent vaccine. The groups were similar with regards to baseline characteristics. Those previously vaccinated had significantly lower postvaccination HAI geometric mean titers (GMTs) for all three vaccine strains (A/Texas--127 vs. 359, p < 0.001, A/Nanchang--31 vs. 93, p < 0.001 and B/Beijing--140 vs. 205, p < 0.05). The percentage of subjects with a presumed protective HAI titer of > or =40 was significantly lower among the previously vaccinated groups only for the new influenza strain, A/Nanchang (55% vs. 80%, p < 0.05). For the other two vaccine strains, the percentage with an HAI titer > or =40 was greater than 90% for both groups., Conclusions: the decrease in serologic response to influenza vaccine among healthy, young adults who were previously vaccinated appears to be unique for this year's influenza vaccine. Further studies are required to determine the frequency and clinical significance of this phenomenon observed in younger healthy adults, and whether it is a general one. Based on its proven efficacy, influenza vaccine should continue to be given on an annual basis to high risk children and adults and to all those 65 years or older.

The earliest time at which serum antibody levels peak following administration of an influenza virus vaccine in elderly persons is not clearly defined. We compared the time intervals of 1 and 2 weeks after vaccination. A commercial trivalent vaccine containing the hemagglutinins of influenza viruses A/Texas/36/91 (H1N1), A/Johannesburg/33/94 (H3N2), and B/Harbin/7/94 was used. The hemagglutination inhibition (HAI) antibody titers at 1 week after vaccination were significantly lower than the HAI titers at 2 weeks postvaccination for all three vaccine components.

Objective: To determine the effect of repeated annual influenza immunization on the host's serum antibody., Design: Ten year observational study with cohort design., Setting: Cystic Fibrosis Center at St. Vincent's Hospital and Medical Center, New York City, NY., Patients: Thirty-eight children and young adults with cystic fibrosis (CF)., Measurements: Serum hemagglutination inhibition (HI) antibody titers were determined at the time of vaccination and 4 weeks later each year in the fall before the influenza epidemic. Shwachman scores were determined each year., Results: While the pre-vaccination and post-vaccination geometric mean serum HI antibody titers varied from year to year, no upward or downward trend was evident over the 10 year period. The reciprocal of the post-vaccination geometric mean HI titers ranged annually from 32 to 74 for the influenza A (H3N2) vaccine strains, from 53 to 133 for the influenza A (H1N1) strains, and from 18 to 174 for influenza B strains. In addition, the majority of vaccinees had a presumably protective post-vaccination serum HI titer > or = 1:40 each year for all three vaccine strains. The initial mean Shwachman score of the group was 77. The final score of 76 after 10 years was not significantly different., Conclusions: Annual influenza vaccination appears to regularly induce presumably protective serum antibody levels in most CF children and young adults studied over a 10 year period.

The earliest time at which serum antibody peaks following administration of influenza virus vaccine in elderly persons is not clearly defined. We compared the time intervals of 2 and 4 weeks after vaccination. A commercial trivalent vaccine containing the hemagglutinins of influenza viruses A/Texas/36/91(H1N1), A/Shangdong/9/93(H3N2), and B/Panama/45/90 was used. The hemagglutination inhibition antibody titers at 2 weeks after vaccination were identical to the hemagglutination inhibition antibody titers at 4 weeks for all three vaccine components.

The time to the appearance of a peak serum antibody response to influenza virus vaccine is not clearly defined. We compared the most commonly used time intervals described in the literature--4 and 6 weeks after vaccination. We studied 118 elderly patients from three different geographic sites. The 1992 to 1993 trivalent inactivated influenza virus vaccine containing influenza virus A/Beijing/353/89 (H3N2), influenza virus A/Texas/36/91 (H1N1), and influenza virus B/Panama/45/90 was used. No statistically significant differences were found at the 4- and 6-week intervals after vaccination.

The purpose of this study was to determine whether acetaminophen impairs the immune response to influenza vaccine. Influenza vaccine is an under-utilized preventive measure, partly because of the unfounded perception that fever and myalgias frequently follow vaccination. While acetaminophen may decrease these infrequent side effects, it may also alter the immune response to vaccination. We compare the effect of acetaminophen with placebo on the humoral immune response to the 1991-1992 commercially available influenza vaccine. We studied 60 healthy, elderly subjects from a geriatric clinic and 20 infirm, elderly subjects from a nursing home. The subjects were randomly assigned to receive placebo or acetaminophen (1,000 mg every 6 h) for 2 days. Acetaminophen did not depress or enhance the immune development of serum hemagglutination inhibition antibody to the three vaccine antigens. The systemic side effects of fever and myalgia were uncommon in both groups. The healthy elderly subjects mounted a significantly better immune response to the influenza virus A/Taiwan/1/86 (H1N1) vaccine strain than did the infirm elderly subjects (geometric mean titer, 115 versus 51; P = 0.003). The functional activity score obtained by using the chronic healthy evaluation component of the Acute Physiology and Chronic Health Evaluation system could be used to distinguish the healthy from the infirm elderly (scores of 1.27 versus 3.75, P < 0.001). Acetaminophen neither depressed nor enhanced the serum antibody response to the vaccine in the healthy and infirm elderly subjects studied.