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The antineuraminidase activity of 5 inactivated split and subunit influenza vaccines (IIV) was studied in individuals aged above 65 years. Postvaccinal antibody titers were determined in the lectin test. All the vaccines were shown to have a high antigenicity, by providing high titers of neuraminidase antibodies in most vaccinated persons: The mean geometric titers (MGT) to influenza viruses A(H1N1) and A(H3N2), and B were 7.4-8.0, 8.5-9.2, and 6.8-8.5 log2, respectively. Neuraminidases showed a higher activity in Vaxigrip-vaccinated persons in terms of both the rate of MGT increases and seroconversion that was 78-84%. The parameters of the anti-neuraminidase (anti-NA) and anti-hemagglutinating (anti-HA) activities of IIV are summarized in the paper. There was a high coincidence of the results of both tests. At the same time it was shown that the postvaccinal humoral immune response might be directed only to one of the surface influenza virus proteins. The highest rate of seroconversions as to the surface antigens of all three influenza viruses was observed in Vaxigrip-vaccinated persons. The paper presents the results of comparison of the levels of MGT of antibodies to both viral surface proteins for all vaccinated with IIV, for those vaccinated who were infected during an epidemic season and a place group. The findings confirmed the value of higher titers of postvaccinal antibodies against influenza infection and illness.

A comparative study was carried out to assess reactogenicity and immunogenicity of inactivated influenza vaccines (Begrivac, Vaxigrip, Grippol, Influvac, and Fluarix), licensed in Russia. Immunization of the elderly demonstrated low reactogenicity and high immunogenicity for all vaccines. Concomitant chronic diseases had no influence on the vaccine immunogenicity levels, which testifies to the benefit of vaccination in this age group. In the group of vaccinated the highest seroconversion to all vaccine strains was found for Vaxigrip (82-89% for group A viruses and 86% for group B virus); the vaccine demonstrated the highest level of diagnostic increase of antibody titers to all 3 viruses, i.e. 69.0% (p < .05), with 22.0% of vaccinees gained antibodies to 2 vaccine viruses (91.0% in total). The number of positive responses to 3 and 2 strains in subjects immunized with Fluarix, Begrivac and Influvac reached 85.0%, 85.0% and 83.0% respectively. It is noteworthy that the combination of surface antigens of A and B flu viruses in low concentration with polyoxidonium immune modulator in Grippol induced intensive immune response.

To improve the vaccinal prophylaxis of influenza, the comparative study of live trivalent influenza allantoic vaccine, dried, for adults, produced by the Irkutsk Enterprise for Immunological Preparations (Russia), and inactivated trivalent influenza split vaccine, obtained from Wyeth-Ayerst Company (USA), as well as schedules of their combined use for the vaccination of elderly persons, was carried out. The examination of 600 subjects revealed that the vaccines were well tolerated; the combined use of these two vaccines, as well as the use of the inactivated influenza vaccine (IIV) alone, ensured high immunogenic activity (60.0-80.0% of seroconversions). The live influenza vaccine (LIV) stimulated the production of specific antibodies only in 19.0-35.0% of the vaccinees; most of these vaccinees exhibited positive reaction only to one of the vaccine strains. Following the injection of LIV, the level of postvaccinal immunity was retained for at least 6 months. In the vaccinees receiving both vaccines the tendency towards a decrease in mean geometric titer values was less pronounced (0.2-0.4 log2) than in those receiving only IIV (0.5-0.7 log2). At the period of the rise of influenza morbidity, the contamination rate in the vaccinees with the positive postvaccinal dynamics of antibodies was low (26.0%). The indices of effectiveness were 3.8 for combined vaccination, 3.5 for IIV and 2.6 for LIV. The schedule of vaccination with IIV with the possible revaccination LIV 3-4 weeks later was recommended.

During the epidemic season of 1989-1990 the subunit vaccine Grippovac was used in 20 asylums for old people and psychoneurological invalids in Moscow for the protection of the inhabitants and the personnel from influenza. Follow-up of the vaccinees during the period from November 1989 to March 1990 revealed that the use of this vaccine decreased the incidence of influenza-like diseases (ILD) 3.4-4.1 times among the vaccinees in comparison with that in the nonvaccinated control groups and significantly decreased the severity of the course of ILD, as well as the mortality because of ILD, among those vaccinees who had contacted ILD. This is indicative of good prospects of regular vaccinal prophylaxis of influenza at asylums for old people and other persons at a high risk of influenza complications.