Recent epidemiological events showed that pregnant women are the most vulnerable part of population if there is the flu in the country and they die much more often than the rest part of people. That is why influenza vaccination of population including pregnant women is one of the priorities of public health service in our state. Worldwide experience of influenza vaccination of either adults or children by new adjuvant vaccine has caused our research of its efficiency among pregnant women. The aim of the study was to investigate the level of antibodies to influenza virus strain A/H1N1/v, A/H3N2 and B in pregnant women vaccinated adjuvant trivalent subunit vaccine. Our research is randomized and comparative on parallel groups. It was carried out within the demands of Russian Federation and International ethic norms adapted to such kind of researches. Evaluation of the immunogenicity of the vaccine was conducted in 27 pregnant women in the II trimester of gestation, and in 23 pregnant women in the III trimester of gestation, 19 non-pregnant women was in the control group. The level of antibodies in the serum was determined using a reaction of hemagglutination inhibition before and 1, 3, 6, 9 and 12 months after the vaccination. Revealed that influenza vaccination of pregnant women in the II and III trimester, causes the increase in titers of antibodies to vaccine influenza strains A and B, to fully meet the required criteria CPMP, and does not differ from the nonpregnant group. In a month after vaccination the level of seroprotective against A/H1N1/v was 77.0%, A/H3N2 — 88.9%, B — 85.2% after vaccination in II trimester, and 87.0; 87.0; 91.35% in III trimester of gestation. The factor of seroconversion after vaccination in II trimester for A/H1N1/v was equal to 6.5, A/H3N2 — 7.2, B — 6.5, after vaccination in III trimester of pregnancy: 7.1, 6.5 and 5.1 correspondingly. At the same time revealed accelerated decline in antibody titer against influenza in pregnant women compared to nonpregnant women in a year after immunization The set of results of the study can be concluded that adjuvant trivalent subunit vaccine effective in vaccination of pregnant women in II and III trimester of pregnancy, and it is able to effectively provide immune protection against viruses of the flu A and B within all pregnancy long.