Immunogenicity and safety of subunit influenza vaccines in pregnant women

Pregnancy is a condition of modulated immune suppression, so this group of patients has increased risk of infectious diseases. Trivalent subunit vaccines, unadjusted Agrippal S1 (group I) and immunoadjuvant Grippol Plus (group II), containing 5 μg of actual influenza virus strains, were administered respectively to 37 and 42 women in the second and third trimester of physiological pregnancy. The administration of subunit influenza vaccines was accompanied by the development of local reactions in no more than 10% of patients, compared with 4.9% of the 41 pregnant women in the placebo group (group III). Systemic reactions were of a general somatic nature, did not differ between vaccinated and placebo groups, and were not associated with vaccination. Physiological births in groups I, II and III were 94.6%, 92.9% and 85.4%, respectively, and the birth rates of children without pathologies were 91.9%, 90.5% and 80.5%, respectively, and were comparable between groups. Vaccination stimulated the production of protective antibodies against influenza virus strains in 64.8–94.5% of patients after immunisation with an unadjusted vaccine and in 72.5–90.0% of patients after the administration of an immunoadjuvant vaccine. After 9 months, antibody levels were recorded in 51.3–72.9% in group I and 54.2–74.2% in group II. Immunisation against influenza in pregnant women provided a high level of seroprotection and seroconversion. Nevertheless, the level of seroprotection against the influenza strain A(H3N2, Victoria) was slightly lower in the group immunised with an unadjusted vaccine compared to those vaccinated with the immunoadjuvant vaccine.