The comparison of adverse reactions to anti-influenza vaccines of split-vision and surface antigens

Fear of adverse reactions is one of the reasons why influenza immunization programs for hospital workers have not met wide acceptance. We conducted a study in order to compare the frequency of adverse reactions following administration of standard split-virion (VVF) and subunit-virion (VAS) influenza vaccines, mostly among hospital personnel. Trial with volunteers who were systematically assigned to receive one of the vaccines, alternating every ten participants, during the influenza inmunization campaing 1994-95. The adverse effects were recorded by telephone interview 10 days after vaccination. Out the 182 subjects recruited, 163 were included in the study, of whom 100 received VAS and 63, VVF. Almost 13% of the participants reported any adverse effects with no significant difference between both groups (VAS: 11% and VVF: 15.6%, p = 0.38). There were also no significant differences relating to systemic and local reactions, separately. The subjects who had adverse reactions to previous influenza vaccination showed more frecuent systemic reactions (25% vs. 7.5%, p = 0.04) in a significant way. Both vaccines have been proved to be very safe, only causing adverse reactions in a small proportion and very mild in every case. The VAS presents a frequency of adverse effects similar to that of VVF, in spite of containing only surface antigens. It's likely that a certain hypersensitivity to influenza vaccine exists in some people, specially to the split-virion one.