Comparison of Adverse Reactions to Split-Virion and Subunit-Virion Influenza Vaccines

Abstract

Background: 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. Methods: Trial with volunteers who were systematically assigned to receive one of the vaccines, altemating every ten participants. during the influenza inmunization campaing 1994-95. The adverse effects were recorded by telephone interview 10 days after vaccination. Results: 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=O.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=O.O4) in a significant way. Conclusions: Both vaccines have been proved to be verysafe, only causing adverse reactions in a rmall 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 certein hypersensitivity to inlluenza vaccine exists in some people, specially to the spit-virion one.