Do Some Healthy Adults Consistently Have Systemic Reactions to Influenza Vaccines?

Randomized controlled trials of split virus vaccines in healthy adults have not been able to detect an increase in systemic adverse events compared to control vaccination. These trials do identify a non-trivial risk of systemic symptoms occurring in the week after both placebo and vaccine. There is a small population of healthcare workers who report consistent systemic symptoms after split virus vaccination which may occur because a small group of healthy adults have true physical reactions to components of the vaccine or excipients. If this is true, then alternatives - such as the use of subunit vaccines or live attenuated nasal spray vaccines - might be expected to be better tolerated by these people.

Inclusion criteria

• Employed or volunteer in a healthcare facility or an ambulatory care setting providing healthcare
• By self report, have had 2 or more doses of trivalent inactivated influenza vaccine (TIIV) in the last 15 years, and after at least the last 2 vaccine doses have had the same systemic adverse event in the 7 days after vaccination, including: fever, chills, myalgia, arthralgia, fatigue, headache, or insomnia;
• Consent to the study, including two injections one month apart, with one being placebo and one a dose of TIIV;

Exclusion criteria

• Has a contraindication to TIIV (previous allergic reaction to a dose of vaccine, or Guillain Barre syndrome with onset within 6 weeks of vaccination);
• Has previously received a dose of TIIV for the current influenza season.
• Receipt of another vaccine, or initiation of new medication within 7 days of the study injection (participant may enter the study as long as the gap between other vaccine/initiation of new medication is >7 days);
• Moderate or severe acute illness or active infection or fever (temperature ≥37.8oC) on the day a dose of study medication due (participant may receive injection 48 hours after symptoms have resolved and body temperature has returned to normal without the use of antipyretics.