Debate on annual influenza vaccination in healthcare workers for the same subtype under the vaccine shortage

BackgroundInfluenza vaccination is the primary method for preventing influenza and its severe complications. Healthcare workers (HCWs) are one of the priority groups for the influenza vaccination.ObjectivesTo determine whether healthy HCWs, who were vaccinated with the same subtype for the two previous years, could be given less priority for influenza immunization under the vaccine shortage.Study designWe measured hemagglutination-inhibition antibody titers from sequential serum samples in 50 pre-immune subjects and 50 age-matched vaccine-naive subjects: immediately prior to the administration of the vaccine, 4–6 weeks, and 6 months after the vaccination.ResultsPrevaccination titers were maintained above protective level and high protection rates were observed for all three strains in pre-immune subjects: A/H1N1, A/H3N2, and B strains. As for the sequential changes, the protection rates for all three strains still remained above 70% until 6 months following the vaccination.ConclusionSkipping influenza vaccination for a year could be considered in healthy pre-immune HCWs under the epidemic of the same subtype as two previous years.