Serum antibodies against circulating influenza strains among vaccinated and unvaccinated general practitioners during two consecutive years (2002–2003)

Efficacy studies have not answered the question whether influenza vaccination among general practitioners (GPs) has a substantial additive effect on their immunity. To evaluate this effect the influenza antibody titres in vaccinated and unvaccinated GPs were compared in a controlled trial during two consecutive winter periods (2002–2003 and 2003–2004). The seroprotection rates against the circulating A/H3N2 influenza virus amount to 80% and 42% in the unvaccinated group in 2002 and 2003, respectively. In the vaccinated GPs the seroprotection rate increases from 91% to 96% in 2002 and from 70% to 83% in 2003 after vaccination. Besides vaccination, the (high) basic antibody titre before vaccination and working in a child and family preventive medicine unit were predicting a protective antibody level in GPs.