The Effect of Concurrent Tetanus-diphtheria Vaccination on the Antibody Response to Rabies Vaccine: A Preliminary Study

The number of studies in the literature investigating the effect of tetanus vaccination on rabies prophylaxis is rather limited. In this study, we aimed to investigate the effect of concurrent tetanus-diphtheria (Td) vaccination on the antibody response to rabies vaccine. The data of consecutive 80 patients who presented to Sakarya University Training and Research Hospital, Department of Emergency due to rabies suspected exposure between 15 October 2012 and 12 June 2013 were enrolled to this study. Postexposure rabies prophylaxis had been given to all cases, however concurrent tetanus vaccination had been administered to some of them according to their need. Cases were divided into two parts according to their receipt of tetanus prophylaxis as rabies only group (group R, n=37), and rabies and tetanus-diphtheria group (group R+Td, n=43). Rabies antibody levels were tested in sera of the cases at first and postvaccination 21st day. The median antibody levels of each group were measured and compared with each other statistically. In our study, postvaccination 21st day antibody level of group R was 0.68 IU/ml (IQR: 0.79), while the same for group R+Td was 0.52 IU/ml (IQR: 0.48) (p=0.022). Concurrent administration of Td vaccine was found to have a significant negative effect on the antibody response to rabies vaccine. Our results should be confirmed with further studies including more cases.