The tetanus-diphtheria-acellular pertussis vaccine was comparable in safety and efficacy with tetanus and diphtheria vaccine in patients ages 65 and older, according to a study published online in the journal Clinical Infectious Diseases. Tdap vaccine users showed no increased risk of adverse reactions including meningitis and encephalitis compared with Td users. Seniors who received the Tdap vaccine, however, were nearly four times more likely to develop generalized reaction and anaphylaxis and were more likely to need medical attention for allergic or inflammatory reactions within six days of vaccination.