A randomized trial of two acellular pertussis vaccines (dTpa and pa) and alicensed diphtheria-tetanus vaccine (Td) in adults

A single blinded randomized controlled trial to compare the reactogenicity and immunogenicity of adult formulated dTpa and monovalent pa vaccines with a licensed Td vaccine. Five hundred and forty-eight healthy adults aged 19 -70 years received a single injection of dTpa or separate injections of pa or Td (with the alternate vaccine month later). Local and systemic reaction s were monitored for 15 days after each vaccination. Serum antibody levels were measured immediately prior to and 1 month after vaccination. Antibody levels were measured 12 months after vaccination in 100 subjects. There was no difference in the total Frequency of symptoms and signs between subject s receiving any of the three vaccines. There was a significantly lower inci dence of local reactions following pa (60%) than dTpa (80%, P = 0.002) or T d (93% P = 0.0008). The incidence of clinically significant (Grade 2 or 3) swelling (greater than or equal to 20 mm) was higher for Td (20%, P = 0.002 ) than for dTpa (11%) or for pa (2%), however, there were no other signific ant differences in the incidence of Grade 2 or 3 reactions between the vacc ines. A high anti-pertussis seroconversion rate ( > 97%) against all the st udied pertussis antigens was seen month after vaccination with dTpa and pa. PI total of 96 and 99% of subjects receiving dTpa and Td, respectively, ha d anti-diphtheria titres greater than or equal to 0.01 IU/ml, and all but o ne subject had anti-tetanus titres greater than or equal to0.1 IU/ml after 1 month. Twelve months after vaccination the majority (90- 100%) of the sub jects were still seropositive for each antigen and although GMTs had decrea sed they were substantially higher than pre-vaccination levels. The dTpa va ccine was well tolerated and capable of eliciting an immune response agains t all the antigens in a broad spectrum of the adult population and could po tentially replace Td for routine boosters in adults. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.