although 96 % of infants who received a full dose were able to mount a serologic response to pertussis after a second dose of dtp , 45 % of infants who received a half dose were unable to mount a similar immune response to pertussis even after a third dose of dtp and required a full-dose ( fourth dose of dtp ) vaccine to better ensure protection .
C0043167
dtp
C0031237
dtp