Newborns develop a Th1-type immune response to Mycobacterium bovis Bacillus Calmette-Guerin vaccination

Data obtained in animals indicate that neonatal immune responses are biased toward Th2. This could reduce the efficacy of vaccines against viral and m ycobacterial diseases. The ability of human newborns to develop a Th1 immun e response upon immunization has not been studied. Since the vaccine Mycoba cterium bovis bacillus Calmette-Guerin (BCG) triggers a Th1-type response i n adults, we investigated whether it induces a similar response in newborns and whether age at vaccination influences immunogenicity. We found that BC G vaccination at birth induces a memory Th1-type response of similar magnit ude to that when given later in life. This study demonstrates that human ne wborns can be immunized against pathogens controlled by a Th1 immune respon se.