Sometimes infectious diseases can be passed on by adults who haven't gotten recommended booster shots, such as for whooping cough.

WSJ: Where Could The Next Outbreak Of Measles Be?

The researchers will look to see if their immune systems respond to the booster shots in the same way that those of the rhesus macaque monkeys did.

FORBES: Merck, Aventis Team On AIDS Vaccine

Merck and Aventis will immediately start giving booster shots based on Aventis' current version of the canarypox vaccine to 90 or more patients who have already participated in a test of Merck's adenovirus vaccine.

FORBES: Merck, Aventis Team On AIDS Vaccine