The dengue fever vaccine disaster on the Philippines is another good example why one should be cautious. Dengue fever is the canonical example of antibody-depen

The dengue fever vaccine disaster on the Philippines is another good example why one should be cautious. Dengue fever is the canonical example of antibody-dependent enhancement - someone who has antibodies against a certain strain of dengue fever will show a very serious reaction when he is infected with a different strain of the virus. That's why people who are given the dengue vaccine must have been infected with dengue previously. On the Philippines, they gave the dengue vaccine to schoolchildren, a substantial number of whom were seronegative. The disease in that population was much more serious than it would have been otherwise, there were unnecessary deaths, and a good number of parents avoided the measles vaccine for their children, and a measles outbreak promptly followed.