Two new studies undercut scientists hopes that people infected with the human immunodeficiency virus would be able to avoid having to take a drug "cocktail" of 20 to 30 pills a day for the rest of their lives, a regimen that can cost $15,000 a year and cause a variety of side effects. The studies published in The New England Journal of Medicine, found that attempts to reduce the number of medications had failed, allowing the resurgence of the virus.