AIDS vaccine not as effective as first thought, scientists say

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Oct 22 2009

A vaccine to protect against HIV may not be as effective as first thought, scientists said Tuesday.

The Wall Street Journal: "When first publicly disclosing the outcome of the vaccine trial in September, researchers said the vaccine had lowered the risk of infection by about 31%. That result was modest but statistically significant." Two other analyses of the data have found, however, that the significance of the trials could be attributed to statistical chance. "Still, many scientists say the Thai experiment was useful because it was the first large-scale HIV-vaccine trial to yield a positive result" (Naik, 10/21).

The Los Angeles Times: "The key difference between the two types of analyses is that the original one excluded seven patients who were found to have HIV infections at the time the study began. The new analysis, based on what is called an intention-to-treat analysis, included all patients who were originally enrolled in the trial, producing the weaker results. Vaccine trials are typically analyzed both ways, and researchers expect to see statistically significant results from each analysis" (Maugh, 10/20).

The Washington Post reports that the results of the initial test were not statistically significant enough as defined by most medical research (Brown, 10/21).

The New York Times reports that the two analyses found the vaccine to be only 26 percent effective, lower than the 31 percent the initial trial had found— and that there was also a 16 percent probability that the results were due to chance. The clinical trial limit for the percentage that a result is due to chance is 5 percent (McNeil, 10/20).

Finally, The Senate passed a Ryan White CARE Act extension Monday that would allow more funding for a program that cares for people with HIV/AIDS, CQ reports (Ethridge and Nylen, 10/20). Open Congress has a summary of the bill.

This article was reprinted from khn.org with permission from the Henry J. Kaiser Family Foundation. Kaiser Health News, an editorially independent news service, is a program of the Kaiser Family Foundation, a nonpartisan health care policy research organization unaffiliated with Kaiser Permanente.