As variable as flu is, HIV makes flu look like the Rock of Gibraltar. The virus that causes AIDS is the trickiest pathogen scientists have ever confronted.

The return on investment in global health is tremendous, and the biggest bang for the buck comes from vaccines. Vaccines are among the most successful and cost-effective health investments in history.

Investments in immunization yield a rate of return on a par with educating our children - and higher than nearly any other development intervention.

The best vaccine imaginable is only valuable to the extent we get it to everyone who needs it.

For just a few dollars a dose, vaccines save lives and help reduce poverty. Unlike medical treatment, they provide a lifetime of protection from deadly and debilitating disease. They are safe and effective. They cut healthcare and treatment costs, reduce the number of hospital visits and ensure healthier children, families and communities.

Healthy children are more likely to attend school and are better able to learn. Healthy workers are more productive. More productive economies mean greater stability in developing countries and improved security in the West.

As many times as [HIV] changes its clothes, it's still wearing the same socks, and now our job is to make sure we get the body to really hate those socks.