The CDC says:
If soap and water are unavailable, use an alcohol-based hand sanitizer that contains at least 60% alcohol to clean hands.
But then this 2005 publication says:
Alcohol-based hand sanitizers, which do not require water, are a boon for harried parents and busy caregivers in hospitals and other institutions. They rapidly kill most bacteria and viruses, and products that contain emollients tend to be gentler on the hands than soap and water. An increasing body of literature suggests that regular use of alcohol-based hand sanitizers can reduce transmission of infections in hospitals and other health care settings…
Wikipedia cites various studies of efficacy, including:
Mackintosh (1984) found that application of 0.3 milliliters alcohol rub to the hands was no more effective than plain soap-and-water hand washing, but that increasing the volume to 0.5 milliliters increased the effectiveness of alcohols substantially.[32] In environments with high lipids or protein waste (such as food processing), the use of alcohol hand rubs alone may not be sufficient to ensure proper hand hygiene).[31]
They also list some infectious agents that are resistant to alcohol. The same article also compares alcohol to antiseptic soap:
Alcohol based hand rubs provide a better skin tolerance as compared to antiseptic soap.[11] Hand rubs also prove to have more effective microbiological properties as compared to antiseptic soaps.
I work in a hospital environment where hand sanitizers are mounted on practically every wall. I use it maybe 50 times a day but still wash my hands at a sink several times a day.