According to JV Chamary, PhD, in a July 2020 Forbes article
The CDC's recommendation to use hand sanitizer with at least 60% ethanol is wrong with reference to Coronavirus, and its guidelines need updating.
[...]
At concentration of 60%, ethanol might work against germs generally, but not coronaviruses specifically. Studies showed that 80% is effective against enveloped viruses within 30 seconds, which means that at lower concentrations (such as 43%) it will take longer — maybe a minute, by which time the alcohol might have evaporated from the skin before it could have the desired effect. People tend to squirt a few drops of sanitizer into the palm of one hand then rub their hands together for a few seconds, and 60% ethanol wouldn't be effective enough over that time scale.
Contrary to these claims, other sources ague that "more is not better" when it comes to the amount of alcohol in hand sanitizer:
For example, an April 2020 article on MarthaStewart.com argues that
70% Isopropyl Alcohol Is a Better Disinfectant Than 99% Isopropyl Alcohol When It Comes to COVID-19
Is the US CDC recommending the wrong strength of hand sanitizer to kill the SARS-CoV-2 virus that causes COVID-19?
A related question asks about even lower percentages of alcohol.
