Covid 19 Boosters ???

Cuba has some pretty high standards of medical care and doctors and scientists. This vaccine seems to have a high efficacy rate, much higher than the Chinese vaxes Mexico seemed to be mostly offering. WHO approval isn't something I'd care about- the scientific studies and peer reviews are more important to me.
https://www.thelancet.com/journals/lanam/article/PIIS2667-193X(22)00183-1/fulltext

Do you mean whether they are allowing people to get them only if they haven't had an original vaccine, rather than letting people get them as boosters?

There is no difference between a shot you get as the first and second dose and what is given as a booster. Except of course if it's a different brand or is the beefed up bivalent vaccines that were developed to work better for Omicron.