Can we enter into Harvard Medical School without any 4 degree of undergraduate?

Answered

You can apply to Harvard with 3 years of undergraduate education but you must have a baccalaureate degree from an accredited university.

Plus you must complete their required course list prior to applying.

https://meded.hms.harvard.edu/admissions-prerequisite-courses

How this is usually accomplished is if you have taken 10-15 AP Classes in HS and say you got a score of 5 on 10 of them, Harvard will only give you college credit if you have a 5, not a 4. Or say you go to a near Ivy or elite college and they accept both 4s and 5s on APs and you can earn your BS degree in 3 years because the college credited you say 30-32 credits or units of coursework from your APs. Or you can just load up on college courses by taking an extra class each semester an attend 2 summer sessions and graduate 1 year early. You are not penalized for applying with 3 years of college but keep in mind that most applicants have an extra year or 2 extra years of education or life experience if they took a gap year prior to applying.

And if an applicant is from another country, they usually have "Supplemented their education with at least one year of college or university training in the United States or Canada if they have completed academic work outside the United States or Canada."

The acceptance rate is 3.3% and the avg. MCAT is 520/528 similar to Top 20 MD programs.

Hope that is helpful for you.