Common vaccines that require 3 doses include recombinant New Coronavirus Vaccine, New Coronavirus Inactivated Vaccine Booster, Hepatitis B Vaccine, and HPV Vaccine, etc. Because the types are different, the intervals between the 3 doses are also different. 1. Recombinant New Coronavirus Vaccine: 3 doses are required, and the interval between the 2 adjacent doses should be at least 4 weeks. The 2nd dose should be completed as close as possible to 8 weeks after the 1st dose, and the 3rd dose should be completed as close as possible to 6 months after the 1st dose. 2. New Crown inactivated vaccine booster: Two doses of basic immunization, with a recommended interval of ≥3 weeks between doses, with the second dose completed as early as possible within 8 weeks. The third booster vaccination should be given 6 months after the completion of the second vaccination to those aged 18 years and above. 3. Hepatitis B Vaccine: Hepatitis B vaccination requires a 1-month interval between the 1st dose of Hepatitis B vaccine and the 2nd dose. The 3rd vaccination is then given 6 months after the 1st vaccination. 4. HPV Vaccine: HPV vaccine is usually given at intervals of 0, 2 and 6. That is, the 2nd injection is given 2 months after the 1st injection, and the 3rd injection is given when you reach 6 months. In addition to this there are other types of vaccines that require 3 injections. For the specific vaccination schedule, it is recommended that you consult your local CDC department, and if you need to be vaccinated, you should choose a regular vaccination institution for the vaccination.