This study evaluated the antibody persistence of Chinese children five years after they received four doses of sIPV, two doses of MMR vaccine and one dose of HepA-L vaccine.

This is a follow-up study of several previous clinical trials (A Randomized, Controlled, Multicenter Phase 4 Clinic Trial to Evaluate the Immunogenicity and Safety of Combined Immunization of Sabin-strain Inactivated Polio Vaccine (sIPV), Diphtheria, Tetanus, Pertussis Vaccine (DTaP) and Measles, Moms and Rubella Vaccine (MMR) : NCT04054882, NCT04638985; A Randomized, Controlled, Multicenter Phase 4 Clinic Trial to Evaluate the Safety and Immunogenicity of Combined Immunization of Sabin-strain Inactivated Polio Vaccine (sIPV), Diphtheria, Tetanus, Pertussis (DTaP) Vaccine and Live Attenuated Hepatitis A Vaccine (HepA): NCT04053010, NCT04636827). Five years after vaccination with sIPV, MMR or HepA-L, blood samples were collected from the followed-up children to assess the antibody levels and seropositive rates against polio, measles, rubella, mumps and hepatitis A. This study was conducted in six provinces of China.

Inclusion Criteria:

• Participants in the NCT04638985 or NCT04636827, and who have completed the vaccination of designated batch numbers of sIPV, MMR or HepA-L vaccines;
• The time window from the day of enrollment to the date when the participants received the fourth dose of sIPV vaccine, the second dose of MMR vaccine, or the first dose of HepA-L vaccine was 60 to 66 months.
• The informed consent form shall be signed by the participant or his/her legal guardian and dated.

Exclusion Criteria:

• None.

Participants who have taken part in the NCT04638985 or NCT04636827 trials and have completed the designated batches of sIPV, MMR or HepA-L vaccinations, with a time interval of 60 to 66 months since the fourth dose of sIPV, the second dose of MMR or the first dose of HepA-L vaccination at the time of enrollment.