[Antibody persistence following on different vaccination strategies of domestic measles, mumps and rubella combined attenuated live vaccine: a 3-year follow-up study].

Objective: To assess the 3-year antibody persistence after vaccination of domestic measles, mumps and rubella combined attenuated live vaccine (MMR) with different program. Methods: Children from three different vaccination strategies (Group 8 m MR: 8 months and 18 months vaccinated with measles-rubella combined attenuated live vaccine and domestic MMR,respectively; Group 8 m MMR: 8 months and 18 months both vaccinated with domestic MMR; Group 12 m MMR: 12 months and 22 months both vaccinated with domestic MMR ) were followed up in Zhejiang province in July 2015. There were 170 participants in Group 8 m MR, 171 participants in Group 8 m MMR and 173 participants in Group 12 m MMR selected by simple random sampling method .Blood samples (venous blood 2-3 ml) were collected 1 month after the first dose vaccination of MMR (only in Group 8 m MMR and Group 12 m MMR) and 3 years (36-38 months) after the last dose vaccination of MMR and tested for antibody IgG against Measles, Mumps and Rubella using ELISA. Seropostive rate and Geometric mean concentration (GMC) were calculated and compared among different groups by Chi-square test or Fisher exact test and Kruskal-Wallis H test. Results: A total of 514 participants (8 m MR: 170; 8 m MMR:171; 12 m MMR:173) were enrolled. The overall seropositivity rate of measles, mumps and rubella was 98.1% (504), 93.4% (480) and 88.1% (453), respectively, with corresponding GMC was 1 012.33 mU/ml, 502.87 U/ml and 50.53 U/ml respectively. There was no significant difference of seropositivity rate for measles among three groups (all groups were>97%). The highest seropositivity rate for mumps was found in the Group 12 m MMR with the rate of 98.8% (171/173), followed by Group 8 m MMR and Group 8 m MR with 93.0% (159/171) and 88.2%(150/170) respectively (Fisher exact test, P<0.001). The highest seropositivity rate for rubella was also found in the Group 12 m MMR with the rate of 94.8% (164/173), followed by Group 8 m MMR and Group 8 m MR with 86.6%(148/171) and 82.9%(141/170) respectively (Fisher exact test, P=0.002). The highest GMC of antibody against measles, mumps and rubella were all found in Group 12 m MMR, with 1 217.30 (1 119.35-1 323.82) mU/ml, 717.07 (643.83-798.65) U/ml and 62.54(56.21-69.58) U/ml respectively. The lowest GMC of antibody against measles and mumps were both in Group 12 m MR with 812.01 (734.52-897.67) mU/ml and 363.28 (305.42-432.11) U/ml respectively. The lowest GMC of antibody against rubella was in Group 8 m MMR with 44.10 (39.08-49.76) U/ml. These differences of GMCs among three groups were all reach significant means (P<0.05). Conclusion: High level seropostive rates and GMCs were exist against measles and rubella after 3-year vaccination of domestic MMR among different program. Higher antibody level against mumps were found in those children with two doses vaccination of MMR.