Background:
In Italy Rotavirus vaccination (RVV) is recommended and provided free of charge from 2018, however, the coverage is scattered and suboptimal. The narrow time frame to complete the schedule is a major barrier to vaccine uptake, and co-administration with other vaccines may potentially increase the coverage. Although the co-administration of RVV and Meningococcal Group B vaccines (MenB) is currently not included into product labels, we aimed at studying its impact on RVV coverage.

Methods:
The Regional Vaccination Registry was used to conduct a retrospective cohort study in children born in Campania Region between January 1, 2016 and December 31, 2020, and receiving vaccines scheduled in the first year of life.

Results:
A total of 224.110 children accessing the vaccination centers in the study period were included. Overall 60.614 (27.0%) completed the RVV schedule, with a progressive increase over time (from 1.15% in 2016 to 56.92% in 2020), in parallel with MenB/RVV co-administration (from 0.7% in 2016 to 46.85% in 2020). Monovalent RVV schedule (2-doses) was completed in 91.1% of children compared to pentavalent RVV Schedule (3-doses) in 81.3% (p<0.00001). Children receiving RVV/MenB co-administration had a significant higher chance to complete RV schedule compared to those receiving RVV alone during a specific appointment (94.78% vs 72.26%, Prevalence Ratio -PR- 1.275, 95%IC 1.245-1.295 p<0.00001). The positive effect of RVV/MenB co-administration was more evident for children receiving pentavalent RVV (PR 1.288) than monovalent RVV (PR 1.115), this evidence was confirmed when adjusted for confounding variables (i.e.year of vaccination, local health district, gender).

Conclusion:
Although still far from the target, the RVV coverage has increased in recent years in Campania Region. Co-administration with MenB vaccine may aid in achieving this goal, especially for Rotateq. More data about safety and tolerability are needed to support co-administration as a key tool to increase coverage.