Perez Chacon G, Estcourt MJ, Totterdell J, et al. OPTIMUM study protocol: an adaptive randomised controlled trial of a mixed whole-cell/acellular pertussis vaccine schedule. BMJ Open 2020;10:e042838. doi: 10.1136/bmjopen-2020-042838

This article was previously published with an error.

Few errors on the visit schedule in figures 1 and 2 were fixed.

Below changes have been made in figure 1:

1. Visit 2: 4 to <5 months (instead of weeks)

2. Visit 3: 6 to <7 months (instead of weeks)

3. Visit 6: 12 to <18 months (instead of weeks)

4. Visit 7: 18 to <19 months (instead of weeks)

Below changes have been made in figure 2:

1. Visit 2: it is clarified that the vaccines will be given by a local immunisation provider

2. Visit 3: 18 to <19 months (instead of weeks)

3. OFC: ≥12 to <18 months (instead of >12)