Re-recruiting postpartum women living with HIV into a follow-up study in Cape Town, South Africa.

Using telephone calls, home visits, clinic tracing and Facebook/WhatsApp messages, we located 387 of the 463 eligible women and successfully enrolled 353 (91% of those contacted). Phone calls were the most successful strategy, yielding 67% of enrolments. Over half of the women had changed their contact information since participation in the previous study. We recommend that researchers collect multiple contact details and use several recruitment strategies in parallel from the start of a study. Participants in longitudinal studies may require frequent contact to update contact information, particularly in settings where mobility is common.