Memory B cell responses induced by pneumococcal conjugate vaccine schedules with fewer doses: analysis of a randomised-controlled trial in Viet Nam.

The use of pneumococcal conjugate vaccine (PCV) schedules with fewer doses are being considered to reduce costs and improve access, particularly in low- and middle-income countries. While several studies have assessed their immunogenicity, there are limited data on their potential for long-term immune protection, as assessed by pneumococcal serotype-specific memory B cell (B_mem) responses. This current study reports secondary outcome data that aims to compare B_mem responses following reduced-dose (0 + 1 and 1 + 1) schedules of PCV10 and PCV13 in Vietnamese infants from our randomised-controlled trial (trial registration number NCT03098628). Following vaccination at 12 months of age, B_mem levels for most serotypes peaked seven days post-vaccination and were higher in magnitude for the 1 + 1 than 0 + 1 schedules and for PCV13 than PCV10. Furthermore, B_mem did not wane as rapidly as IgG levels by 24 months of age. Further studies are needed to assess the use of B_mem as markers of long-term protection against pneumococcal carriage and disease, which is crucial to generate data for immunisation program decision-making. As part of a randomized controlled trial in Viet Nam, this study finds that pneumococcal-specific memory B cells (B_mem) are higher following a 1 + 1 compared to a 0 + 1 pneumococcal conjugate vaccine (PCV) schedule and higher for PCV13 compared to PCV10. B_mem did not wane as rapidly as IgG by 24 months of age. [ABSTRACT FROM AUTHOR]