Low birthweight and prematurity, but not malaria chemoprevention, are associated with reduced pneumococcal vaccine immunogenicity in Ugandan infants.

BACKGROUND

Malaria exposure has been hypothesized to alter immune responses to childhood vaccines, but evidence is inconsistent. We evaluated whether early-life malaria exposure and perennial malaria chemoprevention (PMC) modify antibody responses to the 10-valent pneumococcal conjugate vaccine (PCV-10) among infants in a high malaria transmission setting in eastern Uganda.

METHODS

This study was nested within the MIC-DroP trial (NCT04978272) whereby 202 infants were selected for inclusion. Serotype-specific IgG concentrations were measured using an in-house multiplex seroassay from samples obtained at 8 and 24 weeks of age. Immunogenicity was quantified as the log10 fold-change in IgG concentration between the 8 and 24-week timepoints, and seroconversion as ≥0.35 μg/mL at week 24 (i.e., seropositive). Generalized estimating equation models were used to assess associations of PCV-10 immunogenicity and seroconversion with malaria exposure, malaria chemoprevention and birth outcomes.

RESULTS

Among the 195 of 202 infants who completed the three-dose PCV-10 series, neither infant PMC nor malaria exposure from study enrollment to 14 weeks were associated with PCV-10 immunogenicity or seroconversion. In contrast, low birthweight (<2500g) was associated with lower immunogenicity (82% lower antibody fold-change, p=0.003) and reduced odds of seroconversion (OR=0.19, p=0.003); preterm birth (<37 weeks) showed similar associations (79% lower antibody fold-change, p=0.018; OR=0.181, p=0.009).

CONCLUSION

In this malaria-endemic setting, early-life malaria exposure and chemoprevention did not measurably alter PCV-10 antibody responses. However, low birthweight and prematurity were associated with reduced vaccine immunogenicity.