Abstract

Postpartum women may have an altered susceptibility to Plasmodium falciparum and Plasmodium vivax. The relationship between naturally acquired malarial immunity and susceptibility to malaria postpartum is yet to be determined. IgG levels were measured against P. falciparum and P. vivax antigens from delivery in 201 postpartum and 201 nonpregnant controls over 12 weeks. Associations between time‐varying antibody levels and time to first microscopically confirmed species‐specific infection were determined by Cox regression. Associations between antibody levels and prospective risk of Plasmodium infection were similar in postpartum and control women. A 2‐fold increase in P. falciparum antibody levels was associated with increased prospective risk of P. falciparum infection (hazard ratio [HR] range = 1.37–1.94). Antibody levels against most P. vivax antigens displayed no association with prospective risk of P. vivax infection (HR range = 1.02–1.05) with the exception of PvMSP119 antibodies that were weakly associated with prospective risk of P. vivax infection (HR = 1.14 (95% confidence interval = 1.02, 1.28) per 2‐fold increase in levels). Associations between antibody levels and prospective risk of infection attenuated when adjusted for documented retrospective exposure. Serology may be a useful tool to predict and monitor women at increased risk of P. falciparum infection postpartum, particularly in the absence of a detailed history of retrospective infections.

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This work was supported by the National Health and Medical Research Council ofAustralia (project grant and training award to Freya J. I. Fowkes; Infrastructure for Research InstitutesSupport Scheme grant), Australian Research Council (Future Fellowship to Freya J. I. Fowkes), andVictorian State Government Operational Infrastructure Support grant to the Burnet Institute. Alistair R.D. McLean is supported by an Australian Postgraduate Award. Shoklo Malaria Research Unit is part ofthe Mahidol Oxford University Tropical Medicine Research Unit supported by the Wellcome Trust ofGreat Britain. The Christophe and Rodolphe Mérieux Foundation supported the study through a prize(2008) to François Nosten.