Table 3. Change in antibody levels following homologous and heterologous infection.
| Regression coefficient (95% confidence interval); p value |
||||||
|---|---|---|---|---|---|---|
|
P. falciparum infection during follow-upa |
P. vivax infection during follow-upa |
|||||
| All women | Postpartumb | Controlsb | All women | Postpartumb | Controlsb | |
| Pfmerozoite (log2(OD)) | 0.85 (0.57, 1.13); <0.001 | 0.65 (0.23, 1.06); 0.002 | 1.02 (0.65, 1.40); <0.001 | — | — | — |
| PfCSP (log2(OD)) | 0.36 (0.18, 0.54); <0.001 | 0.42 (0.09, 0.75); 0.01 | 0.52 (0.28, 0.76); <0.001 | 0.14 (0.03, 0.25); 0.01 | 0.10 (−0.04, 0.24); 0.17 | 0.20 (0.04, 0.36); 0.01 |
| PfDBLα (log2(OD)) | 0.18 (0.01, 0.35); 0.03 | 0.20 (−0.05, 0.45); 0.12 | 0.17 (−0.06, 0.40); 0.14 | — | — | — |
| PfVAR2CSA (log2(MFI)) | −0.01 (−0.19, 0.16); 0.89 | −0.02 (−0.28, 0.25); 0.90 | −0.01 (−0.24, 0.23); 0.94 | — | — | — |
| Pvmerozoite (log2(OD)) | — | — | — | 0.35 (0.19, 0.50); <0.001 | 0.30 (0.10, 0.51); 0.004 | 0.40 (0.17, 0.64); 0.001 |
| PvCSP (log2(OD)) | 0.34 (0.11, 0.57); 0.004 | 0.18 (−0.16, 0.52); 0.30 | 0.47 (0.17, 0.77); 0.002 | 0.18 (0.04, 0.31); 0.01 | 0.14 (−0.5, 0.32); 0.15 | 0.23 (0.02, 0.44); 0.03 |
Estimates of regression coefficient (95% CI) and p-value derived from linear mixed-effects modelling are presented. Models were adjusted for postpartum, clinic attended, history of working outdoors, age (except PfVAR2CSA), gravidity >2 (for PfVAR2CSA only) and time (weeks). The effect of heterologous species infection was assessed for each antibody response but only incorporated into the final model if there was evidence against a null effect (p < 0.05).
aInfection during follow-up was included as a time-varying variable with presence of infection (yes or no) at any visit prior to the corresponding antibody level measurements.
bPostpartum interaction with infection during follow-up was tested using the likelihood ratio test (comparing models with and without the interaction terms) to assess if the response to infection was modified by postpartum status. For Pfmerozoite, p = 0.19; PfCSP, p = 0.09; PfDBLα, p = 0.89; PfVAR2CSA, p = 0.97; Pvmerozoite, p = 0.53; PvCSP, p = 0.35.