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. 2023 Jun 28:14:1190093.
doi: 10.3389/fimmu.2023.1190093. eCollection 2023.

Durability and extent of protection of SARS-CoV-2 antibodies among patients with COVID-19 in Metro Manila, Philippines

Ma Liza Antoinette M Gonzales  1 , Leonila F Dans  1   2 , Carol Stephanie C Tan-Lim  2 , Elenore Uy  3 , Eva Cutiongco-Dela Paz  4 , Maria Vanessa V Sulit  5 , Marissa M Alejandria  2 , Mary Ann D Lansang  2 , Antonio L Dans  6 , Melissa A Dator  1 , Cynthia P Cordero  2 , Gina F Pardilla  7
Affiliations

Durability and extent of protection of SARS-CoV-2 antibodies among patients with COVID-19 in Metro Manila, Philippines

Ma Liza Antoinette M Gonzales et al. Front Immunol. .

Abstract

Introduction: Information on the magnitude and durability of humoral immunity against COVID-19 among specific populations can guide policies on vaccination, return from isolation and physical distancing measures. The study determined the durability of SARS-CoV-2 antibodies after an initial infection among Filipinos in Metro Manila, Philippines, and the extent of protection SARS-CoV-2 antibodies confer against reinfection.

Methods: We conducted a cohort study to monitor the antibody levels of patients diagnosed with COVID-19. Receptor-binding domain (RBD)-specific antibodies were measured at Days 21, 90, 180, 270 and 360. Antibody levels were reported as geometric mean titers (GMT) with geometric standard deviation (GSD). Differences in GMT were tested using Friedman test and Kruskal Wallis test, with Bonferroni multiple comparisons procedure. Adjusted hazard ratios on the development of probable reinfection were estimated using Cox proportional models.

Results: There were 307 study participants included in the study, with 13 dropouts. Study participants received SARS-CoV-2 vaccines at varying times, with 278 participants (90.5%) fully vaccinated by the end of study. The GMT of the study cohort increased over time, from 19.7 U/mL (GSD 11) at Day 21; to 284.5 U/mL (GSD 9.6) at Day 90; 1,061 U/mL (GSD 5.3) at Day 180; 2,003 U/mL (GSD 6.7) at Day 270; and 8,403 U/mL (GSD 3.1) at Day 360. The increase was statistically significant from Day 21 to Day 90 (p<0.0001), Day 90 to Day 180 (p=0.0005), and Day 270 to Day 360 (p<0.0001). Participants with more severe initial infection demonstrated significantly higher antibody levels compared to those with milder infection at Day 21. Sixty-four patients had probable COVID-19 reinfection (incidence of 20.8%, 95% CI 16.4, 25.8%). The GMT of these 64 patients was 411.8 U/mL (GSD 6.9) prior to the occurrence of the probable reinfection. Majority (87.5%) were fully vaccinated. Antibody titers significantly affected the risk of developing reinfection, with adjusted hazard ratio of 0.994, 95% CI 0.992-0.996, p<0.001.

Conclusion: Antibody levels against SARS-CoV-2 increased over a one-year follow-up. Higher antibody levels were observed among those with more severe initial infection and those vaccinated. Higher antibody levels are associated with a lower risk of probable reinfection.

Keywords: COVID-19; SARS-CoV-2; antibody; humoral response; reinfection.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Epidemiological context in the Philippines and the timing of study implementation. (Image modified from the https://doh.gov.ph/covid19tracker)[12]. BE1 = first blood extraction at day 21, BE2 = second blood extraction at day 90, BE3 = third blood extraction at day 180, BE4 = fourth blood extraction at day 270, BE5 = fifth blood extraction at day 360.
Figure 2
Figure 2
Flowchart of screening, enrollment and monitoring procedures.
Figure 3
Figure 3
Geometric mean titers of SARS-CoV-2 antibodies (U/mL) of all study participants across the 5 timepoints *p=<0.0001, **p=0.0005.
Figure 4
Figure 4
Geometric mean titers of SARS-CoV-2 antibodies (U/mL) according to initial COVID-19 disease severity classification.
Figure 5
Figure 5
Geometric mean titers of SARS-CoV-2 antibody levels (U/mL) according to vaccination status at the end of the study. *Day 90 - 5 dropouts (n=14); Day 180 - 1 dropout and 1 missed blood extraction (n=12); Day 270 - 1 missed blood extraction (n=12); Day 360 - 1 dropout and 1 missed blood extraction (n=11). **Day 90 - 13 partially vaccinated and 13 fully vaccinated; Day 180 - 13 partially vaccinated and 54 fully vaccinated, 2 dropouts and 1 missed blood extraction (n=73); Day 270 – 68 fully vaccinated, 2 dropouts and 3 missed blood extractions (n=69); Day 360 – 66 fully vaccinated, 2 dropouts and 4 missed blood extractions (n=66). ***Day 90 – 104 partially vaccinated and 47 fully vaccinated, 1 missed blood extraction (n=211); Day 180 – 9 partially vaccinated, 202 fully vaccinated (n=212); Day 270 – 1 partially vaccinated, 155 fully vaccinated, 56 with booster; Day 360 – 212 with booster.
See this image and copyright information in PMC

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Supplementary concepts