Immunity response against mild-to-moderate breakthrough COVID-19

  1. Pichanun Mongkolsucharitkul
  2. Apinya Surawit
  3. Nitat Sookrung
  4. Anchalee Tungtrongchitr
  5. Pochamana Phisalprapa
  6. Naruemit Sayabovorn
  7. Weerachai Srivanichakorn
  8. Chaiwat Washirasaksiri
  9. Chonticha Auesomwang
  10. Tullaya Sitasuwan
  11. Thanet Chaisathaphol
  12. Rungsima Tinmanee
  13. Methee Chayakulkeeree
  14. Pakpoom Phoompoung
  15. Watip Tangjittipokin
  16. Sansanee Senawong
  17. Gornmigar Sanpawitayakul
  18. Saipin Muangman
  19. Korapat Mayurasakorn
  20. the SPHERE Investigators
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Abstract

BACKGROUND

The Omicron variant prevails the Delta variant after December 2021 in Thailand. Both variants of concern embody diverse epidemiological trends and immunogenicity, raising enormous public health concerns. We determined whether biological and clinical characteristics and immunogenicity of patients differ between Delta and Omicron during post-coronavirus disease 2019 (COVID-19) stage.

METHODS

A retrospective cohort study involved patients with mild-to-moderate COVID-19 who were under a home isolation (HI) strategy. Clinical outcomes and laboratory data of 2704 and 2477 patients during the Delta and Omicron pandemics were analyzed, respectively. We evaluated anti-receptor binding domain immunoglobulin G (anti-RBD IgG) and surrogate viral neutralizing (sVNT) activity in a subset of 495 individuals post-COVID-19 infection during the Delta pandemic.

RESULTS

Eighty-four percent of all patients received antiviral treatment. The peak cycle threshold (Ct) values, which inversely related to viral load, were lower in the Omicron (19 [IQR=17-22]) compared with the Delta (21 [IQR=18-26]; p<0.001), regardless of vaccination status. Upper respiratory tract symptoms were common signs during the Omicron compared with the Delta pandemic. At least two-dose vaccination reduced the chance of hospital readmissions by 10–30% and death by less than 1%. Furthermore, anti-RBD IgG and sVNT against the Delta variants tended to be higher among the older individuals after post-COVID 19 infections and expressed in the long interval after two-dose vaccination than in other groups.

CONCLUSIONS

Mild-to-moderate Delta and Omicron breakthrough infection with prior full vaccination is limitedly immunogenic; thereby exerting reduced protection against reinfection and infection from novel variants. However, this may be only sufficient to prevent hospitalization and death, particularly in countries where vaccines are limited. ( <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://ClinicalTrials.gov">ClinicalTrials.gov</ext-link> number, <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="clintrialgov" xlink:href="NCT05328479">NCT05328479</ext-link> .)

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