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. 2023 Apr 3;76(7):1180-1187.
doi: 10.1093/cid/ciac914.

Impact of Vaccination With the SCB-2019 Coronavirus Disease 2019 Vaccine on Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 Infection: A Household Contact Study in the Philippines

Birkneh Tilahun Tadesse  1   2   3 , Lulu Bravo  4 , Florian Marks  1   5   6   7 , Asma Binte Aziz  1 , Young Ae You  1 , Jonathan Sugimoto  8   9   10 , Ping Li  11 , Joyce Garcia  11 , Frank Rockhold  12 , Ralf Clemens  1 ; Household Contact Study Group
Collaborators, Affiliations

Impact of Vaccination With the SCB-2019 Coronavirus Disease 2019 Vaccine on Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 Infection: A Household Contact Study in the Philippines

Birkneh Tilahun Tadesse et al. Clin Infect Dis. .

Abstract

Background: An exploratory household transmission study was nested in SPECTRA, the phase 2/3 efficacy study of the adjuvanted recombinant protein-based COVID-19 vaccine SCB-2019. We compared the occurrence of confirmed COVID-19 infections between households and household contacts of infected SPECTRA placebo or SCB-2019 recipients.

Methods: SPECTRA participants at 8 study sites in the Philippines who developed real-time reverse transcriptase-polymerase chain reaction (rRT-PCR)-confirmed COVID-19 were contacted by a study team blinded to assignment of index cases to vaccine or placebo groups to enroll in this household transmission study. Enrolled households and household contacts were monitored for 3 weeks using rRT-PCR and anti-SARS-CoV-2 N-antigen IgG/IgM testing to detect new COVID-19 infections.

Results: One hundred fifty-four eligible COVID-19 index cases (51 vaccinees, 103 placebo) were included. The secondary attack rate per household for symptomatic COVID-19 infection was 0.76% (90% CI: .15-3.90%) if the index case was an SCB-2019 vaccinee compared with 5.88% (90% CI: 3.20-10.8%) for placebo index cases, a relative risk reduction (RRR) of 79% (90% CI: -28% to 97%). The RRR of symptomatic COVID-19 per household member was similar: 84% (90% CI: 28-97%). The impact on attack rates in household members if index cases were symptomatic (n = 130; RRR = 80%; 90% CI: 7-96%) or asymptomatic (n = 24; RRR = 100%; 90% CI: -76% to 100%) was measurable but the low numbers undermine the clinical significance.

Conclusions: In this prospective household contact study vaccination with SCB-2019 reduced SARS-CoV-2 transmission compared with placebo in households and in household members independently of whether or not index cases were symptomatic.

Trial registration: ClinicalTrials.gov NCT04672395.

Keywords: COVID-19; SARS-CoV-2; SCB-2019; household transmission; vaccination.

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Conflict of interest statement

Potential conflicts of interest. P. L. and J. G. are full-time employees of the study sponsor, Clover Biopharmaceuticals, and receive an employment total award package as well as salary. R. C. reports participation as Chair Scientific Advisory Board for Clover Biopharmaceuticals, plays a role on the Board for Clover Biopharmaceuticals and the Board of Trustees for the International Vaccine Institute (IVI), and has stock or stock options in Clover Biopharmaceuticals. J. S. reports consulting fees from IVI and participation on a Data Safety and Monitoring Board (DSMB) for the OPTIMMS Trial (Oxford University, Andrew Pollard as Principal Investigator). F. R. reports personal fees from Clover Biopharmaceuticals during the conduct of the study, personal fees from Merck Research Labs, personal fees from Novartis, personal fees from Lilly, grants and personal fees from AstraZeneca, personal fees from Union Chimique Belge, personal fees from Sanofi, personal fees from Amgen, personal fees from Icosavax, personal fees from Gilead, grants from Eidos, grants from Bristol Myers Squibb, personal fees from Janssen, personal fees from Doctor Evidence, grants from American Regent, personal fees from Biogen, personal fees from Intercept, personal fees from Alkermes, and personal fees from Diurnal, outside the submitted work, and equity interest in GSK, Athira, Spencer Healthcare, Clover Biopharmaceuticals, Doctor Evidence, Odyssey Topco, and Adaptic Health. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Disposition of households, HHCs, and household infections by vaccinated/placebo index case (SPECTRA). Abbreviations: COVID-19, coronavirus disease 2019; HHC, household contact(s).
See this image and copyright information in PMC

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