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. 2023 May 11;41(20):3292-3300.
doi: 10.1016/j.vaccine.2023.03.069. Epub 2023 Apr 5.

Vaccine effectiveness against transmission of alpha, delta and omicron SARS-COV-2-infection, Belgian contact tracing, 2021-2022

Toon Braeye  1 , Lucy Catteau  2 , Ruben Brondeel  2 , Joris A F van Loenhout  2 , Kristiaan Proesmans  2 , Laura Cornelissen  2 , Herman Van Oyen  3 , Veerle Stouten  2 , Pierre Hubin  2 , Matthieu Billuart  2 , Achille Djiena  4 , Romain Mahieu  5 , Naima Hammami  6 , Dieter Van Cauteren  2 , Chloé Wyndham-Thomas  2
Affiliations

Vaccine effectiveness against transmission of alpha, delta and omicron SARS-COV-2-infection, Belgian contact tracing, 2021-2022

Toon Braeye et al. Vaccine. .

Abstract

Objectives: Vaccine effectiveness against transmission (VET) of SARS-CoV-2-infection can be estimated from secondary attack rates observed during contact tracing. We estimated VET, the vaccine-effect on infectiousness of the index case and susceptibility of the high-risk exposure contact (HREC).

Methods: We fitted RT-PCR-test results from HREC to immunity status (vaccine schedule, prior infection, time since last immunity-conferring event), age, sex, calendar week of sampling, household, background positivity rate and dominant VOC using a multilevel Bayesian regression-model. We included Belgian data collected between January 2021 and January 2022.

Results: For primary BNT162b2-vaccination we estimated initial VET at 96% (95%CI 95-97) against Alpha, 87% (95%CI 84-88) against Delta and 31% (95%CI 25-37) against Omicron. Initial VET of booster-vaccination (mRNA primary and booster-vaccination) was 87% (95%CI 86-89) against Delta and 68% (95%CI 65-70) against Omicron. The VET-estimate against Delta and Omicron decreased to 71% (95%CI 64-78) and 55% (95%CI 46-62) respectively, 150-200 days after booster-vaccination. Hybrid immunity, defined as vaccination and documented prior infection, was associated with durable and higher or comparable (by number of antigen exposures) protection against transmission.

Conclusions: While we observed VOC-specific immune-escape, especially by Omicron, and waning over time since immunization, vaccination remained associated with a reduced risk of SARS-CoV-2-transmission.

Keywords: Alpha Variant of Concern; Delta Variant of Concern; Infection-acquired immunity; Infectiousness; Omicron Variant of Concern; SARS-CoV-2; Susceptibility; Transmission; Vaccine Effectiveness; Vaccine-induced immunity; Viral-vector vaccine; mRNA-vaccine.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Initial, 0–50 days after vaccination, effectiveness VEs (susceptibility, upper) and VEi (infectiousness, lower) by VOC by vaccine and prior infection, females, 45–64 years, Belgian contact tracing, 26/01/2021 – 10/01/2022.
Fig. 2
Fig. 2
VET-estimates for females aged 45–64 years old without prior infection by VOC (upper = Delta, lower = Omicron) and time since vaccination (left = 0–50 days, right = 150–200 days). Belgian contact tracing, 26/01/2021 – 10/01/2022. The first column presents VE-estimates against susceptibility (protection of the HREC by vaccination against exposure from an unvaccinated index case), the lowest row presents VE-estimates against infectiousness (protection of unvaccinated HREC through reduced infectiousness of an index case by vaccination).
Fig. 3
Fig. 3
VET-estimates against Omicron over time since vaccination/prior infection by immunity status (mRNA + Booster without and with prior infection, BNT162b2 primary-vaccination and infection-acquired immunity without vaccination), females 45–64 years, Belgian contact tracing, 26/01/2021 – 10/01/2022.
See this image and copyright information in PMC

References

    1. Proesmans K, Hancart S, Braeye T, Klamer S, Robesyn E, Djiena A, et al. COVID-19 contact tracing in Belgium: main indicators and performance, January – September 2021. Arch Public Health. 2022 Apr 13;80(1):118. - PMC - PubMed
    1. Braeye T., Cornelissen L., Catteau L., Haarhuis F., Proesmans K., De Ridder K., et al. Vaccine effectiveness against infection and onwards transmission of COVID-19: Analysis of Belgian contact tracing data, January-June 2021. Vaccine. 2021 Sep 15;39(39):5456–5460. - PMC - PubMed
    1. Braeye T, Catteau L, Brondeel R, van Loenhout J, Proesmans K, Cornelissen L, et al. VACCINE EFFECTIVENESS AGAINST ONWARD TRANSMISSION OF SARS-COV2-INFECTION BY VARIANT OF CONCERN AND TIME SINCE VACCINATION, BELGIAN CONTACT TRACING, 2021. Vaccine [Internet]. 2022 Apr 12 [cited 2022 Apr 17]; Available from: https://www.sciencedirect.com/science/article/pii/S0264410X22004418. - PMC - PubMed
    1. de Gier B., Andeweg S., Joosten R., ter Schegget R., Smorenburg N., van de Kassteele J., et al. Vaccine effectiveness against SARS-CoV-2 transmission and infections among household and other close contacts of confirmed cases, the Netherlands, February to May 2021. Eurosurveillance. 2021 Aug 5;26(31):2100640. - PMC - PubMed
    1. Eyre D.W., Taylor D., Purver M., Chapman D., Fowler T., Pouwels K.B., et al. Effect of Covid-19 Vaccination on Transmission of Alpha and Delta Variants. N Engl J Med. 2022 Feb 24;386(8):744–756. - PMC - PubMed

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