Hybrid immunity and protection against infection during the Omicron wave in Malta

By December 2021, administration of the third dose of COVID-19 vaccinations coincided with the spread of the Omicron variant in Europe. Questions had been raised on protection against infection conferred by previous vaccination and/or infection. Our study population included 252,433 participants fro...

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Main Authors: John Paul Cauchi, Ausra Dziugyte, Maria-Louise Borg, Tanya Melillo, Graziella Zahra, Christopher Barbara, Jorgen Souness, Steve Agius, Neville Calleja, Charmaine Gauci, Pauline Vassallo, Joaquin Baruch
Format: Article
Language:English
Published: Taylor & Francis Group 2023-12-01
Series:Emerging Microbes and Infections
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Online Access:https://www.tandfonline.com/doi/10.1080/22221751.2022.2156814
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author John Paul Cauchi
Ausra Dziugyte
Maria-Louise Borg
Tanya Melillo
Graziella Zahra
Christopher Barbara
Jorgen Souness
Steve Agius
Neville Calleja
Charmaine Gauci
Pauline Vassallo
Joaquin Baruch
author_facet John Paul Cauchi
Ausra Dziugyte
Maria-Louise Borg
Tanya Melillo
Graziella Zahra
Christopher Barbara
Jorgen Souness
Steve Agius
Neville Calleja
Charmaine Gauci
Pauline Vassallo
Joaquin Baruch
author_sort John Paul Cauchi
collection DOAJ
description By December 2021, administration of the third dose of COVID-19 vaccinations coincided with the spread of the Omicron variant in Europe. Questions had been raised on protection against infection conferred by previous vaccination and/or infection. Our study population included 252,433 participants from the COVID-19 vaccination registry in Malta. Data were then matched with the national testing database. We collected vaccination status, vaccine brand, vaccination date, infection history, and age. Using logistic regression, we examined different combinations of vaccine dose, prior infection status and time, and the odds of infection during the period when the Omicron variant was the dominant variant in Malta. Participants infected with Sars-Cov-2 prior to the Omicron wave had a significantly lower odds of being infected with the Omicron variant. Additionally, the more recent the infection and the more recent the vaccination, the lower the odds of infection. Receiving a third dose within 20 weeks of the start of the Omicron wave in Malta offered similar odds of infection as receiving a second dose within the same period. Time since vaccination was a strong determinant against infection, as was previous infection status and the number of doses taken. This finding reinforces the importance of future booster dose provision especially to vulnerable populations.
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issn 2222-1751
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spelling doaj-art-307199a71a074e28be8df4dffcc96d3d2025-08-20T03:52:57ZengTaylor & Francis GroupEmerging Microbes and Infections2222-17512023-12-0112110.1080/22221751.2022.2156814Hybrid immunity and protection against infection during the Omicron wave in MaltaJohn Paul Cauchi0Ausra Dziugyte1Maria-Louise Borg2Tanya Melillo3Graziella Zahra4Christopher Barbara5Jorgen Souness6Steve Agius7Neville Calleja8Charmaine Gauci9Pauline Vassallo10Joaquin Baruch11Infectious Disease Prevention and Control Unit (IDCU), Health Promotion and Disease Prevention, Msida, MaltaInfectious Disease Prevention and Control Unit (IDCU), Health Promotion and Disease Prevention, Msida, MaltaInfectious Disease Prevention and Control Unit (IDCU), Health Promotion and Disease Prevention, Msida, MaltaInfectious Disease Prevention and Control Unit (IDCU), Health Promotion and Disease Prevention, Msida, MaltaMolecular Diagnostics Pathology Department, Mater Dei Hospital, Msida, MaltaMolecular Diagnostics Pathology Department, Mater Dei Hospital, Msida, MaltaMater Dei Hospital, Msida, MaltaMater Dei Hospital, Msida, MaltaHealth Information and Research, Msida, MaltaMinistry for Health, Superintendent of Public Health, Msida, MaltaInfectious Disease Prevention and Control Unit (IDCU), Health Promotion and Disease Prevention, Msida, MaltaInfectious Disease Prevention and Control Unit (IDCU), Health Promotion and Disease Prevention, Msida, MaltaBy December 2021, administration of the third dose of COVID-19 vaccinations coincided with the spread of the Omicron variant in Europe. Questions had been raised on protection against infection conferred by previous vaccination and/or infection. Our study population included 252,433 participants from the COVID-19 vaccination registry in Malta. Data were then matched with the national testing database. We collected vaccination status, vaccine brand, vaccination date, infection history, and age. Using logistic regression, we examined different combinations of vaccine dose, prior infection status and time, and the odds of infection during the period when the Omicron variant was the dominant variant in Malta. Participants infected with Sars-Cov-2 prior to the Omicron wave had a significantly lower odds of being infected with the Omicron variant. Additionally, the more recent the infection and the more recent the vaccination, the lower the odds of infection. Receiving a third dose within 20 weeks of the start of the Omicron wave in Malta offered similar odds of infection as receiving a second dose within the same period. Time since vaccination was a strong determinant against infection, as was previous infection status and the number of doses taken. This finding reinforces the importance of future booster dose provision especially to vulnerable populations.https://www.tandfonline.com/doi/10.1080/22221751.2022.2156814COVID-19vaccineshybrid immunitypublic healthomicron (B.1.1.529)
spellingShingle John Paul Cauchi
Ausra Dziugyte
Maria-Louise Borg
Tanya Melillo
Graziella Zahra
Christopher Barbara
Jorgen Souness
Steve Agius
Neville Calleja
Charmaine Gauci
Pauline Vassallo
Joaquin Baruch
Hybrid immunity and protection against infection during the Omicron wave in Malta
Emerging Microbes and Infections
COVID-19
vaccines
hybrid immunity
public health
omicron (B.1.1.529)
title Hybrid immunity and protection against infection during the Omicron wave in Malta
title_full Hybrid immunity and protection against infection during the Omicron wave in Malta
title_fullStr Hybrid immunity and protection against infection during the Omicron wave in Malta
title_full_unstemmed Hybrid immunity and protection against infection during the Omicron wave in Malta
title_short Hybrid immunity and protection against infection during the Omicron wave in Malta
title_sort hybrid immunity and protection against infection during the omicron wave in malta
topic COVID-19
vaccines
hybrid immunity
public health
omicron (B.1.1.529)
url https://www.tandfonline.com/doi/10.1080/22221751.2022.2156814
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