Protection of vaccination versus hybrid immunity against infection with COVID-19 Omicron variants among Health-Care Workers. Issue 50 (28th November 2022)

• Record Type: Journal Article
• Authors: Ntziora, Fotinie; Kostaki, Evangelia Georgia; Karapanou, Amalia; Mylona, Maria; Tseti, Ioulia; Sipsas, Nikolaos V.; Paraskevis, Dimitrios; Sfikakis, Petros P.
• Is Part Of: Vaccine. Volume 40:Issue 50(2022)
• Page Start: 7195
• Page End: 7200
• Publication Date: 2022-11-28
• Subjects: COVID-19 -- Vaccine -- Infection rate -- Hybrid immunity -- Health-Care Workers (HCWs); ACE2 Angiotensin-converting enzyme 2 -- CDC Centers for Disease Control and Prevention -- CI Confidence Interval -- COVID-19 Coronavirus Disease 2019 -- HCWs Health-Care Workers -- IDSA Infectious Diseases Society of America -- IQR interquartile range -- PCR Polymerase Chain Reaction -- RBD Receptor-Binding Domain -- SARS-CoV-2 Severe Acute Respiratory Syndrome Coronavirus 2 -- VOCs Variants of Concern; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2022.09.042
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: Hybrid and vaccination-induced immunity conferred protection against severe Omicron infection. Compared to vaccination alone hybrid immunity protected for Omicron infection by almost 5-fold. Omicron strain lead to COVID-19 in almost half of the participants, despite vaccination. Abstract: Background aim: The Omicron COVID-19 variants BA.1* and BA.2* evade immune system leading to increased transmissibility and breakthrough infections. We aim to test the hypothesis that immunity achieved post COVID-19 infection combined with vaccination (hybrid immunity), is more effective against Omicron infection than vaccination alone in a health-care setting. Methods: Data on regular pre-emptive PCR testing from all Health-Care Workers (HCWs) at Laiko University Hospital from 29th December 2020, date on which the national COVID-19 immunization program began in Greece, until 24th May 2022, were retrospectively collected and recorded. The infection rate was calculated after December 21st, 2021, when Omicron was the predominant circulating variant in Greece, as the total number of infections (positive PCR COVID-19 test regardless of symptoms) divided by the total person-months at risk. Results: Of 1, 305 vaccinated HCWs who were included in the analysis [median age of 47 (IQR: 36, 56) years, 66.7 % women], 13 % and 87 % had received 2 or 3 vaccine doses (full and booster vaccination), respectively. A COVID-19 infection had occurred in 135 of 1, 305 of participants prior to Omicron predominance. Of those 135 HCWs with hybrid immunity only 13 (9.6 %) were re-infected. Of the 154 and 1, 016 HCWs with full and booster vaccination-induced immunity, respectively, 71 (46.1 %, infection rate 13.4/100 person-months) and 448 (44.1 %, infection rate 12.2/100 person-months) were infected during the follow up period. No association between gender or age and COVID-19 infection was found and none of the participants had a severe infection or died. Conclusions: Hybrid immunity confers higher protection by almost 5-fold compared to full or booster vaccination for COVID-19 infection with the Omicron variant among HCWs who are at high risk of exposure. This may inform public health policies on how to achieve optimal immunity in terms of the timing and mode of vaccination.