The Vaccine Efficacy Against the SARS-CoV-2 Omicron: A Systemic Review and Meta-Analysis

Abstract

BackgroundCOVID-19 is a respiratory illness caused by SARS-CoV-2. The most recent variant is Omicron (line B.1.1.529), which was first identified in South Africa in November 2021. The concern with this variant is the ineffectiveness of vaccines currently available. We aim to systematically evaluate the effectiveness of the currently available COVID-19 vaccines and boosters for the Omicron variant.MethodsWe searched the PubMed, Embase, the Cochrane Library and Web of Science databases from inception to June 5th, 2022. Studies that examined the effectiveness of SARS-CoV-2 vaccines against the Omicron variant infection were included. Random-effects model was used to estimate the pooled vaccine effectiveness against the Omicron variant.ResultsA total of 13 studies were included to evaluate the effectiveness of the vaccine against the Omicron variant, and 11 studies were included to compare the effectiveness between the two-dose and three-dose (booster) vaccinations. Full vaccination (two-dose with or without booster) showed a protective effect against the Omicron variant compared to no vaccination (OR = 0.62, 95% CI: 0.56–0.69), while the effectiveness decreased significantly over 6 months after the last dose. The two-dose vaccination plus booster provided better protection against the Omicron variant compared to the two-dose vaccination without booster (OR = 0.60, 95% CI: 0.52–0.68). Additional analysis was performed for the most commonly used vaccines in the United Staes: BNT162b2(Pfizer) (OR = 0.65, 95% CI: 0.52–0.82) and mRNA-1273(Moderna) (OR = 0.67, 95% CI: 0.58–0.88) vaccines in the US, which showed similar effectiveness compared to no vaccination.ConclusionsThe full dose of SARS-CoV-2 vaccination effectively reduces infection from the SARS-CoV-2 Omicron variant; however, the effectiveness wanes over time. The booster vaccine provides additional protection against the Omicron variant.

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“…Studies showed that vaccine effectiveness after receipt of both 2 and 3 doses was lower during the Omicron-predominant period than during the Delta-predominant period, and that the effectiveness of the booster dose is decreasing over time [20] , [21] . In accordance with this, our study did not find a significant difference between having a booster dose or not in the rate of SARS-CoV-2 infection.…”

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“…The study period coincided with the third pandemic wave in Croatia and the rise of the SARS-CoV-2 B.1.1.7 (Alpha) variant for which attenuated vaccine efficacy was observed, a continuing trend for variants of concern that followed [ 43 , 44 , 45 ]. Compared to healthy controls, hematologic patients showed an even faster decline in neutralizing antibody titers for B.1.351 (Beta) and B.167.2 (Delta) variants [ 46 ].…”

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“…The functional humoral response after vaccination was lower against variants of concern (VOC) (i.e., Alpha, Beta, and Delta) vs wildtype [ 8 ]. More recently, the VOC Omicron has also raised concerns [ 9 ]. Even after booster dose administration, vaccination neutralization against the Omicron variant was lower than against other VOC [ 9 , 10 , 11 , 12 ].…”

“…More recently, the VOC Omicron has also raised concerns [ 9 ]. Even after booster dose administration, vaccination neutralization against the Omicron variant was lower than against other VOC [ 9 , 10 , 11 , 12 ]. In addition, numerous factors influence vaccine effectiveness.…”