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. 2023 Dec 10;11(12):1836.
doi: 10.3390/vaccines11121836.

Effectiveness of Adapted COVID-19 Vaccines and Ability to Establish Herd Immunity against Omicron BA.1 and BA4-5 Variants of SARS-CoV-2

Pedro Plans-Rubió  1   2
Affiliations

Effectiveness of Adapted COVID-19 Vaccines and Ability to Establish Herd Immunity against Omicron BA.1 and BA4-5 Variants of SARS-CoV-2

Pedro Plans-Rubió. Vaccines (Basel). .

Abstract

The emergence of novel SARS-CoV-2 variants has raised concerns about the ability of COVID-19 vaccination programs to establish adequate herd immunity levels in the population. This study assessed the effectiveness of adapted vaccines in preventing SARS-CoV-2 infection and the ability of the adapted vaccines to establish herd immunity against emerging Omicron variants. A systematic literature review was conducted to estimate the absolute vaccine effectiveness (aVE) in preventing SARS-CoV-2 infection using adapted vaccines targeting Omicron variants. The ability of the adapted vaccines to establish herd immunity was assessed by taking into account the following factors: aVE, Ro values of SARS-CoV-2 and the use of non-pharmacological interventions (NPIs). This study found meta-analysis-based aVEs in preventing severe disease and SARS-CoV-2 infection of 56-60% and 36-39%, respectively. Adapted vaccines could not establish herd immunity against the Omicron BA.1 and BA.4-5 variants without using non-pharmacological interventions (NPIs). The adapted vaccines could establish herd immunity only by achieving >80% vaccination coverage, using NPIs with greater effectiveness and when 20-30% of individuals were already protected against SARS-CoV-2 in the population. New adapted COVID-19 vaccines with greater effectiveness in preventing SARS-CoV-2 infection must be developed to increase herd immunity levels against emerging SARS-CoV-2 variants in the population.

Keywords: COVID-19 vaccination; Omicron BA.1; Omicron BA.4; Omicron BA.5; SARS-CoV-2; adapted COVID-19 vaccines; effectiveness of COVID-19 vaccines; herd immunity against SARS-CoV-2.

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Conflict of interest statement

The author declares no conflict of interest.

Figures

Figure 1
Figure 1
Vaccination coverage (%) required to establish herd immunity against SARS-CoV-2 with reproductive numbers (Ro) from 6 to 12 by effectiveness (%) of adapted SARS-CoV-2 vaccines. Objectives of vaccination coverage of 70%, 80% and 90% indicated with dashed red, blue and green lines, respectively.
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