Increased household transmission and immune escape of the SARS-CoV-2 Omicron variant compared to the Delta variant: evidence from Norwegian contact tracing and vaccination data

Abstract

We compared the secondary attack rate (SAR) of the SARS-CoV-2 Omicron and Delta variants in households using contact tracing data. Omicron SAR was higher (41%) than Delta (35%), likely due to immune evasion. Booster dose reduces risk of infection but has limited effect on preventing Omicron transmission.

Breakthrough infections after COVID-19 vaccination: Insights, perspectives and challenges

“…It is worth investigating if a fourth dose of vaccination is qualitatively different from the third or whether the protection levels will return to the pre-boost level afterwards [ 76 ]. A practical issue that needs to be addressed is whether a longer interval in booster doses may effectively increase immunogenicity and protection from symptomatic breakthrough infections.…”

“…Also, there is an increasing need to monitor duration of protection and vaccine effectiveness against different variants [ [73] , [74] , [75] , [76] , [77] , [78] , [79] , [80] , [81] , [82] , [83] , [84] , [85] , [86] , [87] , [88] ]. Such a system will be efficient in promptly adapting vaccine antigens and dosing intervals, as required.…”

A Recombinant VSV-Based Bivalent Vaccine Effectively Protects against Both SARS-CoV-2 and Influenza A Virus Infection

“…Notably, the continuing emergence of COVID-19 VOC has decreased the licensed vaccine’s effectiveness in terms of preventing infection ( 45 – 47 ). Particularly, the newly emerged Omicron possesses an extensive number of mutations compared with other variants ( 8 ) and the rapid spread of this VOC was facilitated by its high transmissibility and immune evasion ability ( 9 , 48 ). Therefore, it is necessary to assess whether EM2e/SPΔC1 vaccine could induce broad NAbs against different SARS-CoV-2 variants.…”

The effect of vaccination on transmission of SARS-CoV-2 (COVID-19): a rapid review

“…In this update, there were 6 observational studies that directly assessed the effectiveness of vaccines in reducing the risk of transmission of SARS-CoV-2 from people who had COVID-19 (index cases) to household members or close contacts (secondary cases). Four of the studies were pre-prints: Allen et al (2022a), Jalali et al (2022), Lyngse et al (2022a), Sriraman et al (2022). The six studies were appraised using the Quality Criteria Checklist (QCC) tool.…”

“…The six studies were appraised using the Quality Criteria Checklist (QCC) tool. Two studies were assessed as high quality (Andrejko et al 2021, Lyngse et al 2022a, three were of medium quality (Allen et al 2022a, Jalali et al 2022, Sriraman et al 2022) and one study was of low quality (Brandal et al 2021). Five were cohort studies (Allen et al 2022a, Brandal et al 2021, Jalali et al 2022, Lyngse et al 2022a, Sriraman et al 2022 and one was a case-control study (Andrejko et al 2021) One study provided data from the UK (Allen et al 2022a), three from Europe (Brandal et al 2021, Jalali et al 2022, Lyngse et al 2022a, one from Asia (Sriraman et al 2022) and one from USA (Andrejko et al 2021).…”