Triple-vaccinated are 4.5 times more likely to test positive for Omicron infection than the unvaccinated


According to a new study by the ONS (Office for National Statistics) in the UK, triple-vaccinated individuals are 4.5 more likely to test positive for Omicron than unvaccinated individuals. The analysis used data from 1,816 individuals between the dates of November 29th, 2021-December 12th, 2021.

The study PDF can be viewed or downloaded here.

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Screening Characteristic Category Chance of pos. Omicron test
Vaccination status Not vaccinated 1
Vaccination status 1 dose 1.57
Vaccination status 2 doses, more than 14 days ago 2.26
Vaccination status 3 doses, more than 14 days ago 4.45
Previous COVID-19 infection No (Reference) 1
Previous COVID-19 infection Yes 3.22
Work Status Employed, working (Reference) 1
Work Status Employed, not working 0.67
Work Status Not working 0.70
Work Status Retired 0.94
Work Status Child/student 1.62
Travel abroad status (In the last 28 days) No (Reference) 1
Travel abroad status (In the last 28 days) Yes 4.60

Here is the information, as provided by ONS release:

Coronavirus (COVID-19) Infection Survey, UK: Characteristics related to having an Omicron compatible result in those who test positive for COVID-19

Today we have published some early results from the Coronavirus (COVID-19) Infection Survey showing the characteristics of people more likely to be infected with the Omicron variant compared with the Delta variant. These early results are based only on the first fortnight’s data that have sufficient cases for analysis on the Omicron variant, so caution is advised. Fuller analysis based on more data from our survey will be published when available.

Cases compatible with the Omicron variant are characterised by the absence of the ‘S’ gene on a positive test, one of three genes that a PCR test detects, the others being OR and N, and a high viral load. Cases with a high viral load and an absent ‘S’ gene are characterised in this analysis as a potential Omicron case. All other cases are likely to be cases of the Delta variant or its genetic descendants. 

This analysis evaluates, for those who tested as a strong positive (cycle Threshold (Ct) value <30) between 29 November 2021 and 12 December 2021, the characteristics which were associated with individuals who had results compatible with the Omicron variant. Results not compatible with Omicron are suspected Delta cases. These effects show the relative likelihood of having a result compatible with Omicron compared to the reference group for each characteristic studied. 

There are 1,816 positive individuals included in the analysis, of which 115 tested positive compatible with Omicron. See note at end of document for the definition of ‘compatible with Omicron’ and ‘compatible with Delta’.

The model uses a similar process to our usual predictors of positivity analysis, published regularly in our Characteristics of people testing positive release. However, only individuals who test as a strong positive (Ct<30) are included, since weaker positive results of the Delta variant could be identified as compatible with Omicron. The model identifies the probability of these individuals having positive results compatible with Omicron. 

Main Points

Age: Compared to other ages, young children testing positive for COVID-19 are less likely to have infections compatible with the Omicron variant. Those in their 20s and 30s with COVID-19, however, are more likely to have infections compatible with the Omicron variant.

Deprivation: Those infected with COVID-19 who live in more deprived areas are more likely to test positive with infections compatible with the Omicron variant.

Urban: Those infected with COVID-19 and living in major urban areas and urban cities/towns are more like to test positive with infections compatible with the Omicron variant compared to those living in rural areas.

Ethnicity: There is some evidence to suggest that people who test positive, for COVID-19 who report being from ethnic minorities are more likely to test positive with infections compatible with the Omicron variant compared to those who identify themselves as White.

Traveling abroad: Those who travelled abroad in the last 28 days and test positive for COVID-19 are more likely to test positive for infections compatible with the Omicron variant compared to those who did not travel.

Reinfection: Those who have previously been infected with COVID-19 and become reinfected are more likely to test positive for an infection compatible with the Omicron variant, compared with those who test positive with their first infections. 

Vaccination status: Those who have received three doses of a vaccine and test positive for COVID-19 are more likely to be infected with infections compatible with the Omicron variant compared with those who are unvaccinated, though individuals who had received at least one dose of a COVID-19 vaccine continued to be less likely to test positive for COVID-19, regardless of variant. It is too early to draw conclusions from our data on the effectiveness of vaccines against the Omicron variant.



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