Scientists discover diminished vaccine efficacy in opposition to Omicron in South Africa and 50 different nations

In a latest research posted to the medRxiv* pre-print server, a staff of researchers evaluated the influence of extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant on the prevalence of SARS-CoV-2 infections amongst unvaccinated and vaccinated populations of South Africa and 50 different nations.

Study: Using Survey Data to Estimate the Impact of the Omicron Variant on Vaccine Efficacy against COVID-19 Infection. Image Credit: G.Tbov/ShutterstockResearch: Utilizing Survey Knowledge to Estimate the Influence of the Omicron Variant on Vaccine Efficacy in opposition to COVID-19 An infection. Picture Credit score: G.Tbov/Shutterstock

The College of Maryland World COVID-19 Developments and Influence Surveys (UMD World CTIS) had collected greater than 100,000 responses from the world over, associated to coronavirus illness 2019 (COVID-19) signs, habits, testing, and vaccination standing. 

Concerning the research

For the current research, the researchers accessed the UMD World CTIS information and information of SARS-CoV-2 genome sequencing from the worldwide initiative on sharing all influenza information (GISAID).

They eliminated irregular responses of the members who declared to have all of the COVID-19 signs or reported uncommon values (larger than 100) within the quantitative questions of the survey.

To carefully monitor the evolution of energetic COVID-19 instances, they derived a proxy for energetic COVID-19 instances utilizing a Random Forest classifier. The corresponding outcomes or proxy estimates had been labeled Random Forest, UMD COVID-like sickness (CLI), Stringent CLI, Basic CLI, and Broad CLI. They in contrast every proxy estimate with the estimate of energetic COVID-19 instances, as described by Alvarez et al., the place every new case was assumed to stay energetic for 10 days. These final estimates had been referred to as Confirmed, and each Confirmed and the estimates utilizing the assorted proxies led to time sequence with one estimated worth of vaccine efficacy (VE) per day.

Random Forest classifier was versatile and adaptive, therefore researchers had been in a position to create a number of fashions per nation with this mannequin, permitting capturing and adapting to facets that diversified over time, like the extent of vaccination and the surge of recent SARS-CoV-2 variants.

To acquire the official take a look at positivity charges (TPR) utilizing our world in information (OWID TPR) dataset from June 18, 2021, to December 31, 2021, the researchers chosen 20 nations that had the most important variety of accessible responses within the UMD World CTIS dataset together with South Africa.

In South Africa, the lower in VE was evaluated from mid-June 2021 till the top of 2021, extra particularly, in three time durations of 1 month every i) June 18 to July 18, 2021; ii) August 9 to September 6, 2021; and December 1 to 31, 2021 (dominated by Omicron). The researchers studied the Gauteng province in South Africa individually, because it was among the many most severely affected by Omicron. 

In all, the researchers studied 50 nations for which the UMD World CTIS had the most important quantity of knowledge and computed the VE for 2 months – October and December 2021. Throughout this time, the VE estimates had been in contrast utilizing the Random Forest identifier amongst all three vaccination teams utilizing correlation evaluation.

Solely non-negative VE values in a pattern dimension of a minimal of 1000 samples, which confirmed prevalences PV and PU of a minimum of 0.01, had been thought of.


The outcomes confirmed the presence of a measurable drop in vaccine efficacy from 0.62 within the Delta interval to 0.24 within the Omicron interval in South Africa. As well as, these outcomes confirmed that having two vaccine doses conferred higher safety than one dose, throughout each durations, dominated by Delta (0.81 versus 0.51) and Omicron (0.30 versus 0.09). Nevertheless, the outcomes didn’t point out the standing of respondents in relation to a booster dose.

By January 7, 2022, a restricted variety of nations exhibited a excessive Omicron prevalence with a excessive degree of sequencing information supporting it. Nonetheless, upon extending the research evaluation to different nations the place Omicron was detected, evaluating the scenario in October (earlier than Omicron’s emergence) with that of December 2021 confirmed a mean drop in vaccine efficacy from 0.53 to 0.45 amongst these vaccinated with two doses. As well as, a big unfavourable (Pearson) correlation ~0.6 between the measured prevalence of Omicron and the VE was noticed.

Of all of the 5 proxies, the Random Forest proxy was essentially the most promising, because it exhibited the best correlation values for many nations. Of the 21 nations for which TPR values had been estimated, 17 nations exhibited low TPR values of ≤ 0.1 in both official or survey-based TPR, and 11 exhibited low values for each, with 7 having values below 0.053. These findings instructed that these nations saved COVID-19 case counts comparatively below management and reported information accurately.


To summarize, the current research remarkably tracked the prevalence of COVID-19 infections utilizing each day participatory symptom surveillance information, significantly these with stronger surveillance techniques and constant TPRs.

The authors cautioned that the noticed discount of VE within the Omicron interval is in the direction of COVID-19 an infection and impacts Omicron transmission however doesn’t suggest a VE discount in relation to COVID-19 severity, hospitalization, and dying. Additional research ought to verify these outcomes as soon as Omicron turns into dominant in different nations.

*Vital discover

medRxiv publishes preliminary scientific studies that aren’t peer-reviewed and, due to this fact, shouldn’t be thought to be conclusive, information scientific follow/health-related conduct, or handled as established data.

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