Evidence on COVID-19 vaccine effectiveness and period of safety towards Omicron
  • Reading time:5 min(s) read

In a latest research posted to the medRxiv* preprint server, researchers reported the vaccine effectiveness (VE) and period of immunity towards extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron.

Study: Facing the Omicron variant – How nicely do vaccines shield towards delicate and extreme COVID-19? Third interim evaluation of a residing systematic assessment. Image Credit: Dkoi/Shutterstock

Since its emergence in late November 2021, the Omicron variant has quickly unfold worldwide, changing beforehand dominant variants. Elevated charges of symptomatic or asymptomatic an infection in totally vaccinated people and convalescents increase considerations in regards to the effectiveness of present vaccines towards SARS-CoV-2 Omicron.

About the research

In the current research, researchers reported outcomes from an interim evaluation of a residing systematic assessment (LSR) summarizing proof on VE and period of safety towards SARS-CoV-2 Omicron. For the LSR, the researchers included research investigating VE towards SARS-CoV-2 an infection amongst folks aged 12 years or older for European Medicine Agency (EMA) permitted vaccines.

For the present evaluation, solely the research which investigated the talked about outcomes resulting from SARS-CoV-2 Omicron or throughout the Omicron interval have been thought of. The coronavirus illness 2019 (COVID-19) literature database created by the Robert Koch Institute (RKI) library was looked for research revealed from October 23, 2021, to January 14, 2022, no matter publication standing or language.

Additional research have been recognized by hand-search or meta-search of internet sites until February 11, 2022. Studies with potential relevance have been screened on the title or summary and full-text stage. The VE knowledge throughout the next three comparisons have been thought of – 1) major sequence vs. no vaccination, 2) major vs. booster vaccination, and three) booster vs. no vaccination.

The major outcomes have been analyzing VE towards SARS-CoV-2 an infection confirmed by polymerase chain response (PCR) or antigen checks, symptomatic or extreme COVID-19. VE knowledge have been stratified based mostly on the time since vaccination: 14 days, 14 days to a few months, three to 6 months, and greater than six months. The researchers assessed the % distinction of VE over time for research reporting estimates for no less than two-time factors.


The staff recognized greater than 8,400 entries from the database and 38 by hand-search or meta-search of internet sites. After screening, 26 research have been chosen for knowledge extraction. Most (21) have been non-peer-reviewed; 5 investigated VE towards an infection and related outcomes with the Omicron variant alone. The remaining research included VE estimates towards an infection with SARS-CoV-2 Delta for comparability.

The variant related to an infection was recognized by S-gene goal failure (SGTF) in PCR checks, whole-genome sequencing (WGS), or from recognized time factors of the predominant circulation of SARS-CoV-2 Omicron. Twenty-two research reported VE estimates for major vaccination, whereas 23 reported VE for booster dose. One research in contrast VE after the second booster dose (fourth dose) to after the third dose.

Most research assessed the VE of messenger ribonucleic acid (mRNA) vaccines (13 Pfizer’s BNT162b2, and 9 investigated Moderna’s mRNA-1273). Twelve research examined VE towards any SARS-CoV-2 an infection, i.e., with out differentiating between symptomatic or asymptomatic circumstances. Across all research, VE after 14 days of major vaccination ranged from 0% to 62%.

The research reporting knowledge for no less than two-time factors revealed a decline in VE by 16% to 34% as much as six months with mRNA vaccination. After booster administration, VE throughout all research was 34% to 76% relative to non-vaccinated topics and 14% to 53% relative to these after major vaccination. Twelve or extra days after the fourth dose (second booster), VE towards Omicron an infection was 47%.

Seven research estimated VE towards symptomatic Omicron an infection. VE at 14 days ranged from 6% to 76% throughout these research. For research with estimates on no less than two-time factors, VE dropped by 45% – 63% for mRNA vaccines and 50% for vector-based vaccines as much as six months post-vaccination. VE at 14 days after booster dose was 19% to 73.9% relative to non-vaccinated topics and 50% to 68% in contrast with major vaccination.

Seventeen research estimated VE towards extreme COVID-19. VE at 14 days was 3% to 84% in comparison with non-vaccinated people that dropped to 40% and 15% – 67% by six months put up mRNA and vector-based vaccination, respectively. VE ranged from 12% to 100% at 14 days after booster vaccination and 78% to 93.7% as much as three months put up increase. After the fourth dose (second booster), VE was 75% towards extreme illness assessed at 12 days or later.

From the research that included comparability teams, the chance ratios indicated the next threat for any or symptomatic Omicron an infection than Delta an infection. Nevertheless, the chance of extreme COVID-19 was decrease post-Omicron an infection than Delta an infection in vaccinated folks.


In abstract, these observations revealed that VE after major vaccination was low for COVID-19 vaccines permitted within the European Union however improved post-boost in stopping Omicron infections. Moreover, VE was excessive towards extreme illness, significantly after administering a booster. Vaccine-induced immunity waned quickly after major vaccination however was much less pronounced for extreme COVID-19.

*Important discover

medRxiv publishes preliminary scientific stories that aren’t peer-reviewed and, subsequently, shouldn’t be thought to be conclusive, information scientific apply/health-related habits, or handled as established data.

Journal reference:

  • Külper-Schiek, W. et al. (2022) “Facing the Omicron variant – How well do vaccines protect against mild and severe COVID-19? Third interim analysis of a living systematic review”. medRxiv. doi: 10.1101/2022.05.25.22275516. https://www.medrxiv.org/content material/10.1101/2022.05.25.22275516v1

If you are interested in working in a distraction free environment, visit our site Blissful Noises where we provide various sounds and features to help you focus or relax.