Effectiveness of COVID-19 vaccines against the Omicron (B.1.1.529) variant of concern

Abstract

Background A rapid increase in cases due to the SARS-CoV-2 Omicron (B.1.1.529) variant in highly vaccinated populations has raised concerns about the effectiveness of current vaccines. Methods We used a test-negative case-control design to estimate vaccine effectiveness (VE) against symptomatic disease caused by the Omicron and Delta variants in England. VE was calculated after primary immunisation with two BNT162b2 or ChAdOx1 doses, and at 2+ weeks following a BNT162b2 booster. Results Between 27 November and 06 December 2021, 581 and 56,439 eligible Omicron and Delta cases respectively were identified. There were 130,867 eligible test-negative controls. There was no effect against Omicron from 15 weeks after two ChAdOx1 doses, while VE after two BNT162b2 doses was 88.0% (95%CI: 65.9 to 95.8%) 2-9 weeks after dose 2, dropping to between 34 and 37% from 15 weeks post dose 2.From two weeks after a BNT162b2 booster, VE increased to 71.4% (95%CI: 41.8 to 86.0%) for ChAdOx1 primary course recipients and 75.5% (95%CI: 56.1 to 86.3%) for BNT162b2 primary course recipients. For cases with Delta, VE was 41.8% (95%CI: 39.4-44.1%) at 25+ weeks after two ChAdOx1 doses, increasing to 93.8% (95%CI: 93.2-94.3%) after a BNT162b2 booster. With a BNT162b2 primary course, VE was 63.5% (95%CI: 61.4 to 65.5%) 25+ weeks after dose 2, increasing to 92.6% (95%CI: 92.0-93.1%) two weeks after the booster. Conclusions Primary immunisation with two BNT162b2 or ChAdOx1 doses provided no or limited protection against symptomatic disease with the Omicron variant. Boosting with BNT162b2 following either primary course significantly increased protection.

Homologous or Heterologous Booster of Inactivated Vaccine Reduces SARS-CoV-2 Omicron Variant Escape from Neutralizing Antibodies

“…However, the good news is that after two doses of inactivated vaccines as the “priming” shot, a third homologous inactivated vaccine booster or a heterologous protein subunit vaccine booster could elevate neutralization titer against Omicron. Our results are quite comparable to studies on the same inactivated vaccine 23 or other vaccines 25 , and again supported by the real-world data showing a third dose booster vaccination provides increased protection against Omicron 26 .…”

Two doses of mRNA vaccine elicit cross-neutralizing memory B-cells against SARS-CoV-2 Omicron variant

“…However, the clinical relevance of such B mem cell reactivity during protective immunity in humans remains unknown. We demonstrated that the majority of human B mem cells elicited by two doses of mRNA vaccine are able to capture SARS-CoV-2 variants, despite the striking resistance of the variants to pre-existing antibodies ( 12–14, 16, 17 ). Moreover, such memory cross-reactivity was linked to the cross-neutralizing activities against the variants including highly mutated Omicron variant.…”

“…In particular, the Omicron variant drastically reduced the neutralizing activity of circulating antibodies in fully vaccinated individuals and many therapeutic monoclonal antibodies in clinical use ( 12–16 ). Epidemiological evidence further suggest a reduction in the vaccine effectiveness against this variant ( 17 ).…”

Striking Antibody Evasion Manifested by the Omicron Variant of SARS-CoV-2

“…These findings are in line with emerging clinical data on the Omicron variant demonstrating higher rates of reinfection 11 and vaccine breakthroughs. In fact, recent reports showed that the efficacy of two doses of BNT162b2 vaccine has dropped from over 90% against the original SARS-CoV-2 strain to approximately 40% and 33% against B.1.1.529 in the United Kingdom 32 and South Africa 33 , respectively. Even a third booster shot may not adequately protect against Omicron infection 32,34 , but of course it is advisable to do so.…”