The rapid spread of the SARS-CoV-2 Omicron variant suggests that the virus might become globally dominant. Further, the high number of mutations in the viral spike-protein raised concerns that the virus might evade antibodies induced by infection or vaccination. Here, we report that the Omicron spike was resistant against most therapeutic antibodies but remained susceptible to inhibition by Sotrovimab. Similarly, the Omicron spike evaded neutralization by antibodies from convalescent or BNT162b2-vaccinated individuals with 10- to 44-fold higher efficiency than the spike of the Delta variant. Neutralization of the Omicron spike by antibodies induced upon heterologous ChAdOx1/BNT162b2-vaccination or vaccination with three doses of BNT162b2 was more efficient, but the Omicron spike still evaded neutralization more efficiently than the Delta spike. These findings indicate that most therapeutic antibodies will be ineffective against the Omicron variant and that double immunization with BNT162b2 might not adequately protect against severe disease induced by this variant.

SUMMARYThe rapid spread of the SARS-CoV-2 Omicron variant suggests that the virus might become globally dominant. Further, the high number of mutations in the viral spike-protein raised concerns that the virus might evade antibodies induced by infection or vaccination. Here, we report that the Omicron spike was resistant against most therapeutic antibodies but remained susceptible to inhibition by Sotrovimab. Similarly, the Omicron spike evaded neutralization by antibodies from convalescent or BNT162b2-vaccinated individuals with 10- to 44-fold higher efficiency than the spike of the Delta variant. Neutralization of the Omicron spike by antibodies induced upon heterologous ChAdOx1/BNT162b2-vaccination or vaccination with three doses of BNT162b2 was more efficient, but the Omicron spike still evaded neutralization more efficiently than the Delta spike. These findings indicate that most therapeutic antibodies will be ineffective against the Omicron variant and that double immunization with BNT162b2 might not adequately protect against severe disease induced by this variant.

Currently approved viral vector-based and mRNA-based vaccine approaches against coronavirus disease 2019 (COVID-19) consider only homologous prime-boost vaccination. After reports of thromboembolic events, several European governments recommended using AstraZeneca’s ChAdOx1-nCov-19 (ChAd) only in individuals older than 60 years, leaving millions of already ChAd-primed individuals with the decision to receive either a second shot of ChAd or a heterologous boost with mRNA-based vaccines. However, such combinations have not been tested so far. We used Hannover Medical School’s COVID-19 Contact Study cohort of healthcare professionals to monitor ChAd-primed immune responses before and 3 weeks after booster with ChAd (n = 32) or BioNTech/Pfizer’s BNT162b2 (n = 55). Although both vaccines boosted prime-induced immunity, BNT162b2 induced significantly higher frequencies of spike-specific CD4+ and CD8+ T cells and, in particular, high titers of neutralizing antibodies against the B.1.1.7, B.1.351 and P.1 variants of concern of severe acute respiratory syndrome coronavirus 2.

Neutralizing antibodies targeting the receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) block severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry into cells via surface-expressed angiotensin-converting enzyme 2 (ACE2). We used a surrogate virus neutralization test (sVNT) and SARS-CoV-2 S protein-pseudotyped vesicular stomatitis virus (VSV) vector-based neutralization assay (pVNT) to assess the degree to which serum antibodies from coronavirus disease 2019 (COVID-19) convalescent patients interfere with the binding of SARS-CoV-2 S to ACE2. Both tests revealed neutralizing anti-SARS-CoV-2 S antibodies in the sera of ~90% of mildly and 100% of severely affected COVID-19 convalescent patients. Importantly, sVNT and pVNT results correlated strongly with each other and to the levels of anti-SARS-CoV-2 S1 IgG and IgA antibodies. Moreover, levels of neutralizing antibodies correlated with the duration and severity of clinical symptoms but not with patient age. Compared to pVNT, sVNT is less sophisticated and does not require any biosafety labs. Since this assay is also much faster and cheaper, sVNT will not only be important for evaluating the prevalence of neutralizing antibodies in a population but also for identifying promising plasma donors for successful passive antibody therapy.

There have been concerns about high rates of thus far undiagnosed SARS-CoV-2 infections in the health-care system. The COVID-19 Contact (CoCo) Study follows 217 frontline health-care professionals at a university hospital with weekly SARS-CoV-2-specific serology (IgA/IgG). Study participants estimated their personal likelihood of having had a SARS-CoV-2 infection with a mean of 21% [median 15%, interquartile range (IQR) 5-30%]. In contrast, anti-SARS-CoV-2 IgG prevalence was about 1-2% at baseline. Regular anti-SARS-CoV-2 IgG testing of health-care professionals may aid in directing resources for protective measures and care of COVID-19 patients in the long run. Keywords COVID-19 • SARS-CoV-2 • Immunoglobulin • IgG • IgA • Health-care worker • ELISA • Seroprevalence • Diagnostics • Health-care professionals Abbreviations COVID-19 Coronavirus disease 19 ELISA Enzyme-linked immunosorbent assay IgG Immunoglobulin G PCR Real-time polymerase chain reaction SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 Despite growing access of broadly available testing systems, uncertain rates of asymptomatic infections have raised concerns about a potentially high rate of thus far undiagnosed SARS-CoV-2 infections, particularly in frontline medical staff [1]. To prevent the breakdown of health-care systems during the current pandemic, the protection of medical personnel and patients from contracting a SARS-CoV-2 infection is central [2]. Consent finding for case definition, COVID-19 diagnosis in suspected cases, and scaling up of suitable diagnostic systems have been challenging since the start of the pandemic. Real-time polymerase chain reaction (PCR)-based nasopharyngeal (or throat) swab testing was rapidly developed and has helped in ascertainment and tracking of the SARS-CoV-2 outbreak [2]. However, the sensitivity of PCR-based testing, which is thus far only applied routinely for symptomatic patients, crucially depends on the timing and type of respiratory sampling and led to false negative rates of up to 70% during the early phase of the pandemic [3, 4]. Serological testing for SARS-CoV-2-specific immunoglobulins (Ig) is relatively easy, inexpensive, and critical for epidemiological studies. SARS-CoV-2-specific B cell responses appear to correlate to disease severity with rising antibody titers typically between 5 to 10 days and fully positive rates at about 18 days after symptom onset [5]. As such, serological testing can be helpful in suspected cases with negative PCR results and in identification of asymptomatic infections [6]. We initiated the COVID-19 Contact (CoCo) study to weekly monitor SARS-CoV-2-specific serology (IgA/IgG) Christine Happle and Alexandra Jablonka contributed equally to this work.