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Frequently Asked Questions on COVID-19 Epidemiology, Prevention, and Clinical Management

Arthur Kim, MD
Sharon R. Lewin, AO, FRACP, PhD, FAHMS
Renslow Sherer, MD
Released: June 1, 2022

The Omicron Era: Questions and Answers

Which monoclonal antibody treatments are effective against the omicron variant and its subvariants?

Short Answer: Sotrovimab maintains activity against omicron BA.1, and bebtelovimab has activity against BA.2.

Arthur Kim, MD (April 22, 2022):
Sotrovimab, which works by targeting nonreceptor-binding domain epitopes, was initially the only monoclonal antibody indicated for treatment of COVID-19 that maintained its activity against the original omicron variant.[Aggarwal 2021] Its potency against omicron is reduced 3-fold compared with its potency against the ancestral virus; it has no activity against the omicron BA.2 subvariant, and its use is currently not advised given the large amount of circulating BA.2.[Cameroni 2021; FDA Sotrovimab]

Tixagevimab plus cilgavimab has substantially reduced activity against the omicron variant but has a 50% inhibitory concentration within the range of possible activity.[Planas 2022] It has retained its activity against the BA.2 subvariant[Takashita 2022] but is now recommended at double the dose from when it was originally authorized to overcome barriers to omicron neutralization.[FDA Tixagevimab] Tixagevimab plus cilgavimab is authorized for pre-exposure prophylaxis—not treatment—for COVID-19.[FDA Tixagevimab]

Bebtelovimab is a newer monoclonal antibody for the treatment of COVID-19 that has demonstrated neutralizing activity against omicron, including the BA.2 subvariant. The FDA issued an EUA for bebtelovimab in February 2022 based on phase II clinical trial data from the BLAZE-4 study.[FDA Bebtelovimab; Dougan 2022]

Have breakthrough COVID-19 infections occurred in patients receiving pre-exposure prophylaxis with tixagevimab plus cilgavimab?

Short Answer: Because of reduced potency against omicron, it’s possible.

Arthur Kim, MD (April 22, 2022):
The FDA has issued an EUA for tixagevimab plus cilgavimab for pre-exposure prophylaxis in patients aged 12 years or older who weigh ≥40 kg who have a contraindication COVID-19 vaccination or who have severe immunocompromise.[FDA Tixagevimab] Its use is intended to prevent COVID-19 infection in those who cannot be vaccinated due to severe allergic reaction and to prevent breakthrough infections in those who are vaccinated but immunocompromised. Tixagevimab plus cilgavimab has 12- to 30-fold reduced potency against the omicron variant compared with the ancestral virus and the clinical significance of this reduced potency is not yet fully understood. However, based on this information it is possible for COVID-19 breakthrough infections to occur in those who receive tixagevimab plus cilgavimab for pre-exposure prophylaxis.[JAMA 2022]

Because of decreased neutralization activity against omicron subvariants BA.1 and BA.1.1, the initial dose of tixagevimab plus cilgavimab is now 300 mg of each agent administered as 2 separate, consecutive IM injections.[FDA Tixagevimab]

What is the frequency of repeat infections with the omicron variant?

Short answer: Repeat infections with SARS-CoV-2 variants, including omicron, are possible. Prior infection and vaccination are protective against reinfections.

Sharon R. Lewin, AO, FRACP, PhD, FAHMS (February 3, 2022):
Reinfections with SARS-CoV-2 are possible. After recovering from a COVID-19 infection, most patients will have some protection against repeat infections; vaccination strengthens that protection.[CDC Reinfection] Reinfection data are still being collected during the omicron phase. Self-reported data from the United Kingdom demonstrated that nearly two thirds of patients infected with the omicron variant during January 2022 had a documented prior SARS-CoV-2 infection.[Elliott 2022]

Is there value in receiving an omicron-specific vaccination after receiving a full vaccine series with one of the currently authorized COVID-19 vaccines?

Short answer: Studies are underway.

Sharon R. Lewin, AO, FRACP, PhD, FAHMS (February 3, 2022):
Pfizer and BioNTech, in partnership, recently began clinical trials investigating the safety and efficacy of an omicron-based vaccine.[Pfizer] The vaccine is being studied in adults aged 18-55 years in 1 of 3 cohorts:

  1. Those who received 2 doses of the current BNT162b2 vaccine 90-180 days prior to enrollment
  2. Those who received 3 doses of the current BNT162b2 vaccine 90-180 days prior to enrollment
  3. Vaccine-naive participants

It will be important to review the results of this study prior to making any recommendations regarding the place in therapy of an omicron-specific vaccine.

Moderna also is developing a redesigned bivalent COVID-19 vaccine that has produced stronger immunity against omicron than previous vaccines.[Moderna Announces] 

How effective are currently available COVID-19 vaccines against the omicron variant?

Short answer: Three, or, if indicated, 4 doses of COVID-19 vaccine are more effective than two against symptomatic disease, hospitalization, and death from the omicron variant.

Sharon R. Lewin, AO, FRACP, PhD, FAHMS (February 3, 2022):
Currently available vaccines are most effective against symptomatic disease, hospitalization, and death when 3 doses have been administered.[UK Health Security Agency] There is variability in effectiveness after 2 doses and that effectiveness wanes over time. For example, a 2-dose series is 25% to 70% effective against symptomatic disease with COVID-19 infection, but that effectiveness decreases to nearly zero 20-25 weeks after the second dose was administered.[UK Health Security Agency] Effectiveness is recovered with a booster dose; after a booster, the effectiveness against symptomatic disease increases to 60% to 75%, and effectiveness against hospitalization and death increases as high as 95%.[UK Health Security Agency]

What is the risk of COVID-19 infection during the omicron era in the pediatric population?

Short answer: Higher than with earlier variants.

Sharon R. Lewin, AO, FRACP, PhD, FAHMS (February 3, 2022):
Omicron infections have been prevalent in the pediatric population but have been associated with less severe infection. Like the adult population, numerically more pediatric patients have been infected with the omicron variant, and subsequently, pediatric hospitalization rates increased during the omicron era. However, compared with the delta variant period, risk for emergency department visits and hospitalizations in pediatric patients has been significantly less in the omicron period. This suggests that the clinical outcomes have been milder compared with the preceding delta variant period.[Wang 2022]

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