Prevention of SARS-CoV-2 Infection
Last Updated: September 26, 2022
|Rating of Recommendations: A = Strong; B = Moderate; C = Weak|
Rating of Evidence: I = One or more randomized trials without major limitations; IIa = Other randomized trials or subgroup analyses of randomized trials; IIb = Nonrandomized trials or observational cohort studies; III = Expert opinion
General Prevention Measures
Transmission of SARS-CoV-2 is thought to occur primarily through exposure to respiratory droplets. Exposure can occur when someone inhales droplets or particles that contain the virus (with the greatest risk of transmission occurring within 6 feet of an infectious source) or touches their mucous membranes with hands that have been contaminated with the virus. Exhaled droplets or particles can also deposit the virus onto exposed mucous membranes.1
Less commonly, airborne transmission of small droplets and particles of SARS-CoV-2 to people farther than 6 feet away can occur; in rare cases, people passing through a room that was previously occupied by an infectious person may become infected. SARS-CoV-2 infection via airborne transmission of small particles tends to occur after prolonged exposure (i.e., >15 minutes) to an infectious person who is in an enclosed space with poor ventilation.1
The risk of SARS-CoV-2 transmission can be reduced by covering coughs and sneezes and maintaining a distance of at least 6 feet from others. When consistent distancing is not possible, face coverings may reduce the spread of infectious droplets from individuals with SARS-CoV-2 infection to others. Frequent handwashing also effectively reduces the risk of infection.2 Health care providers should follow the Centers for Disease Control and Prevention (CDC) recommendations for infection control and the appropriate use of personal protective equipment.3
Vaccination is the most effective way to prevent SARS-CoV-2 infection. The COVID-19 Treatment Guidelines Panel (the Panel) recommends COVID-19 vaccination as soon as possible for everyone who is eligible according to the CDC’s Advisory Committee on Immunization Practices (AI). Three vaccines are authorized or approved for use in the United States to prevent COVID-19. For primary and booster vaccinations, the mRNA vaccines (i.e., BNT162b2 [Pfizer-BioNTech] or mRNA-1273 [Moderna]) are preferable to the Ad26.COV2.S (Johnson & Johnson/Janssen) vaccine due to its risk of serious adverse events.4 A primary series of COVID-19 vaccinations is recommended for everyone aged ≥6 months in the United States. Certain groups of people should receive additional doses at specified intervals after the primary series of vaccinations. The type and dose of vaccine and the timing of these additional doses depend on the recipient’s age and underlying medical conditions. The CDC regularly updates the clinical considerations for use of the COVID-19 vaccines that are currently approved by the Food and Drug Administration (FDA) or authorized for use in the United States.5
COVID-19 vaccines are safe and effective. Local and systemic adverse events are relatively common with these vaccines. Most of the adverse events that occurred during vaccine trials were mild or moderate in severity (i.e., they did not prevent vaccinated people from engaging in daily activities) and resolved after 1 or 2 days. There have been a few reports of severe allergic reactions following COVID-19 vaccination, including rare reports of patients who experienced anaphylaxis after receiving an mRNA vaccine.6,7
Reports have suggested that there is an increased risk of thrombosis with thrombocytopenia syndrome (TTS) in adults who have received the Ad26.COV2.S vaccine7 and, rarely, the mRNA-1273 vaccine.8 TTS is a rare but serious condition that causes blood clots in large blood vessels and low platelet levels. Women aged 30 to 49 years should be aware of the increased risk of TTS. The American Society of Hematology and the American Heart Association/American Stroke Association Stroke Council leadership have published considerations that are relevant to the diagnosis and treatment of TTS that occurs in people who receive the Ad26.COV2.S vaccine.9,10 These considerations include information on administering a nonheparin anticoagulant and intravenous immunoglobulin to these patients. Given the rarity of this syndrome and the unique treatment required, consider consulting a hematologist when treating these patients.
Myocarditis and pericarditis after COVID-19 vaccination are rare, and most of the reported cases were very mild and self-limiting.11 These conditions have occurred most often in male adolescents, young adults, and people who have received mRNA vaccines.
Guillain-Barré syndrome (GBS) in people who received the Ad26.COV2.S vaccine is rare.11 GBS is a neurologic disorder that causes muscle weakness and sometimes paralysis. Most people with GBS fully recover, but some have permanent nerve damage. Onset typically occurs about 2 weeks after vaccination. GBS has mostly been reported in men aged ≥50 years.
The CDC provides regular updates on selected adverse events of COVID-19 vaccines on its website.
Vaccination in Pregnant or Lactating People
Pregnant and lactating individuals were not included in the initial COVID-19 vaccine trials. However, the CDC, the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine recommend vaccination for pregnant and lactating people based on the accumulated safety and efficacy data on the use of these vaccines in pregnant people, as well as the increased risk of severe disease in pregnant individuals with COVID-19.12-17 These organizations also recommend vaccination for people who are trying to become pregnant or who may become pregnant in the future. The ACOG publication includes a guide for clinicians on counseling pregnant patients about COVID-19 vaccination.18
Anti-SARS-CoV-2 Monoclonal Antibodies
Vaccination remains the most effective way to prevent SARS-CoV-2 infection and should be considered the first line of prevention. However, some individuals cannot or may not mount an adequate protective response to COVID-19 vaccines. Others may not have been fully vaccinated because they have a history of severe adverse reactions to a COVID-19 vaccine or its components.
On the basis of results from PROVENT, a large randomized controlled trial conducted when the major circulating SARS-CoV-2 variants were Alpha, Beta, Delta, and Epsilon,19 the FDA issued an Emergency Use Authorization (EUA) for the anti-SARS-CoV-2 monoclonal antibodies (mAbs) tixagevimab plus cilgavimab (Evusheld).20 The EUA allows these anti-SARS-CoV-2 mAbs to be used as pre-exposure prophylaxis (PrEP) for certain individuals who are immunocompromised and therefore may have inadequate responses to COVID-19 vaccines or are unable to be fully vaccinated due to a history of severe adverse reactions to a COVID-19 vaccine. A modification in the fragment crystallizable (Fc) region gives these anti-SARS-CoV-2 mAbs prolonged half-lives, resulting in potential protection from SARS-CoV-2 infection for up to 6 months, depending on the variant.
The PROVENT trial used tixagevimab 150 mg plus cilgavimab 150 mg, which was the dose initially authorized by the FDA. However, in vitro data showed that some subvariants of the Omicron variant had decreased susceptibility to tixagevimab plus cilgavimab. Because of these findings, in February 2022, the FDA revised the EUA to authorize the use of an increased dose of tixagevimab 300 mg plus cilgavimab 300 mg.20-23 For patients who previously received a dose of tixagevimab 150 mg plus cilgavimab 150 mg, the FDA EUA suggested administering an second dose; the specific dose depends on the amount of time that has passed since the initial dose (see below). On June 30, 2022, the FDA further revised the EUA to authorize repeated doses of tixagevimab 300 mg plus cilgavimab 300 mg to be administered every 6 months.
When prescribing tixagevimab plus cilgavimab for SARS-CoV-2 PrEP, clinicians should be aware of the following:
- Tixagevimab plus cilgavimab is authorized for use as PrEP in a population that was not well represented in the PROVENT trial (i.e., a very small proportion of the participants were immunocompromised).
- There are no clinical trial efficacy data on the use of tixagevimab 300 mg plus cilgavimab 300 mg for the prevention of symptomatic COVID-19, and there are no data for any repeated dose at any defined interval, including for the authorized schedule of repeat dosing every 6 months proposed in the latest EUA. This dose and the strategy of repeating the dose every 6 months are based on pharmacokinetic/pharmacodynamic (PK/PD) modeling data.24 Substantial uncertainty in the PK/PD model remains.
- The tixagevimab 150 mg plus cilgavimab 150 mg dose initially authorized by the FDA may not be sufficient to prevent cases of COVID-19 caused by the Omicron BA.1 and BA.1.1 subvariants. No clinical data and only limited PK/PD data guide the administration of repeat doses of tixagevimab plus cilgavimab in those who were previously treated with tixagevimab 150 mg plus cilgavimab 150 mg. Simulations based on population PK models suggest that administering an additional dose of tixagevimab 150 mg plus cilgavimab 150 mg ≤3 months after the initial dose will allow a patient to achieve drug concentrations approximating those observed in people who received tixagevimab 300 mg plus cilgavimab 300 mg as their initial dose. For patients who initially received tixagevimab 150 mg plus cilgavimab 150 mg >3 months ago, the simulations suggest that a repeat dose of tixagevimab 300 mg plus cilgavimab 300 mg is necessary.
- Observational data reported after the emergence of the Omicron variant suggested an association between the receipt of tixagevimab plus cilgavimab and a decreased incidence of COVID-19, although these studies were not definitive.25,26
- Safety data on the use of tixagevimab 300 mg plus cilgavimab 300 mg primarily come from TACKLE, a Phase 3 clinical trial that evaluated single doses of tixagevimab plus cilgavimab for the treatment of patients with mild to moderate COVID-19.24
Factoring in the limitations outlined above:
- The Panel recommends using tixagevimab 300 mg plus cilgavimab 300 mg administered as 2 consecutive 3-mL intramuscular (IM) injections (BIIb) as SARS-CoV-2 PrEP for adults and adolescents (aged ≥12 years and weighing ≥40 kg) who do not have SARS-CoV-2 infection, who have not been recently exposed to an individual with SARS-CoV-2 infection, AND who:
- Are moderately to severely immunocompromised and may have an inadequate immune response to COVID-19 vaccination; or
- Are not able to be fully vaccinated with any available COVID-19 vaccines due to a history of severe adverse reactions to a COVID-19 vaccine or any of its components.
- The Panel recommends repeat dosing of tixagevimab 300 mg plus cilgavimab 300 mg administered as IM injections every 6 months (BIIb), as allowed by the most recent revision of the FDA EUA. Repeat doses should be timed from the most recent dose of tixagevimab plus cilgavimab.
- The FDA EUA states that individuals who received tixagevimab 150 mg plus cilgavimab 150 mg should be given a second dose as soon as possible.
- If the initial dose was administered ≤3 months prior, the second dose should be tixagevimab 150 mg plus cilgavimab 150 mg.
- If the initial dose was administered >3 months prior, the second dose should be tixagevimab 300 mg plus cilgavimab 300 mg.
- Tixagevimab plus cilgavimab is not a substitute for COVID-19 vaccination and should not be used in unvaccinated individuals for whom COVID-19 vaccination is recommended.
- Evusheld contains the ingredient polysorbate 80, which is structurally related to polyethylene glycol.20 COVID-19 vaccines approved or authorized by the FDA contain either polysorbate 80 or polyethylene glycol. There is a theoretical risk of cross-hypersensitivity between Evusheld and COVID-19 vaccines. Before administering Evusheld to individuals with a history of severe hypersensitivity reactions to a COVID-19 vaccine, consultation with an allergist/immunologist should be considered.
- Individuals who qualify as having moderate to severe immunocompromising conditions under the FDA EUA for tixagevimab plus cilgavimab are those who:
- Are receiving active treatment for solid tumors and hematologic malignancies.
- Received a solid organ transplant and are receiving immunosuppressive therapy.
- Received chimeric antigen receptor T cell therapy or a hematopoietic stem cell transplant (and are within 2 years of transplantation or are receiving immunosuppressive therapy).
- Have a moderate or severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome).
- Have advanced or untreated HIV infection (defined as people with HIV and CD4 T lymphocyte cell counts <200 cells/mm3, a history of an AIDS-defining illness without immune reconstitution, or clinical manifestations of symptomatic HIV).
- Are receiving active treatment with high-dose corticosteroids (i.e., ≥20 mg prednisone or equivalent per day when administered for ≥2 weeks), alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive, tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (e.g., B cell-depleting agents).
- The strength of the Panel’s recommendation for tixagevimab 300 mg plus cilgavimab 300 mg is based partly on PK/PD modeling for the Omicron BA.1 and BA.1.1 subvariants and partly on the fact that the BA.2 subvariant has been shown to retain near-full susceptibility to tixagevimab plus cilgavimab in vitro.27
- Because no clinical trial efficacy data are available for tixagevimab 300 mg plus cilgavimab 300 mg, and there are uncertainties about the extent and duration of protection against the dominant circulating Omicron subvariants, high-risk individuals who receive PrEP should continue to use other measures to protect themselves from infection.
- If supplies of tixagevimab plus cilgavimab are limited, priority for use as PrEP should be given to those who are at the highest risk for severe COVID-19.
- If a person has received a COVID-19 vaccine, tixagevimab plus cilgavimab should be administered at least 2 weeks after vaccination.
- There is insufficient evidence for the Panel to recommend either for or against the use of SARS-CoV-2 serologic testing to assess for immunity or to guide clinical decisions about using anti-SARS-CoV-2 mAbs as PrEP. See Testing for SARS-CoV-2 Infection for more information.
Clinical Trial Data for Tixagevimab Plus Cilgavimab
PROVENT is an ongoing, Phase 3, double-blind, randomized, placebo-controlled trial that evaluated the use of tixagevimab plus cilgavimab for SARS-CoV-2 PrEP.19,20 The study enrolled adults aged ≥18 years who had not received a COVID-19 vaccine and who were at increased risk of severe SARS-CoV-2 infection (e.g., those aged ≥60 years or those who had a prespecified comorbidity) or who had an increased risk of acquiring SARS-CoV-2 infection due to their occupation or living situation. The study excluded those with a history of confirmed SARS-CoV-2 infection or who had a positive SARS-CoV-2 antibody result at screening.
The analyzed population included participants who received a negative reverse transcription polymerase chain reaction (RT-PCR) result at baseline. Participants received either tixagevimab 150 mg plus cilgavimab 150 mg (administered as 2 consecutive IM injections; n = 3,460) or placebo (administered as 2 IM injections; n = 1,737). The primary endpoint was symptomatic SARS-CoV-2 infection and a positive RT-PCR result during the 183 days of follow-up.
Once COVID-19 vaccines became available, participants could choose to be unblinded and receive the vaccine during the study. Only the primary endpoints that occurred prior to unblinding or vaccine receipt were included in the analysis, resulting in a median follow-up of 83 days. Baseline characteristics were well balanced between the arms. Prior to unblinding or vaccination, RT-PCR-confirmed symptomatic SARS-CoV-2 infection was reported for 8 participants (0.2%) in the tixagevimab plus cilgavimab arm and 17 participants (1.0%) in the placebo arm, representing a 77% reduction in the incidence of infection in the tixagevimab plus cilgavimab arm (95% CI, 46% to 90%; P < 0.001). A post hoc analysis after a median follow-up period of 6 months showed a relative risk reduction of 82.8% (95% CI, 65.8% to 91.4%) for symptomatic infection in the tixagevimab plus cilgavimab arm. Five cases of COVID-19 were considered to be severe or critical, and 2 COVID-19-related deaths were reported. All of these events occurred in participants who received placebo.
Adverse events were reported for 35.3% of participants in the tixagevimab plus cilgavimab arm and 34.2% of participants in the placebo arm. Serious adverse events were reported for 1% of participants in each arm; 1 participant in the tixagevimab plus cilgavimab arm had an anaphylactic reaction that was resolved with epinephrine therapy. The incidence of adverse events was similar in both study arms; most events were mild (62%) or moderate (32%). Rare, serious cardiac adverse events occurred in 0.7% of participants in the tixagevimab plus cilgavimab arm and in 0.3% of participants in the placebo arm. All participants who experienced a cardiac event had cardiac risk factors or a history of cardiac disease at baseline. There was no clear temporal pattern between these serious cardiac adverse events and administration of the anti-SARS-CoV-2 mAbs.20
TACKLE was a Phase 3 trial that evaluated the use of tixagevimab plus cilgavimab for the treatment of nonhospitalized patients with mild to moderate COVID-19. In this study, 452 high-risk adults aged ≥18 years received a single IM dose of tixagevimab 300 mg plus cilgavimab 300 mg and had a follow-up visit within 183 days (the median follow-up period was 84 days). Adverse events were reported for 29% of patients in the tixagevimab plus cilgavimab arm and for 36% of patients in the placebo arm; the majority of events were mild to moderate in severity. Serious cardiac adverse events were reported for 4 patients; 3 had received tixagevimab plus cilgavimab and 1 had received placebo. All events occurred in patients who had cardiac risk factors or a history of cardiovascular disease.20
Other Drugs for Pre-Exposure Prophylaxis
- The Panel recommends against the use of any oral drugs for SARS-CoV-2 PrEP, except in a clinical trial (AIII).
Clinical trials are investigating several agents, including emtricitabine plus tenofovir alafenamide or tenofovir disoproxil fumarate; hydroxychloroquine; ivermectin; and supplements such as zinc, vitamin C, and vitamin D. Please see ClinicalTrials.gov for the latest information.
Hydroxychloroquine, given at different doses and durations, has been studied in randomized controlled trials to assess whether it could prevent SARS-CoV-2 infection in those at risk of being exposed to infected individuals, such as health care workers. One study reported no evidence of a benefit of hydroxychloroquine, and it was ultimately halted due to futility before it reached its target enrollment.28 In another hydroxychloroquine study, which also did not meet its target enrollment and was stopped early, the majority of the potential transmission events were not confirmed by virologic testing.29 Neither study demonstrated any evidence of a reduction in the rate of acquiring infection. Both studies reported an increased frequency of mild adverse events in the treatment group.
Anti-SARS-CoV-2 Monoclonal Antibodies
- The Panel recommends against the use of bamlanivimab plus etesevimab and casirivimab plus imdevimab for post-exposure prophylaxis (PEP), as the Omicron variant and its subvariants, which are not susceptible to these agents, are currently the dominant SARS-CoV-2 variants circulating in the United States (AIII).
Vaccination remains a highly effective way to prevent SARS-CoV-2 infection. However, despite the widespread availability of COVID-19 vaccines, some individuals are not fully vaccinated or cannot mount an adequate response to the vaccine. Some of these individuals, if infected, are at high risk of progressing to serious COVID-19. Bamlanivimab plus etesevimab and casirivimab plus imdevimab have previously received FDA EUAs for PEP; however, the Omicron variant and its subvariants are currently the dominant SARS-CoV-2 variants circulating in the United States. The Panel recommends against the use of these anti-SARS-CoV-2 mAbs because the Omicron variant and its subvariants are not susceptible to them (AIII).
Chloroquine and Hydroxychloroquine
- The Panel recommends against the use of hydroxychloroquine for SARS-CoV-2 PEP (AI).
Both chloroquine and hydroxychloroquine have in vitro activity against SARS-CoV and SARS-CoV-2.30,31 A small cohort study without a control group suggested that hydroxychloroquine might reduce the risk of SARS-CoV-2 transmission to close contacts.32 There have been several large trials to determine whether hydroxychloroquine can reduce the risk of infection after exposure to individuals infected with SARS-CoV-2. These studies used different dose schedules and targeted different at-risk populations. In addition, some studies were unable to confirm infection using molecular or antigen tests. None of these studies demonstrated any evidence of efficacy for hydroxychloroquine, and all showed a higher risk of generally mild adverse events in those who received the drug.33-35
Other Drugs for Post-Exposure Prophylaxis
- The Panel recommends against the use of other drugs for SARS-CoV-2 PEP, except in a clinical trial (AIII).
A number of other agents (e.g., ivermectin, hyperimmune gamma globulin, COVID-19 convalescent plasma, interferons, tenofovir with or without emtricitabine, vitamin D) are currently being investigated for SARS-CoV-2 PEP. The latest clinical trials for SARS-CoV-2 PEP can be found at ClinicalTrials.gov.
High concentrations of ivermectin have been shown to inhibit SARS-CoV-2 replication in vitro.36,37 Population data indicated that countrywide, mass-use of prophylactic chemotherapy for parasitic infections, including the use of ivermectin, was associated with a lower incidence of COVID-19.38 At this time, few clinical trials have evaluated the safety and efficacy of using ivermectin for SARS-CoV-2 PrEP or PEP.36,37
In a descriptive, uncontrolled, interventional study of 33 contacts of patients with laboratory-confirmed SARS-CoV-2 infection, no cases of SARS-CoV-2 infection were identified within 21 days of initiating ivermectin for PEP.39 In a small case-control study in SARS-CoV-2-exposed health care workers, 186 participants who became infected were matched with 186 uninfected controls. Of those who received ivermectin after exposure to SARS-CoV-2, 38 were in the infected group and 77 were in the uninfected group, which led the investigators to conclude that ivermectin reduced the incidence of SARS-CoV-2 infection.40
- Centers for Disease Control and Prevention. Scientific brief: SARS-CoV-2 transmission. 2021. Available at: https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/sars-cov-2-transmission.html. Accessed June 21, 2022.
- Centers for Disease Control and Prevention. How to protect yourself and others. 2022. Available at: https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html. Accessed June 21, 2022.
- Centers for Disease Control and Prevention. Infection control guidance for healthcare professionals about coronavirus (COVID-19). 2020. Available at: https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-control.html. Accessed June 21, 2022.
- Centers for Disease Control and Prevention. Johnson & Johnson’s Janssen COVID-19 vaccine: overview and safety. 2022. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/janssen.html. Accessed June 21, 2022.
- Centers for Disease Control and Prevention. Use of COVID-19 vaccines in the United States: interim clinical considerations. 2022. Available at: https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html. Accessed June 21, 2022.
- Centers for Disease Control and Prevention. Interim considerations: preparing for the potential management of anaphylaxis after COVID-19 vaccination. 2022. Available at: https://www.cdc.gov/vaccines/covid-19/clinical-considerations/managing-anaphylaxis.html. Accessed June 21, 2022.
- Food and Drug Administration. Fact sheet for healthcare providers administering vaccine (vaccination providers): emergency use authorization (EUA) of the Janssen COVID-19 vaccine to prevent coronavirus disease 2019 (COVID-19). 2022. Available at: https://www.fda.gov/media/146304/download.
- See I, Lale A, Marquez P, et al. Case series of thrombosis with thrombocytopenia syndrome after COVID-19 vaccination—United States, December 2020 to August 2021. Ann Intern Med. 2022;175(4):513-522. Available at: https://www.ncbi.nlm.nih.gov/pubmed/35038274.
- American Society of Hematology. Vaccine-induced immune thrombotic thrombocytopenia. 2022. Available at: https://www.hematology.org/covid-19/vaccine-induced-immune-thrombotic-thrombocytopenia. Accessed June 21, 2022.
- Furie KL, Cushman M, Elkind MSV, et al. Diagnosis and management of cerebral venous sinus thrombosis with vaccine-induced immune thrombotic thrombocytopenia. Stroke. 2021;52(7):2478-2482. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33914590.
- Centers for Disease Control and Prevention. Selected adverse events reported after COVID-19 vaccination. 2022. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html. Accessed June 21, 2022.
- Centers for Disease Control and Prevention. COVID-19 vaccines while pregnant or breastfeeding. 2022. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html. Accessed June 21, 2022.
- Society for Maternal-Fetal Medicine. Publications and clinical guidance. 2022. Available at: https://www.smfm.org/covidclinical. Accessed June 21, 2022.
- Shimabukuro TT, Kim SY, Myers TR, et al. Preliminary findings of mRNA COVID-19 vaccine safety in pregnant persons. N Engl J Med. 2021;384(24):2273-2282. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33882218.
- Zauche LH, Wallace B, Smoots AN, et al. Receipt of mRNA COVID-19 vaccines and risk of spontaneous abortion. N Engl J Med. 2021;385(16):1533-1535. Available at: https://www.ncbi.nlm.nih.gov/pubmed/34496196.
- Goldshtein I, Nevo D, Steinberg DM, et al. Association between BNT162b2 vaccination and incidence of SARS-CoV-2 infection in pregnant women. JAMA. 2021;326(8):728-735. Available at: https://www.ncbi.nlm.nih.gov/pubmed/34251417.
- Collier AY, McMahan K, Yu J, et al. Immunogenicity of COVID-19 mRNA vaccines in pregnant and lactating women. JAMA. 2021;325(23):2370-2380. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33983379.
- American College of Obstetricians and Gynecologists. Practice advisory: COVID-19 vaccination considerations for obstetric-gynecologic care. 2022. Available at: https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2020/12/vaccinating-pregnant-and-lactating-patients-against-covid-19. Accessed June 21, 2022.
- Levin MJ, Ustianowski A, De Wit S, et al. Intramuscular AZD7442 (tixagevimab-cilgavimab) for prevention of COVID-19. N Engl J Med. 2022;386(23):2188-2200. Available at: https://www.ncbi.nlm.nih.gov/pubmed/35443106.
- Food and Drug Administration. Fact sheet for healthcare providers: emergency use authorization for Evusheld (tixagevimab co-packaged with cilgavimab). 2022. Available at: https://www.fda.gov/media/154701/download.
- Cameroni E, Bowen JE, Rosen LE, et al. Broadly neutralizing antibodies overcome SARS-CoV-2 Omicron antigenic shift. Nature. 2022;602(7898):664-670. Available at: https://www.ncbi.nlm.nih.gov/pubmed/35016195.
- Takashita E, Kinoshita N, Yamayoshi S, et al. Efficacy of antibodies and antiviral drugs against COVID-19 Omicron variant. N Engl J Med. 2022;386(10):995-998. Available at: https://www.ncbi.nlm.nih.gov/pubmed/35081300.
- Iketani S, Liu L, Guo Y, et al. Antibody evasion properties of SARS-CoV-2 Omicron sublineages. Nature. 2022;604(7906):553-556. Available at: https://www.ncbi.nlm.nih.gov/pubmed/35240676.
- Food and Drug Administration. Emergency Use Authorization (EUA) for Evusheld. 2022. Available at: https://www.fda.gov/media/156674/download.
- Young-Xu Y, Epstein L, Marconi VC, et al. Tixagevimab/cilgavimab for prevention of COVID-19 during the Omicron surge: retrospective analysis of national VA electronic data. medRxiv. 2022;Preprint. Available at: https://www.medrxiv.org/content/10.1101/2022.05.28.22275716v1.
- Al Jurdi A, Morena L, Cote M, et al. Tixagevimab/cilgavimab pre-exposure prophylaxis is associated with lower breakthrough infection risk in vaccinated solid organ transplant recipients during the Omicron wave. Am J Transplant. 2022;Published online ahead of print. Available at: https://www.ncbi.nlm.nih.gov/pubmed/35727916.
- Food and Drug Administration. Emergency Use Authorization (EUA) for Evusheld: Center for Drug Evaluation and Research review memorandum. 2022. Available at: https://www.fda.gov/media/157371/download.
- Abella BS, Jolkovsky EL, Biney BT, et al. Efficacy and safety of hydroxychloroquine vs placebo for pre-exposure SARS-CoV-2 prophylaxis among health care workers: a randomized clinical trial. JAMA Intern Med. 2021;181(2):195-202. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33001138.
- Rajasingham R, Bangdiwala AS, Nicol MR, et al. Hydroxychloroquine as pre-exposure prophylaxis for coronavirus disease 2019 (COVID-19) in healthcare workers: a randomized trial. Clin Infect Dis. 2021;72(11):e835-e843. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33068425.
- Yao X, Ye F, Zhang M, et al. In vitro antiviral activity and projection of optimized dosing design of hydroxychloroquine for the treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Clin Infect Dis. 2020;71(15):732-739. Available at: https://www.ncbi.nlm.nih.gov/pubmed/32150618.
- Vincent MJ, Bergeron E, Benjannet S, et al. Chloroquine is a potent inhibitor of SARS coronavirus infection and spread. Virol J. 2005;2:69. Available at: https://www.ncbi.nlm.nih.gov/pubmed/16115318.
- Lee SH, Son H, Peck KR. Can post-exposure prophylaxis for COVID-19 be considered as an outbreak response strategy in long-term care hospitals? Int J Antimicrob Agents. 2020;55(6):105988. Available at: https://www.ncbi.nlm.nih.gov/pubmed/32305587.
- Barnabas RV, Brown ER, Bershteyn A, et al. Hydroxychloroquine as postexposure prophylaxis to prevent severe acute respiratory syndrome coronavirus 2 infection: a randomized trial. Ann Intern Med. 2021;174(3):344-352. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33284679.
- Boulware DR, Pullen MF, Bangdiwala AS, et al. A randomized trial of hydroxychloroquine as postexposure prophylaxis for COVID-19. N Engl J Med. 2020;383(6):517-525. Available at: https://www.ncbi.nlm.nih.gov/pubmed/32492293.
- Mitja O, Corbacho-Monne M, Ubals M, et al. A cluster-randomized trial of hydroxychloroquine for prevention of COVID-19. N Engl J Med. 2021;384(5):417-427. Available at: https://www.ncbi.nlm.nih.gov/pubmed/33289973.
- Caly L, Druce JD, Catton MG, Jans DA, Wagstaff KM. The FDA-approved drug ivermectin inhibits the replication of SARS-CoV-2 in vitro. Antiviral Res. 2020;178:104787. Available at: https://www.ncbi.nlm.nih.gov/pubmed/32251768.
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