On March 11, 2020, the World Health Organization (WHO) declared a global pandemic of a novel respiratory coronavirus, now known as SARS-CoV-2.1 Rapid spread of the original virus and its multiple variants led to more than 1 million deaths in the United States and nearly 7 million deaths worldwide by the time the WHO declared an end to the global health emergency on May 5, 2023.1,2 In the United States, the national public health emergency began on January 31, 2020, and ended on May 11, 2023.

The toll of illness and death taken by COVID-19 would have been far worse had it not been for the fast-track development of vaccines, which first became available in December 2020, less than 1 year into the pandemic. A modeling study by The Commonwealth Fund reported that, through November 2022, vaccines had prevented an estimated 18.5 million additional hospitalizations and 3.2 million deaths in the United States while saving $1.15 trillion in health care costs. “Without vaccination,” the authors concluded, “the US would have experienced 1.5 times more infections, 3.8 times more hospitalizations, and 4.1 times more deaths.”3

Although the emergency has officially ended, COVID-19 remains a health threat. Vaccination of individuals at risk continues to be a public health priority.


The first cases of COVID-19 were reported in December 2019 in Wuhan, China. The origins of the virus are a matter of ongoing scientific and political debate. The most likely explanations are natural emergence from an animal source (zoonotic spillover) or an accidental leak of the virus from a laboratory in Wuhan.4

People at Risk

Older adults are at high risk for severe illness and death from COVID-19; more than 80% of COVID-19 deaths have occurred in people aged 60 and older.5

Also at increased risk are people with underlying medical conditions, including cancer, chronic kidney disease, chronic lung disease, dementia, type 1 or 2 diabetes, Down syndrome, heart disease, HIV infection, liver disease, and sickle cell disease. Additional high-risk groups include residents of nursing homes or other long-term care facilities; obese individuals (ie, those with a body mass index greater than 30); pregnant women; smokers, and people with a weakened immune system.6,7

Outside of these high-risk groups, COVID-19 may cause only mild symptoms.


The SARS-CoV-2 virus spreads through respiratory droplets via coughing, sneezing, or talking. An infected person may transmit the virus even if not symptomatic.


Symptoms of COVID-19 typically develop 2 to 14 days after infection and include fever, cough, and shortness of breath or difficulty breathing. The range of symptoms is wide and may also include chills, fatigue, muscle pain or body aches, headache, sore throat, new loss of taste or smell, congestion or runny nose, nausea or vomiting, and diarrhea. Many symptoms of COVID-19 infection are similar to those of a cold, influenza, or other respiratory illnesses.2,7

Some children develop a multisystem inflammatory syndrome (MIS-C) after becoming infected with the SARS-CoV-2 virus. Inflammation may affect the heart, lungs, brain, kidneys, gastrointestinal tract, skin, and eyes. Most children will recover with medical care but some cases prove fatal.


Molecular tests, also known as PCR tests, detect genetic material of the SARS-CoV-2 virus. These tests are ordered by a health care professional.

Antigen tests are rapid tests that can be performed at home with nasal swabs and provide results within 10 minutes. Antigen tests detect viral fragments but are not as sensitive as molecular tests.

Antibody tests detect the body’s immune response to the virus. They can identify people who have been infected but should not be used to diagnose a current infection.


US Food and Drug Administration (FDA)-approved drugs for treating COVID-19 include:

  • Paxlovid, which consists of two oral antiviral agents (nirmatrelvir and ritonavir) packaged together, is approved for treatment of mild to moderate COVID-19 in adults at high risk of progression to severe disease, including hospitalization or death. Treatment should begin as soon as possible after diagnosis and within 5 days of symptom onset.
  • Veklury (remdesivir), is an antiviral approved for treating COVID-19 in adult and pediatric patients (at least 28 days of age and weighing at least 3 kg) who are hospitalized, or not hospitalized but have mild to moderate COVID-19 and are at high risk for progression to severe disease, including hospitalization and death. Remdesivir is an intravenous injection.
  • Actemra (tocilizumab) is an interleukin-6 (IL-6) receptor antagonist, administered by intravenous infusion. It is approved for treating COVID-19 in hospitalized adults who are receiving systemic corticosteroids and require supplemental oxygen, invasive or non-invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO).
  • Olumiant (baricitinib) is an oral Janus kinase (JAK) inhibitor approved for treating COVID-19 in hospitalized adults who require supplemental oxygen, invasive or non-invasive mechanical ventilation or ECMO. 

The following drugs have emergency use authorization from the FDA for treating patients with COVID-19:

  • Lagevrio (molnupiravir), an oral nucleoside analog, is authorized for treating people with mild to moderate COVID-19 at risk of progression to severe disease, and for whom alternative treatment options are not accessible or clinically appropriate.
  • Gohibic (vilobelimab) is an intravenous infusion authorized for treating COVID-19 in hospitalized adults when initiated within 48 hours of receiving invasive mechanical ventilation or ECMO.


  • Pfizer-BioNTech COVID-19 vaccine, bivalent, and Moderna COVID-19 vaccine, bivalent, are now authorized for all doses administered to people 6 months of age and older. These bivalent mRNA vaccines are also known as “updated” vaccines as they protect against the original SARS-CoV-2 virus as well as Omicron variants BA.4 and BA.5.
  • Recommended doses of COVID-19 vaccine vary according to the age of the individual and the number of doses and type of vaccine received previously. The CDC has published a detailed table outlining its recommendations by age group, vaccine history, and immune status.
  • As of April 18, 2023, the monovalent Pfizer-BioNTech and Moderna COVID-19 vaccines are no longer authorized for use in the United States.
  • The CDC says that everyone 6 years of age and older who receives 1 dose of the “updated” Pfizer/BioNTech or Moderna vaccine is considered up to date on COVID-19 immunization[FH1] .
  • People 65 and older may receive 1 additional dose of updated vaccine at least 4 months after the first updated dose.
  • Most individuals who are moderately or severely immunocompromised may receive 1 additional dose of updated vaccine at least 2 months after the first updated dose, with additional doses and their timing to be determined by the healthcare provider.
  • Novavax COVID-19 vaccine, adjuvanted, is authorized to provide a 2-dose primary series, with 3 weeks between doses, to individuals 12 years of age and older. It is also authorized for use as a first booster dose at least 6 months after completing primary vaccination with an authorized or approved COVID-19 vaccine. In those situations, Novavax is an alternative for people who do not wish to receive an mRNA bivalent vaccine or those for whom the mRNA vaccines are not accessible or clinically appropriate.
  • As of May 7, 2023, the J&J (Janssen) COVID-19 vaccine is no longer available in the United States. The CDC recommends that anyone who received 1 or 2 doses of the Janssen vaccine receive a dose of the bivalent Pfizer-BioNTech or Moderna vaccine at least 2 months after completing the previous dose.

Long COVID or Post COVID Conditions

Infection with the SARS-CoV-2 virus can cause signs, symptoms, and conditions that may persist for weeks, months, or years.Known as long COVID or Post-COVID Conditions, these lingering health issues can occur in anyone who has been infected with the virus but is more likely to occur in people who have had severe illness. People who were not vaccinated against SARS-CoV-2 prior to becoming infected may also be at higher risk of long COVID.2,10

Long COVID is estimated to occur in at least 10% of SARS-CoV-2 infections, with more than 200 symptoms identified throughout multiple organ systems.Worldwide, an estimated 65 million people are living with long COVID with numbers increasing daily.10  


  1. World Health Organization. Coronavirus disease (COVID-19) pandemic. Accessed June 19, 2023.
  2. Centers for Disease Control and Prevention (CDC). COVID-19. Accessed June 19, 2023.
  3. Fitzpatrick MC, Moghadas SM, Pandey A, Galvani AP. Two years of U.S. COVID-19 vaccines have prevented millions of hospitalizations and deaths. Published December 13, 2022. Accessed June 11, 2023. https://www.
  4. Gostin LO, Gronvall GK. The origins of Covid-19—why it matters (and why it doesn’t). N Engl J Med. 2023;388(25):2305-2308. doi:10.1056/NEJMp2305081
  5. Wong MK, Brooks DJ, Ikejezie J, et al. COVID-19 mortality and progress toward vaccinating older adults—World Health Organization, Worldwide, 2020-2022. MMWR. 2023;72(5):113-118. doi:10.15585/mmwr.mm7205a1
  6. CDC. COVID-19. People with certain medical conditions. Updated May 11, 2023. Accessed June 19, 2023.
  7. National Foundation for Infectious Diseases. 2019 novel coronavirus (COVID-19) pandemic. Accessed June 19, 2023.
  8. CDC. Stay up to date with COVID-19 vaccines. Updated June 7, 2023. Accessed June 19, 2023.
  9. Rosenblum HG, Wallace M, Godfrey M, et al. Interim recommendations from the Advisory Committee on Immunization Practices for the use of booster doses of COVID-19 vaccines—United States, October 2022. MMWR. 2022;71(45):1436-1441. doi:10.15585/mmwr.mm7145a2
  10. Evans HE, McCorkell L, Vogel JM, Topol EJ. Long COVID: major findings, mechanisms and recommendations. Nat Rev Microbiol. 2023;21(3):133-146. doi:10.1038/s41579-022-00846-2