The SARS-CoV-2 virus
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SARS-CoV-2, the novel coronavirus that causes the pneumonia-like illness COVID-19, emerged at the end of 2019. The virus spread at an alarming rate, prompting the World Health Organization to declare the outbreak a pandemic and the U.S. Department of Health and Human Services to declare a public health emergency. Use these resources to help understand COVID-19 and be proactive about prevention.

COVID-19 News and Spotlights

FDA Authorizes Pfizer-BioNTech COVID-19 Vaccine Boosters for Certain People

September 23, 2021

The U.S. Food and Drug Administration (FDA) has authorized booster doses of the Pfizer-BioNTech COVID-19 vaccine for certain people. The boosters can be given 6 months or more after the initial series of the vaccine. Based on available scientific evidence, the FDA has determined that the booster doses may be effective in preventing COVID-19, and that the benefits from these boosters outweigh any possible risks in the people for whom the boosters are authorized. 

The booster doses are authorized for people:

  • Age 65 and older
  • Age 18 through 64 at high risk of severe COVID-19
  • Age 18 through 64 whose potentially frequent exposure to the virus that causes COVID-19 puts them at risk of serious illness. A few examples include health care workers, first responders, teachers, day care staff, grocery workers, and those in homeless shelters or prisons.

“This pandemic is dynamic and evolving, with new data about vaccine safety and effectiveness becoming available every day,” Acting FDA Commissioner Janet Woodcock, M.D. said in a press release. “As we learn more about the safety and effectiveness of COVID-19 vaccines, including the use of a booster dose, we will continue to evaluate the rapidly changing science and keep the public informed.”

 The following table summarizes the three vaccines currently available in the U.S.

Vaccine features Pfizer-BioNTech Moderna Jansen/Johnson & Johnson
Effectiveness 91% in those age 16+; more than 89% in people with underlying conditions; 100% in children age 12 to 15 94%, more than 90% in people with underlying conditions 66% in preventing COVID-19 with symptoms; 85% in preventing severe illness
Ages approved Age 12+ Age 18+ Age 18*
Number of doses 2 doses 21 days apart 2 doses, 28 days apart 1 dose
Booster authorized 6 months after initial vaccine series for those age 65+ and people at risk of serious disease No No
Most common side effects Pain at the injection site, headache, fatigue, muscle pain, chills
How they work While these different vaccines work slightly differently, they all prompt our immune systems to produce white blood cells that fight the virus. Building this immunity can sometimes cause symptoms. Our bodies keep some “memory” white blood cells so that the next time we are exposed to the virus, our immune system will remember how to fight it. For details, read the CDC’s Understanding How COVID-19 Vaccines Work


U.S. Food and Drug Administration Press Release. (September 22, 2021). FDA Authorizes Booster Dose of Pfizer-BioNTech COVID-19 Vaccine for Certain Populations. Accessed 9/23/2021

Centers for Disease Control and Prevention. (Updated September 1, 2021) Different COVID-19 Vaccines. Accessed September 23, 2021

© 2021 Mayo Clinic, Comparing the differences between COVID-19 vaccines. Accessed September 23, 2021

U.S. Grappling with Shortage of COVID-19 Tests Again

September 2, 2021

As the number of COVID-19 cases in the U.S. resurge during late summer into the fall, major diagnostic manufacturers are reporting a shortage of tests again, according to a Reuters news report. As a result, some people may have a harder time finding a COVID-19 test, or may have to wait longer than expected to get tested. 

Early in the pandemic, COVID-19 tests were in short supply, but companies and laboratories worked to increase the availability of tests that could quickly and accurately diagnose an active infection with SARS-CoV-2, the virus that causes COVID-19. Through emergency-use authorizations (EUAs) from the FDA, various tests came on the market or were available from labs, including PCR (molecular) tests that detect viral genetic material and antigen tests that detect viral proteins. Some tests performed at labs can provide results within 2 to 3 days, while other rapid tests can give results within several minutes. The last few months, these tests have been widely available through doctors’ offices, clinics and drugstores, and some have been available over-the-counter in stores or online. 

With the drop in cases during early summer months, however, manufacturers began to scale back on the number of tests they produced. Some companies shut down COVID-19 test production lines, or shifted to manufacturing other types of medical tests.    

Now with a resurgence in COVID-19 cases spurred by the more contagious delta variant, demand for COVID-19 testing is rebounding. Even those who are fully vaccinated are encouraged to get tested if they have symptoms or have been in close contact with someone diagnosed with the infection. Moreover, the need for COVID-19 testing is expected to continue to grow into the fall and winter as schools, colleges and workplaces require some people to undergo regular testing–as often as once per week.

As demand outpaces supply, companies are once again ramping up test production. Though quantities are limited currently, manufacturers predict test stockpiles to improve in the next couple of weeks.    


Carl O’Donnell (August 27, 2021) U.S. COVID-19 tests again in short supply as infections soar, schools reopen. Reuters. Accessed September 2, 2021

(August 27, 2021) COVID-19 Data Tracker Weekly Review, Centers for Disease Control and Prevention. Accessed September 2, 2021

(July 28, 2021) Centers for Disease Control and Prevention, Interim Public Health Recommendations for Fully Vaccinated People. Accessed September 2, 2021

Updated Guidance for Fully Vaccinated People: When to Wear a Mask and When to Get Tested

August 4, 2021

In light of the spike in COVID-19 cases in the U.S. in recent weeks, the Centers for Disease Control and Prevention have updated their guidance for people who are fully vaccinated. You are considered fully vaccinated two weeks after you have received the final dose of a vaccine. In the updated information published July 27, 2021, the agency notes that people who are fully vaccinated can resume many of the activities they took part in pre-pandemic. However, extra precautions are recommended now that case counts are increasing. 

Among the recommendations for masks:

  • Wear a mask indoors in public places if you are in an area of the U.S. where there is high or substantial transmission of the virus (SARS-CoV-2). As of August 4, 2021, this includes much of the country.
  • Some fully vaccinated people may opt to wear a mask even in areas of lower transmission, especially if they or someone they live with is at higher risk of infection or severe disease.
  • Wear a mask indoors in public places if you come into close contact with someone who has COVID-19, regardless of where you live, and get tested (see below). Close contact means being within 6 feet of someone with COVID-19 for 15 minutes or more over a 24 hour period. Wear the mask for 14 days or until you get a negative test result. 
  • All students, teachers, staff and visitors to schools are recommended to wear masks regardless of whether they have been vaccinated or not.

Among the recommendations for testing:

  • Get tested if you have symptoms of COVID-19, such as
    • Cough, runny nose, congestion
    • Sore throat
    • Headache
    • Fatigue
    • Fever, chills
    • Muscle and body aches
    • Loss of taste or smell
  • Get tested 3 to 5 days after exposure if you come into close contact with someone who has COVID-19. As mentioned above, take precautions like wearing a mask unless and until you get a negative result.
  • If the result of your test is negative, you can resume usual activities, following the guidelines.
  • Isolate if you have a positive test result or have symptoms of COVID-19.

Source: (July 28, 2021) Centers for Disease Control and Prevention, Interim Public Health Recommendations for Fully Vaccinated People. Accessed August 4, 2021

CDC COVID-19 Self-Checker

Answer questions to help you decide whether to seek medical care and get tested. To get started, click the button below: