It’s been five years since theCOVID-19 pandemicbegan—and a lot has changed.

“We opened up the book to COVID five years ago, and the pages were blank. The pages are now filled,” saidWilliam Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine.

Here’s what we know—and still don’t know—about COVID.

15 Common Coronavirus (COVID-19) Questions

What We Know About COVID-19

It Can Spread a Few Different Ways

At first, there was uncertainty over how the virus spread. Many people wiped down their groceries and used hand sanitizer to avoid getting the virus from contaminated surfaces.

Data has shown that SARS-CoV-2, the virus that causes COVID-19, is most commonly spread through respiratory droplets and aerosols.

“This is clearly arespiratory virus, and it’s extraordinarily infectious,”Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo, told Verywell.

Certain People Are More at Risk Than Others

Early in the pandemic, everyone was at risk for developing severe disease from COVID, because they had never been exposed to the virus before, Russo said. While everyone is technically still at risk, data shows that some people are more vulnerable than others.

Those include very young children, older adults, and people with certain health conditions, such asdiabetes, asthma, or chronic lung disease.

Vaccines Have Made a Big Impact

The firstCOVID vaccineswere released in December 2020, just months after the pandemic began. “The vaccines are a scientific miracle,” Schaffner said. “They are effective and they are safe.”

Data show that mRNA vaccines are up to 96% effective when matched with the dominant circulating strain of COVID.

“Vaccines against respiratory viruses cannot prevent all mild infections, but they do provide good protection against developing serious illness—they will keep you out of the hospital and prevent you from dying,” Schaffner said.

The Virus—and Symptoms—Continues to Evolve

Today’s COVID is not the same as the original strain. “This is an RNA virus, and these viruses like to mutate,” Schaffner said. “Theinfluenza virusdoes the same thing.”

The virus has morphed to create several different strains.Omicron variantscontinue to dominate infections today. Symptoms of the virus have also changed slightly.

“There is now less loss of taste and smell,” Russo said. “The overall symptoms and severity of disease has lessened to a degree,” he added. There are also fewer lower respiratory tract symptoms, such asshortness of breathandchest pain.

For people who have been vaccinated or who previously had COVID, the virus may cause “morecold-like symptoms,” Russo said.

Immunity Wanes Over Time

Most people now have some degree ofimmunity to COVID, either from vaccination or infection, Schaffner said. The data on how long that immunity lasts varies, but some research suggests that it can last six months.

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What We Still Don’t Know About COVID

The Virus’ Origin

This is one of the bigger mysteries surrounding COVID. “There is constant debate about the origins—where did it come from? How did it start?” Schaffner said.

“Everyone wants to know about the origins, but I’m pretty certain that we’ll never figure that one out,” Russo said.

Why Some People Develop Long COVID

Research has not yet been able to pinpoint why some people developlong COVIDand others don’t. “The research into how the virus produces long COVID and how we can treat it is still very much ongoing,” Schaffner said.

Whether COVID Will Become Seasonal

Currently, COVID cases seem to experience peaks in the winter and summer, but they’re not always consistent. Unlike influenza, COVID cases continue to simmer all year. “It’s currently a year-round virus with peaks,” Russo said.

COVID-19 Treatments: What You Need to Know

What This Means For YOuA lot has happened since the COVID-19 pandemic began, but doctors have learned plenty of things about how the virus behaves, including how to prevent and treat it. Doctors stress that staying up to date on your COVID-19 vaccinations is the best way to protect yourself.

What This Means For YOu

A lot has happened since the COVID-19 pandemic began, but doctors have learned plenty of things about how the virus behaves, including how to prevent and treat it. Doctors stress that staying up to date on your COVID-19 vaccinations is the best way to protect yourself.

8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.About COVID-19.Centers for Disease Control and Prevention.People with certain medical conditions and COVID-19 risk factors.Food and Drug Administration.FDA approves first COVID-19 vaccine.Lin DY, Gu Y, Wheeler B, et al.Effectiveness of Covid-19 vaccines over a 9-month period in North Carolina.N Engl J Med. 2022;386(10):933-941. doi:10.1056/NEJMoa2117128Centers for Disease Control and Prevention.COVID data tracker.Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063Centers for Disease Control and Prevention.Animals and COVID-19.World Health Organization.WHO COVID-19 dashboard.

8 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.About COVID-19.Centers for Disease Control and Prevention.People with certain medical conditions and COVID-19 risk factors.Food and Drug Administration.FDA approves first COVID-19 vaccine.Lin DY, Gu Y, Wheeler B, et al.Effectiveness of Covid-19 vaccines over a 9-month period in North Carolina.N Engl J Med. 2022;386(10):933-941. doi:10.1056/NEJMoa2117128Centers for Disease Control and Prevention.COVID data tracker.Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063Centers for Disease Control and Prevention.Animals and COVID-19.World Health Organization.WHO COVID-19 dashboard.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Centers for Disease Control and Prevention.About COVID-19.Centers for Disease Control and Prevention.People with certain medical conditions and COVID-19 risk factors.Food and Drug Administration.FDA approves first COVID-19 vaccine.Lin DY, Gu Y, Wheeler B, et al.Effectiveness of Covid-19 vaccines over a 9-month period in North Carolina.N Engl J Med. 2022;386(10):933-941. doi:10.1056/NEJMoa2117128Centers for Disease Control and Prevention.COVID data tracker.Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063Centers for Disease Control and Prevention.Animals and COVID-19.World Health Organization.WHO COVID-19 dashboard.

Centers for Disease Control and Prevention.About COVID-19.

Centers for Disease Control and Prevention.People with certain medical conditions and COVID-19 risk factors.

Food and Drug Administration.FDA approves first COVID-19 vaccine.

Lin DY, Gu Y, Wheeler B, et al.Effectiveness of Covid-19 vaccines over a 9-month period in North Carolina.N Engl J Med. 2022;386(10):933-941. doi:10.1056/NEJMoa2117128

Centers for Disease Control and Prevention.COVID data tracker.

Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063

Centers for Disease Control and Prevention.Animals and COVID-19.

World Health Organization.WHO COVID-19 dashboard.

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