To combat the health crisis, countries around the globe have administered more than 8.5 billion doses of COVID-19 vaccine and drugmakers have developed new treatments.
Here are some of the key moments of the COVID-19 pandemic from the past two years:
DEC. 31 2019
The Wuhan Municipal Health Commission, China, reported a cluster of pneumonia cases in Wuhan, the capital city of the Hubei Province.
JANUARY 2020
The World Health Organization (WHO) said Chinese authorities have determined the outbreak was caused by a novel coronavirus. Soon after, Thailand reported the first confirmed case of the coronavirus outside China.
China on Jan. 23 announced a lockdown in Wuhan, and at month-end the WHO declared the coronavirus outbreak a "public health emergency of international concern."
FEBRUARY 2020
The WHO named the novel coronavirus SARS-COV2, an acronym for severe acute respiratory syndrome coronavirus 2. It named the disease caused by the virus as COVID-19, an abbreviation for Coronavirus Disease 2019.
MARCH 2020
The WHO described the coronavirus outbreak as a pandemic for the first time.
Italy's Lombardy region became the single deadliest coronavirus hotspot on the planet, with more than 3,000 deaths that eclipsed those in China's Hubei.
"The whole of Italy is closed now," read a headline in the Corriere della Sera newspaper after Rome imposed the most severe controls on a Western nation since World War II.
Several other countries, including Spain, France, Thailand, South Korea, Australia and Malaysia, also imposed lockdowns.
On March 13, the United States declared the pandemic a national emergency to free up $50 billion in federal aid. Later that month, California became the first U.S. state to issue a "stay-at-home order", while New York closed non-essential businesses.
India announced a nationwide lockdown on March 24, the same day when the 2020 Summer Olympics in Japan were postponed.
On March 27, British Prime Minister Boris Johnson tested positive for the coronavirus.
APRIL 2020
COVID-19 infections crossed 1 million and the WHO reported evidence that transmission from an infected person could occur before symptoms showed.
JULY 2020
On July 7, Brazilian President Jair Bolsonaro tested positive.
Later that month, Moderna and Pfizer launched large clinical trials of their respective COVID-19 shots.
SEPTEMBER 2020
Death toll from COVID-19 crossed 1 million, less than a year after the virus was discovered in China.
OCTOBER 2020
On Oct. 1, then-U.S. President Donald Trump tested positive for COVID-19, a little more than a month before the presidential election.
NOVEMBER 2020
Pfizer and German partner BioNTech said their experimental COVID-19 shot was more than 90% effective in preventing the disease, the first successful interim data on a COVID-19 vaccine from a large-scale clinical test.
Moderna Inc became the second U.S. company to demonstrate success of its COVID-19 vaccine, reporting that its shot was 94.5% effective in preventing the disease.
DECEMBER 2020
Britain approved Pfizer's COVID-19 vaccine for emergency use, making it the first country in the world to begin mass inoculations against the coronavirus.
On Dec. 11, the United States authorized the Pfizer-BioNTech shot for emergency use for people aged 16 and older as deaths from COVID-19 in the country neared 300,000.
New variants of the coronavirus were detected in Britain, South Africa and India. The WHO classified the variants from the UK and South Africa as variants of concern. It later named the strains Alpha and Beta.
JANUARY 2021
The WHO classified the P.1 variant, first found in Brazil in November 2020, as "variant of concern" following a surge in cases and deaths in the country. It was later named the Gamma variant.
March 2021
Brazil's most-populous state Sao Paulo announced a partial lockdown to combat surging infections, driven in part by a patchy vaccine rollouts.
MAY 2021
The WHO declared the B.1.617.2 variant, first detected in India, as "variant of concern" at a global level. The variant fuelled a second wave of infections in the country, driving daily cases above 300,000 and crippling India's healthcare infrastructure.
The WHO later named the variant as Delta.
JUNE 2021
Global COVID-19 related deaths crossed 4 million as the Delta variant became the dominant strain across the world.
JULY 2021
Israel the became first in the world to step up efforts against the Delta variant by rolling out booster shots of the Pfizer-BioNTech COVID-19 vaccine for those aged over 60.
AUGUST 2021
The U.S. FDA authorized a third dose of the Pfizer-BioNTech and Moderna COVID-19 vaccines for immunocompromised individuals.
SEPTEMBER 2021
U.S. regulators cleared booster shots of Pfizer's vaccine for those 65 and older, all people at high risk of severe disease and others who are regularly exposed to the virus.
OCTOBER 2021
The United States authorized Moderna vaccine boosters for some sections of its population and boosters from Johnson & Johnson for individuals 18 years and above. It also backed the use of a different shot from the original inoculation as a booster.
Worldwide COVID-19 deaths surpassed 5 million.
NOVEMBER 2021
On Nov.4, Britain became the first country in the world to approve an oral COVID-19 antiviral pill jointly developed by Merck & Co Inc and Ridgeback Biotherapeutics.
The United States expanded eligibility for booster shots to all adults, even as the WHO voiced concerns about equitable supply of shots globally.
A new COVID-19 variant, later termed Omicron, was detected in Hong Kong and southern Africa.
DECEMBER 2021
On Dec. 12, South African President Cyril Ramaphosa tested positive for COVID-19.
As of to date, the global coronavirus caseload has topped 284.4 million, while the deaths have surged to more than 5.42 million and vaccinations to over 9.07 billion, according to Johns Hopkins University.
