COVID-19 Breakthrough Infection in Fully Vaccinated People and in People Who Received a Booster Dose

A novel coronavirus, SARS-CoV-2 (formerly known as the 2019 novel coronavirus \[2019-nCoV\]) was identified as the agent that caused an outbreak of pneumonia (termed COVID-19) in Wuhan, China in December 2019. The virus quickly spread to other countries and on March 11, 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. By March 2021, many nations and organizations embarked on finding a cure or vaccine for this devastating viral infection. The Pfizer COVID-19 mRNA vaccine was the first to obtain emergency use authorization (EUA) from the Food \& Drug Administration (FDA) on December 11, 2020, followed by the Moderna COVID-19 mRNA vaccine on December 18, 2020, and the Janssen COVID-19 viral vector vaccine on February 27, 2021. The mRNA vaccines and the viral vector vaccine are designed based on the spike protein of SARS-COV-2. These vaccines had been administered to millions of Americans prior to July 2021.