On 22nd  September 2021, the United States Food and Drug Administration (US-FDA) modified  emergency use authorization (EUA) for the coronavirus vaccine to permit utilization of a single booster dose in specific populations:

• people aged 18-64 years at elevated risk of severe coronavirus infection
• people aged 65 years and older
• people 18-64 years of age whose frequent institutional or occupational exposure to coronavirus makes them more vulnerable to an elevated risk of severe complications of coronavirus disease

The booster COVID-19 dose is authenticated for administration to these people at least 6 months after completing their primary series and can be administered at any point after that time. On 23rd  August, Comirnaty (COVID-19 mRNA vaccine) was granted FDA approval to prevent coronavirus disease in individuals sixteen years of age and older.

On 25th  August 2021, the US-FDA got a supplement to the biologics license application for Comirnaty requesting approval of a single booster vaccine dose to be given about 6 months after completing primary vaccination series for people 16 years of age and older. On 17th  September, the Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting was held. The decision of the EUA amendment was taken on the basis of the available scientific evidence and a thorough review of the submitted data. It was concluded that a booster vaccine dose might effectively prevent coronavirus disease.

For supporting approval for emergency usage of a single booster vaccine dose, the US-FDA evaluated immune response and safety data from a subset of people from the original clinical trial of the coronavirus vaccine. Furthermore, the real-world data on effectiveness of vaccine over a sustained period of time was also considered.

The immune responses of 200 people (age 18-55 years) who were given a single booster dose about 6 months following their 2nd  dose were evaluated. The antibody response against the deadly COVID-19 virus 1 month following a booster vaccine dose compared to the response 1 month following the 2-dose primary series in the same people depicted a significant booster response.

Further assessments examined the rates of SARS-CoV-2 accrued during the current Delta variant rise in the people who took part in the clinical trial and finished the primary two-dose vaccination series early in the trial versus people who finished a two-dose series later in the trial. It was found that during the study period (July and August 2021), the occurrence of coronavirus infection was more in the people who finished their primary vaccine series earlier in comparison with people who finished it later.

The US-FDA found that the rate of breakthrough coronavirus disease witnessed during this time period translates to a moderate decline in the vaccine's effectiveness in people who got early vaccination. Evaluation of safety was done in 306 people (age 18-55 years) and 12 people (age 65 years and older) who were monitored for approximately 2 months. Swelling, pain, and redness at the injection site, headache, chills, fatigue, muscle pain, and joint pain were the frequently noted adverse effects by the people who were administered the booster dose of the COVID-19 vaccine.

Compared to the primary two-dose series, the booster dose of the COVID-19 vaccine exhibited more frequent swollen lymph nodes in the underarm. Notably, the FDA-authorized coronavirus vaccine is the similar formulation as the FDA-authorized Comirnaty and the vaccines can be interchangeably utilized. FDA will continue to examine the data submitted pertaining to the usage of booster doses of coronavirus vaccines and will take further decisions as appropriate.