Based on the available data and information, the United States Food and Drug Administration (US-FDA) took steps on 20 October 2021 for expanding the utilization of a booster dose for coronavirus vaccines in the eligible populations. FDA has amended EUA for coronavirus vaccines to permit usage of a single booster dose as shown below:

(a) At least 6 months following finalization of the primary series, a single booster dose of Moderna SARS-CoV-2 vaccine can be administered to people:

• 18-64 years of age at elevated risk of severe coronavirus disease
• 65 years of age and older
• 18-64 years of age with frequent occupational or institutional exposure to coronavirus infection

(b)  At least two months following finalization of the single-dose primary regimen, usage of a single booster dose of the Janssen SARS-CoV-2 vaccine can be administered to adults eighteen years of age and older.

(c) At least six months following completion of the primary series, a single booster dose of Pfizer-BioNTech coronavirus vaccine can be administered to people 18-64 years of age with frequent occupational or institutional exposure to coronavirus infection.

(d) Following completion of primary vaccination with another SARS-CoV-2 vaccine, each of the available SARS-CoV-2 vaccines can be used as a mix and match booster dose in eligible people.

Authorization of Janssen SARS-CoV-2 Vaccine Booster Dose

Its authorization is based on US-FDA’s assessment of immune response data in 39 people from a trial that incorporated 24 people (age 18 through 55 years of age) and 15 people (age 65 years and more). The recruited people were given a booster dose about two months following their 1st  dose, and the results showed a booster response.

About 9,000 people were administered 2 doses of Janssen SARS-CoV-2 vaccine at least 2 months apart. Out of these, about 2,700 had at least 2 months of safety follow-up following the booster dose. The safety assessment from these studies has not detected any novel safety concerns.

Authorization of Moderna SARS-CoV-2 Vaccine Booster Dose

For supporting EUA, the US-FDA examined immune response data from 149 people (age 18 years and more) from the original clinical studies who were given a booster dose at least six months following their 2nd dose. This was compared with the immune responses of 1,055 people following completion of their 2-dose series. Following 29 days, the antibody response of one hundred and forty-nine people against the virus showed a booster response following a booster dose of the vaccine.

An additional assessment from Moderna investigating the rates of coronavirus accrued during the Delta variant surge was investigated by FDA. As found, there is a waning of vaccine efficacy with time. Determination of safety was done in 171 people (age 18 years and more) who were followed for an average of about 6 months. Fever,  headache, pain at the injection site,  tiredness,  joint pain, vomiting,  muscle pain, chills,  nausea, swollen lymph nodes in the same arm as the injection were the commonly noted adverse effects in people receiving booster doses. Swollen lymph nodes present in the underarm were noted more commonly after the booster dose when compared to primary two-dose series.

The ongoing assessment from FDA and Centers for Disease Control and Prevention (CDC) safety surveillance systems have found elevated risks of pericarditis, inflammatory heart conditions and myocarditis after vaccination with the 2nd  dose of Moderna coronavirus vaccine. The single booster dose of Moderna vaccine is half of the dose that is given for a primary series dose and is given at least 6 months following accomplishment of vaccine's primary series.

Authorization of mix and match/heterologous booster dose

For the currently available coronavirus vaccines, US-FDA has approved the use of heterologous booster doses. A single booster dosage of any of the available coronavirus vaccines can be given as a mix and match booster dosage after execution of primary vaccination with a different  coronavirus vaccine. For the heterologous booster dose, the eligible population and the dosing interval are similar to those approved for the booster dosage of vaccine utilized for primary vaccination.

In the fight against the coronavirus pandemic, vaccination appears to be the safest and most efficacious way for preventing coronavirus-associated hospitalization and death. The current data suggests waning immunity in some people who are completely vaccinated. Thus, the availability of authorized boosters is essential for persistent protection against SARS-CoV-2.