Pfizer and BioNTech have filed an application seeking emergency use authorization (EUA) from the US Food and Drug Administration (FDA) for an additional booster dose of their Covid-19 vaccine in older adults.

The additional booster is intended for usage in adults of the age 65 years and above who have previously received an initial booster shot of any authorised or approved Covid-19 vaccines.

Currently, only a single booster dose of the vaccine is authorised to be given a minimum of five months following the initial two-dose vaccine regimen in people aged 12 years and above.

The latest filing is based on two real-world data sets from Israel evaluated when the Omicron variant of the SARS-CoV-2 virus was prevalent.

Pfizer noted that both these data sets offered evidence that additional mRNA booster enhances immunogenicity and reduces confirmed infections and severe disease rates. 

In addition, an assessment of Israeli Ministry of Health records was carried out in more than 1.1 million adults of the age 60 years and above without a history of Covid-19 and eligible to receive a fourth vaccine dose or the additional booster.

The fourth dose of the Pfizer-BioNTech Covid-19 vaccine was given a minimum of four months following the initial booster shot.

According to the findings, the confirmed infection and severe disease rates were reduced two and four times respectively in people who were given the additional booster versus those who were given only one booster shot.

The latest submission also comprises data from an open-label, non-randomised trial underway at one Israel trial site in healthcare workers of the age 18 years and above who received three vaccines doses.

In 154 study subjects, neutralising antibody titers rose nearly seven to eight-fold at two and three weeks following the administration of additional booster vaccine dose as against five months following the third dose.

Furthermore, at one and two weeks after the fourth vaccine, an eight-fold and ten-fold surge in neutralising antibody titers against Omicron, respectively, was observed versus five months following the initial booster vaccine.

No new safety issues were reported in people who received the fourth vaccine dose.

Last month, Pfizer and BioNTech announced the extension of their rolling submission to the FDA for amending the Covid-19 vaccine EUA to include children of the age six months to four years.