Washington, Apr 2 (IANS): The ongoing Phase 3 clinical trial of the Pfizer/BioNTech's Covid-19 vaccine showed that it remains highly effective for up to six months after the second dose, the two companies announced.

Results from the analysis of 927 confirmed symptomatic coronavirus cases observed in their pivotal Phase 3 study showed the Pfizer-BioNTech vaccine, BNT162b2, was 91.3 per cent effective against the disease, measured seven days through up to six months after the second dose, Xinhua news agency reported citing a joint statement issued by the companies on Thursday.

The vaccine was 100 per cent effective against severe disease as defined by the US Centers for Disease Control and Prevention, and 95.3 per cent effective against severe Covid-19 as defined by the Food and Drug Administration (FDA), according to the statement.

Safety data from the Phase 3 study have been collected from more than 12,000 vaccinated participants who have a follow-up time of at least six months after the second dose, demonstrating a favourable safety and tolerability profile, it added.

"These data confirm the favorable efficacy and safety profile of our vaccine and position us to submit a Biologics License Application to the US FDA," said Albert Bourla, Chairman and CEO of Pfizer.

"These data also provide the first clinical results that a vaccine can effectively protect against currently circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population," Ugur Sahin, CEO and co-founder of BioNTech, was quoted as saying in the statement.

The new results came a day after the two companies announced that the vaccine has demonstrated 100 per cent efficacy and robust antibody responses in a trial in adolescents 12 to 15 years of age.

The trial enrolled 2,260 adolescents in the age group in the US.

In the trial, 18 cases of Covid-19 were observed in the placebo group versus none in the vaccinated group.

The vaccine elicited SARS-CoV-2-neutralising antibody geometric mean titers (GMTs) of 1,239.5, demonstrating strong immunogenicity in a subset of adolescents one month after the second dose, according to the companies.

The results exceeded those recorded earlier in vaccinated participants aged 16 to 25 years old, according to the trial data.

The two companies plan to submit these data to the FDA and the European Medicines Agency as soon as possible to request expansion of the Emergency Use Authorization and EU Conditional Marketing Authorization for BNT162b2.

The FDA authorised the Pfizer-BioNTech Cvaccine for emergency use in the US in December last year.

The vaccine, the first one to receive an FDA approval in the country, was authorised for use in individuals 16 years of age and older.