U.S. pharmaceutical firm Pfizer and its German partner BioNTech say their COVID-19 vaccine is more than 91 percent effective for up to six months after the second dose.
No cases of the disease were observed in South Africa during the phase-three trial study among participants who had received their second dose, the companies said in a statement. "These data also provide the first clinical results that a vaccine can effectively protect against now circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population".
The trial data "provide the first clinical results that a vaccine can effectively protect against now circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population", Ugur Sahin, chief executive officer at BioNTech, said in a statement.
Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases, agreed that protection from these vaccines is likely to last longer than six months. The trial in adolescents began in October and included about 2,300 participants, half of whom received the vaccine and half that got a saltwater placebo, Joe Palca reports for NPR.
The new efficacy data, plus a safety analysis comprising data from more than 12,000 people who were fully immunized for at least six months, allow the companies to file a drug application with the FDA to turn the shot's emergency use authorization into a full approval, Pfizer CEO Albert Bourla, Ph.D., said in a statement.
Pfizer has been studying the vaccine in more than 46,000 volunteers and has noted 927 cases of confirmed Covid-19.
While neutralisation reduced 14-fold when tested against the Brazilian variant, experts believe the very high immune response generated by the vaccine is enough to provide protection against that strain.
"In South Africa, where the B.1.351 lineage is prevalent and 800 participants were enrolled, nine cases of COVID-19 were observed, all in the placebo group, indicating vaccine efficacy of 100%", the company said.
"The antibody levels were so high that they'd gone above the thresholds so they had to dilute them".
Professor Paul Moss, from the University of Birmingham and leader of the UK Coronavirus Immunology Consortium, told a briefing he was surprised how well the vaccines have worked in older people.
Both Pfizer and Moderna use a technology called messenger RNA or mRNA delivery as the basis of their vaccines. The approach has been tested against other viruses and studies in animals and people show they stimulate a strong and broad immune response.
The vaccine, which was the first in the U.S.to receive emergency use authorization from the Food and Drug Administration, is 91% effective against symptomatic disease and was even more effective at preventing severe disease, Pfizer reported.
The companies also studied a subset of teens to measure the level of virus-neutralizing antibodies a month after the second dose and found it was comparable to study participants aged 16 to 25 in the pivotal trial in adults.