Alongside its partner, BioNTech, Pfizer studied two ways of updating its shots — in one case it targeted Omicron, while the other was a combination booster offering additional protection to the original vaccine.
Studies were carried out to determine whether to double the current dosage of 30mg.
The study of more than 1,200 middle-aged and older adults who had received three vaccine doses was conducted by Pfizer, which said both methods demonstrated a significant rise in the number of Omicron antibodies.
Albert Bourla, chairman and chief executive of Pfizer, said: “As we’ve said since the early days of the pandemic, we will follow the science and adapt our own approaches as needed to help address Covid-19 as the virus evolves.
“Based on this data, we believe we have two very strong Omicron-adapted candidates that elicit a substantially higher immune response against Omicron than we’ve seen to date.
“We look forward to discussing these data with the scientific community and health authorities, so we may rapidly introduce an Omicron-adapted booster as soon as possible, if authorised by regulators.”
There has been another surge in the number of Covid-19 cases in recent weeks, with the UK reporting 1.7 million cases, an increase said to be down to the rise of the BA.4 and BA.5 variants.
The European Centre for Disease Prevention and Control issued a warning last week that those strains would become dominant across the European Union, leading to a surge in case numbers.
A leading expert in the US this month said his country was grossly underestimating the number of people with Covid-19.
“It would appear official case counts are underestimating the true burden of infection by about 30-fold, which is a huge surprise,” Denis Nash, professor of epidemiology at the City University of New York School of Public Health, told The Guardian.
It was estimated by Reuters that there were currently more than 100,000 new cases each day in the US.
The Omicron-specific booster had the best results in helping the immune system to combat the variant.
Test patients who received the combination shot had an average increase of Omicron antibodies of around 9 to 11 times.
The data is set to be debated by the US Food and Drug Administration on Tuesday.