The study, led by Sheffield and Oxford Universities with support from the UK Coronavirus Immunology Consortium, and released as a pre-print on Friday, found 99% of people generate strong immune responses after one dose of the Pfizer-Biontech vaccine.
About 14 percent of the US population - or about 47 million - Americans are now fully vaccinated against COVID-19.
"This has been a long year, and I know people are exhausted and they don't want to hear that it's going to take us a little while longer, but it's going to take us a little while longer", she said.
But for people who had had Covid in the past, the first dose gave them six times the T-cell response and nearly seven times the antibody response, compared with so-called Covid "naive" people who had never been infected.
Among individuals who had not had the virus in the past and had received one dose of the jab, antibody and T cell responses were at a similar or higher level compared to those who had previously been infected but not been vaccinated.
This suggests that even in those already infected, vaccination from the Pfizer jab provides better protection and an enhanced immune response to the virus than the immune response from natural infection.
But this effect was less in people with infection-acquired immunity plus a single dose of the vaccine.
However, it is not yet known how long T cell and antibody response lasts.
"Together with our partner BioNTech, we have dosed the first healthy children in a global Phase 1/2/3 continuous study to further evaluate the safety, tolerability, and immunogenicity of the Pfizer-BioNTech COVID-19 vaccine", the company said in a statement to AFP.
The new trial, backed by the National Institutes of Health (NIH), is created to determine if the vaccine, mRNA-1273, can prevent coronavirus infection, limit virus in the nose, and reduce transmission from vaccinated individuals to their close contacts. "It does present its own challenges though with the rush, if you will, to get that".
The study, funded by the Department of Health and Social Care, was an extension of Public Health England's Siren study of healthcare workers.
For people who have not had Covid, the first dose of the vaccine provided protection equivalent to having had the virus.