Now that vaccine rates have started to slow in the U.S., you might have a better chance at choosing exactly which vaccine you want to get by setting up your appointment at a specific location. Fortunately, experts say that all three of the vaccines authorized for emergency use in the U.S. are safe and effective, and multiple studies have confirmed this. However, a new discovery may make Pfizer's vaccine look even more promising: Research has found that 96 percent of people who get the Pfizer vaccine develop COVID antibodies after just one dose.
Researchers from University College London and the National Health Service (NHS) analyzed the antibody response of more than 8,500 people from England and Wales who received either the Pfizer or AstraZeneca vaccine and did not have antibodies before their shot. They published the preliminary results for their study on May 14.
According to their findings, 96.42 percent of those who received either the Pfizer or AstraZeneca vaccine developed antibodies 28 to 34 days after just their first dose. "A single dose of the AstraZeneca or Pfizer vaccine leads to high antibody levels in people that have not previously had COVID-19," the researchers explain.
Antibodies also developed faster in participants who received the Pfizer vaccine, but by four weeks after the first vaccine dose, the antibody rates were equivalent for both shots.
"Over nine out of 10 adults in the UK who had either the Pfizer or AstraZeneca vaccine produced antibodies against the virus within a month of their first shot," study lead author Maddie Shrotri said in a statement. "How well these vaccines work is remarkable, especially given the speed at which they've been developed. It's a real feat of science in the face of the most devastating pandemic in a century."
Antibody levels following the first dose of either vaccine were not as high in some recipients, however. For instance, the researchers say they "found evidence that antibody levels were lower with increasing age following the first dose of vaccine." And people with various long-term health conditions such as diabetes, heart disease, cancer, and those on immunosuppressive therapies also experienced lower antibody levels following the first dose.
"These observed differences in antibody levels highlight the importance of ongoing public health preventative measures such as social distancing for adults who have only had one dose of vaccine, particularly those who are older and more clinically vulnerable," the researchers state in the study.
The conclusion, then, is not that there isn't a clear need for the second dose of these vaccines. The researchers reported that an even higher number of people—99.08 percent—developed antibodies within seven to 14 days after receiving their second shot of either vaccine. The study also found that high antibody levels were "observed for nearly all individuals" after the second dose of the Pfizer or AstraZeneca vaccine, including those with long-term health conditions. According to the researchers, this reinforces the "importance of full coverage of this second dose for the population."