In a study of more than 8,500 people from England and Wales, who did not have antibodies before their first shot and provided a total of 13,232 antibody samples, 96% developed antibodies 28 to 34 days after receiving their first dose, according to research from University College London (UCL).
The research, which is being prepared for peer review, found this figure to rise to 99% within seven and 14 days of their second shot for recipients of both vaccines, evidence that they provide protection against the coronavirus.
While those receiving the Pfizer-BioNTech vaccine developed antibodies faster than those receiving the AstraZeneca shot, rates were practically identical after a period of four weeks.
Many groups at a greater risk from Covid-19—including those with underlying conditions like diabetes and cancer, those taking immune system suppressing drugs and older adults—produced fewer antibodies after a single dose, a potential problem for countries like the U.K. where the second dose is delayed by several weeks in order to vaccinate more people.
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Spike antibodies after vaccination with Pfizer and Oxford vaccines
Covid-19: Most UK adults had antibodies after one dose of AstraZeneca or Pfizer vaccine, data suggest
https://www.bmj.com/content/373/bmj.n1274
