People who have recovered from coronavirus infections are getting a big boost in additional immunity from a single dose of Pfizer vaccine, British researchers said on Friday.
The additional boost comes from immune cells, which do not develop at the same rate after a natural infection ̵
They found that people who were not infected needed both doses of the vaccine to see the same boost.
The team, led by Dr. Rosemary Boyton of Imperial College London, analyzed blood samples from health professionals at various stages. Some have been infected with the coronavirus and have recovered, while others have not.
The team is looking for both antibodies and immune calls, called T cells, which attack invaders, and B cells, which help produce new antibodies over time. They tested these immune responses after vaccination and tested their blood samples against variants of the virus such as B.1.1.7, first seen in the UK, and B.1.351, first seen in South Africa.
These variants have disturbing mutations in the protein of the virus, which is used to enter infected cells. B.1.351, in particular, avoids the human immune response and also appears to avoid some of the immune response elicited by vaccines.
“After a single dose, individuals with a previous infection showed enhanced T-cell immunity, antibodies secreting a memory B-cell response to the jump, and neutralizing antibodies effective against B.1.1.7 and B.1.351,” the team wrote. They found that 96% of their volunteers who were infected had already produced T cells that were targeting the virus after receiving a single dose of vaccine, compared to 70% of people who were not infected and have received only one dose of vaccine.
“In comparison, healthcare workers receiving a single dose of vaccine without prior infection show reduced immunity to variants,” they said. They found that each person’s individual genetic makeup influenced this response.
Adding a second dose of vaccine to people who have been infected does not add to the immune response. Two doses were found to significantly increase the immune response in people who did not have coronavirus. The team said their research supports the argument that coronavirus survivors only need one dose of the vaccine to enjoy full immunity.