People who have recovered from coronavirus infections get a huge boost of extra immunity from a dose of Pfizer̵
The extra boost comes from immune cells that do not develop at the same rate after natural infection – and it provides good protection against some of the worrying variants that are circulating, the researchers reported in the journal Science.
People who are not infected need both doses of the vaccine to see the same boost, they found.
The team led by Dr. Rosemary Boyton of Imperial College London analyzed blood samples from healthcare professionals at various stages. Some had been infected with coronavirus and recovered, while others had not.
The team looked for both antibodies and immune calls called T cells that attack invaders and B cells that help produce new antibodies over time. They checked 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 spike protein of the virus that are used to enter the cells it infects. B.1.351 in particular avoids the human immune response and also appears to evade some of the immune response elicited by vaccines.
“Following a dose, subjects with a previous infection showed improved T cell immunity, antibody that secretes memory B cell response at the tip, and neutralizing antibodies that are effective against B.1.1.7 and B.1.351,” the team wrote. They found that 96% of their volunteers who had become infected already produced T cells that searched for the virus after receiving a dose of vaccine, compared to 70% of the people who had not been infected and who only had received a dose of vaccine.
“By comparison, healthcare workers who received a vaccine dose without prior infection showed reduced immunity to variants,” they said. Each person’s individual genetic composition influenced this response, they found.
Addition of a second dose of vaccine to people who had become infected did not contribute to the immune response. Two doses have been shown to strengthen the immune system in people who have not had coronavirus. The team said their research supported the argument that coronavirus survivors only need one dose of vaccine to get full immunity.