People who have been ill with COVID-19 can make just one injection of the coronavirus vaccine to develop strong immunity against infection. This is reported in an article published in the journal JAMA Network Open.
The study involved 29 people who were confirmed to have a coronavirus infection by PCR analysis and 30 people who were not sick with COVID-19. The average age of the volunteers was 42 years, and three-quarters of the participants were women.
The researchers found more antibodies against SARS-CoV-2 in previously infected people after the first dose of the Pfizer vaccine than in people not infected with the coronavirus after both doses. At the same time, the second dose for those who were ill did not give any additional benefits and did not increase the number of antibodies in the blood additionally.
A previous infection by itself is not a reliable protection against COVID-19. The concentration of antibodies in people who had previously encountered coronavirus in blood samples was about 621 units per milliliter (AU/ml). After the first dose of the Pfizer vaccine, this level increased to 30,000 AU/ml, which provides the necessary protection against infection. Thus, scientists call one dose of the vaccine optimal for those who have been ill.