A single dose of vaccine increases protection against various variants of SARS-COV-2 coronavirus, but only for those who have previously overcome COVID-19. The real effectiveness of the vaccine against new strains was revealed by scientists of the Imperial College of London, whose article was published in the journal Science.
Experts analyzed blood samples taken from health workers in Barts hospitals and Royal Fri after introducing the first dose of Pfizer / Biontech vaccine. The level of immunity (antibodies, in-cell memory and T-killers) was rated against the source strain of SARS-COV-2, as well as a Kent strain dominant in the UK, and a strain from South Africa.
Researchers have found that people who have previously had an easy or asymptomatic infection, after a single dose of RNA-vaccine, protection against African and British strains has significantly increased. However, those who have not previously had COVID-19, the immune response was weaker after the first dose, which potentially subjected their risk of infection with new virus options.
It remains unclear which level of protection is provided by T cells. Mutations in the Kent and South African strains could reduce T-cell immunity, to strengthen it or not to affect it in comparison with the original strain, depending on genetic differences between people.